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Sample records for eastern dharwar craton

  1. 207Pb-206Pb zircon ages of eastern and western Dharwar craton, southern India : Evidence for contemporaneous Archaean crust

    Science.gov (United States)

    Maibam, B.; Goswami, J. N.; Srinivasan, R.

    2009-04-01

    Dharwar craton is one of the major Archaean crustal blocks in the Indian subcontinent. The craton is comprised of two blocks, western and eastern. The western domain is underlain by orthogneisses and granodiorites (ca. 2.9-3.3 Ga) collectively termed as Peninsular Gneiss [e.g., 1] interspersed with older tracts of metasedimentary and metamorphosed igneous suites (Sargur Group and Dharwar Group; [2]). The eastern part of the craton is dominated by Late Archaean (2.50-2.75 Ga) granitoids and their gneissic equivalents. They are interspersed with schist belts (also of Sargur Group and Dharwar Group), which are lithologically similar to the Dharwar Supergroup in the western block, but are in different metamorphic dress. Here we report 207Pb-206Pb age of zircons separated from the metasedimentary and gneissic samples from the two blocks to constrain the evolution of the Dharwar craton during the early Archaean. Detrital zircons of the metasedimentary rocks from both the blocks show a wide range of overlapping ages between ~2.9 to >3.5 Ga. Zircon ages of the orthogneisses from the two blocks showed that most of the analysed grains of the eastern Dharwar block are found to be of the age as old as the western Dharwar gneisses. Imprints of younger events could be discerned from the presence of overgrowths in zircons from the studied samples throughout the craton. Our data suggest that crust forming cycles in the two blocks of the Dharwar craton occurred contemporaneously during the Archaean. References [1] Beckinsale, R.D., Drury, S.A., Holt, R.W. (1980) Nature 283, 469-470. [2] Swami Nath J., Ramakrishnan M., Viswanatha M.N. (1976) Rec. Geol. Surv. Ind., 107, 149-175.

  2. The 1000Ma reassembly of Dharwar and Bastar cratons – Evidence ...

    Indian Academy of Sciences (India)

    8

    2. General Geology. The geology of the study area comprises of the rocks of the Dharwar craton, the ...... Craton-mobile belt relations in in Southern Granulite Terrain. Geol. Soc. .... chemistry: a case study from the Eastern Ghats Belt. India.

  3. Continental lithospheric evolution: Constraints from the geochemistry of felsic volcanic rocks in the Dharwar Craton, India

    Science.gov (United States)

    Manikyamba, C.; Ganguly, Sohini; Saha, Abhishek; Santosh, M.; Rajanikanta Singh, M.; Subba Rao, D. V.

    2014-12-01

    Felsic magmatism associated with ocean-ocean and ocean-continent subduction processes provide important evidence for distinct episodes of crust-generation and continental lithospheric evolution. Rhyolites constitute an integral component of the tholeiitic to calc-alkaline basalt-andesite-dacite-rhyolite (BADR) association and contribute to crustal growth processes at convergent plate margins. The evolution of the Dharwar Craton of southern peninsular India during Meso- to Neoarchean times was marked by extensive development of greenstone belts. These granite-greenstone terranes have distinct volcano-sedimentary associations consistent with their geodynamic setting. The present study deals with geochemistry of rhyolites from the Chitradurga-Shimoga greenstone belts of western (WDC) and the Gadwal-Kadiri greenstone belts of eastern (EDC) sectors of Dharwar Craton to compare and evaluate their petrogenesis and geodynamic setting and their control on the continental lithospheric evolution of the Dharwar Craton. At a similar range of SiO2, Al2O3, Fe2O3, the rhyolites of WDC are more potassic, whereas the EDC rhyolites are more sodic and less magnesian with slight increase in TiO2. Minor increase in MgO content of WDC rhyolites reflects their ferromagnesian trace elements which are comparatively lower in the rhyolites of EDC. The relative enrichment in LILE (K, Rb) and depletion in HFSE (Nb, Ta, Zr, Hf) marked by negative Nb-Ta, Zr-Hf and Ti anomalies endorse the convergent margin processes for the generation of rhyolites of both the sectors of Dharwar Craton. The high silica potassic rhyolites of Shimoga and Chitradurga greenstone belts of WDC showing prominent negative Eu and Ti anomalies, flat HREE patterns correspond to Type 3 rhyolites and clearly point towards their generation and emplacement in an active continental margin environment. The geochemical characteristics of Gadwal and Kadiri rhyolites from eastern Dharwar Craton marked by aluminous compositions with

  4. New paleomagnetic results on ˜ ˜2367 Ma Dharwar giant dyke swarm, Dharwar craton, southern India: implications for Paleoproterozoic continental reconstruction

    Science.gov (United States)

    Babu, N. Ramesh; Venkateshwarlu, M.; Shankar, Ravi; Nagaraju, E.; Parashuramulu, V.

    2018-02-01

    Here we report new paleomagnetic results and precise paleopole position of the extensional study on ˜ 2367 Ma mafic giant radiating dyke swarm in the Dharwar craton, southern India. We have sampled 29 sites on 12 dykes from NE-SW Karimnagar-Hyderabad dykes and Dhone-Gooty sector dykes, eastern Dharwar craton to provide unambiguous paleomagnetism evidence on the spectacular radiating dyke swarm and thereby strengthening the presence of single magmatic event at ˜ 2367 Ma. A total of 158 samples were subjected to detailed alternating field and thermal demagnetization techniques and the results are presented here along with previously reported data on the same dyke swarm. The remanent magnetic directions are showing two components, viz., seven sites representing four dykes show component (A) with mean declination of 94{{}°} and mean inclination of - 70{{}°} (k=87, α_{95}=10{{}°}) and corresponding paleopole at 16{{}°}N, 41{{}°}E (dp=15{{}°} and dm=17{{}°}) and 22 sites representing 8 dykes yielded a component (B) with mean declination of 41{{}°} and mean inclination of - 21{{}°} (k=41, α_{95}=9{{}°}) with a paleopole at 41{{}°}N, 200{{}°}E (dp=5{{}°} and dm=10{{}°}). Component (A) results are similar to the previously reported directions from the ˜ 2367 Ma dyke swarm, which have been confirmed fairly reliably to be of primary origin. The component (B) directions appear to be strongly overprinted by the 2080 Ma event. The grand mean for the primary component (A) combined with earlier reported studies gives mean declination of 97{{}°} and mean inclination of - 79{{}°} (k=55, α_{95}=3{{}°}) with a paleopole at 15{{}°}N, 57{{}°}E (dp=5{{}°}, dm=6{{}°}). Paleogeographical position for the Dharwar craton at ˜ 2367 Ma suggests that there may be a chance to possible spatial link between Dharwar dykes of Dharwar craton (India), Widgemooltha and Erayinia dykes of Yilgarn craton (Australia), Sebanga Poort Dykes of Zimbabwe craton (Africa) and Karelian

  5. U-Pb SHRIMP ages of detrital zircons from Hiriyur formation in Chitradurga Greenstone belt and its implication to the Neoarchean evolution of Dharwar craton, South India

    International Nuclear Information System (INIS)

    Nasheeth, A.; Okudaira, T.; Horie, K.; Hokada, T.; Satish Kumar, M.

    2016-01-01

    We report newly obtained U-Pb SHRIMP ages of detrital zircons from metagreywackes in the Hiriyur Formation (Chitradurga Group, Dharwar Supergroup) from the central eastern part of the Chitradurga greenstone belt. U-Pb analyses yield three major Neoarchean age populations ranging from 2.70 - 2.54 Ga with some minor age population of Mesoarchean. The maximum age of deposition is constrained by the youngest detrital zircon population at 2546 Ma. This is the first report of the occurrence of supracrustal rocks less than 2.58 Ga in the central part of Chitradurga greenstone belt. Close evaluation of detrital ages with the published ages of surrounding igneous rocks suggest that the youngest detrital zircons might be derived from rocks of the Eastern Dharwar craton and the inferred docking of the western and eastern Dharwar cratons happened prior to the deposition of the Hiriyur Formation. The Chitradurga shear zone, dividing the Dharwar craton into western and eastern blocks, probably developed after the deposition. Furthermore, the lower intercept is interpreted as evidence for the Pan-African overprints in the study area. (author)

  6. ∼2.5 Ga late cratonisation events in Dharwar craton: insights from the gold mineralisation ages

    International Nuclear Information System (INIS)

    Srinivasa Sarma, D.; Ram Mohan, M.; McNaughton, Neal

    2013-01-01

    The history of volcanism, granitic magmatism, and gold mineralization is defined by U-Pb geochronology of magmatic zircons and hydrothermal monazite and xenotime respectively. The felsic volcanic host rocks from Hutti greenstone belt have a U-Pb zircon age of 258 ±7 Ma, about 40 m.y. older than the age of gold mineralization at 2547±10 Ma determined from hydrothermal monazite in the Hutti gold deposit. The syntectonic Kavital granitoid in the Hutti greenstone belt has a U-Pb zircon age of 2545±7 Ma, which overlaps with the timing of gold deposition and is consistent with structural interpretations. Zircon U-Pb ages for a felsic volcanic rock (2,588±10 Ma) and an intrusive granite (e''2,555±6 Ma) in the Gadag greenstone belt in the Western Dharwar Craton. In situ U-Pb dating of monazite and xenotime in gold reefs of the Gadag (2,522±6 Ma) and Ajjanahalli (2,520±9 Ma) gold deposits reveal a previously undated episode of gold mineralization at 2.52 Ga, substantially younger than the 2.55 Ga Hutti deposit in the eastern Dharwar Craton. The Hutti, Gadag and Ajjanahalli gold geochronology suggests that gold mineralization occurred throughout the Dharwar craton some 80 to 120 m.y. later than the major peak of Late Archean world-class orogenic gold mineralization in most other Archean cratons. Although gold mineralization across the craton postdates most of the magmatic activity and metamorphism at upper crustal levels, widespread thermal reworking of the lower middle crust, involving partial melting, metamorphism, and lower crustal granitoid intrusion, occurred concurrently with gold mineralization. It is likely that the large-scale hydrothermal fluid flow that produced widespread gold deposition was also part of this tectono-thermal event during the final stages of cratonization of the Dharwar Craton in southern India. (author)

  7. Seismically imaged shallow and deep crustal structure and potential field anomalies across the Eastern Dharwar Craton, south Indian shield: Possible geodynamical implications

    Science.gov (United States)

    Pandey, O. P.; Chandrakala, K.; Vasanthi, A.; Kumar, K. Satish

    2018-05-01

    The time-bound crustal evolution and subsequent deformation of the Cuddapah basin, Nellore Schist Belt and Eastern Ghats terrain of Eastern Dharwar Craton, which have undergone sustained geodynamic upheavals since almost 2.0 billion years, remain enigmatic. An attempt is made here to integrate newly available potential field data and other geophysical anomalies with deep seismic structure, to examine the generative mechanism of major crustal features, associated with this sector. Our study indicates that the initial extent of the Cuddapah basin sedimentation may have been much larger, extending by almost 50-60 km west of Tadipatri during Paleoproterozoic period, which subsequently shrank due to massive erosion following thermal uplift, caused by SW Cuddapah mantle plume. Below this region, crust is still quite warm with Moho temperatures exceeding 500 °C. Similarly, Nallamalai Fold Belt rocks, bounded by two major faults and extremely low gravity, may have occupied a large terrain in western Cuddapah basin also, before their abrasion. No geophysical signatures of thrusting are presently seen below this region, and thus it could not be an alien terrain either. In contrast, Nellore Schist Belt is associated with strikingly high positive gravity, possibly caused by a conspicuous horst structure and up dipping mafic crustal layers underneath, that resulted due to India-east Antarctica collision after the cessation of prolonged subduction (1.6-0.95 Ga). Further, the crustal seismic and gravity signatures would confirm presence of a totally distinct geological terrain east of the Cuddapah basin, but the trace of Eastern Ghats Belt is all together missing. Instead, all the geophysical signatures, point out to presence of a Proterozoic sedimentary terrain, east of Nellore Schist Belt. It is likely that the extent of Prorerozoic sedimentation was much larger than thought today. In addition, presence of a seismically detected Gondwana basin over Nellore Schist Belt, apart

  8. Origin and diamond prospectivity of Mesoproterozoic kimberlites from the Narayanpet field, Eastern Dharwar Craton, southern India

    DEFF Research Database (Denmark)

    Chalapathi Rao, N.V.; Paton, Chad; Lehmann, B.

    2012-01-01

    to both archetypal kimberlites and to orangeites, and it is not straight forward to apply conventional mineral-genetic schemes in the nomenclature of the NKF pipes. Low fO of the NKF magma (ΔNNO (nickel-nickel oxide)=-1.9 to -3.2), indistinguishable from that of diamondiferous kimberlites world-wide...... is a characteristic feature of the NKF. This has been attributed alternately to the derivation of NKF magmas from a shallower depth, or to variability in thickness of the Sub-Continental Lithospheric Mantle (SCLM) beneath the Eastern Dharwar Craton. Recently, exploration by De Beers resulted in the discovery...... of a number of new kimberlite occurrences from the NKF, with some of their geochemical features and radiogenic isotope systematics subsequently becoming available. In this paper, we present detailed petrography, groundmass mineral composition and new bulk-rock geochemistry data for a number of NKF rocks...

  9. Magmatism during the accretion of the late Archaean Dharwar Craton (South India): sanukitoids and related rocks in their geological context.

    Science.gov (United States)

    Moyen, J.-F.; Martin, H.; Jayananda, M.; Peucat, J.-J.

    2003-04-01

    The South Indian Dharwar Craton assembled during the late-Archaean (ca. 2.5 Ga). This event was associated with intense granite genesis and emplacement. Based on petrography and geochemistry, 4 main types of late Archaean granitoids were distinguished: (1) Anatectic granites (and diatexites), formed by partial melting of TTG gneisses; (2) Classical TTGs; (3) Sanukitoids, generated by interaction between slab melts (TTG) and mantle peridotite; (4) The high HFSE Closepet granite, interpreted as derived from partial melting of a mantle metasomatized by slab melts (TTG). While the 3 later groups all are interpreted as resulting from slab melt/mantle wedge interactions, their differences are related to decreasing felsic melt/peridotite ratios during the ascent “slab melts” in the mantle wedge above an active subduction zone. Field data together with geochronology and isotope geochemistry allow to subdivide the Dharwar craton into three main domains: (1) The Western Dharwar Craton (WDC) is an old (3.3 2.9 Ga ), stable continental block with limited amounts of 2.5 Ga old anatectic granites. (2) The Eastern Dharwar Craton (EDC) is subdivided into two parts: (2a) West of Kolar Schist Belt, a region of 3.0-2.7 Ga old basement intruded by 2.5 Ga old anatectic granites; (2b) East of Kolar, an area featuring mainly 2.5 Ga old diatexites and granites, derived of partial melting of a newly accreted TTG crust. Anatectic granites are ubiquitous, and late in the cratonic evolution; they witnessed generalized melting of a juvenile crust. In contrast, deep-originated granites emplaced before this melting and are restricted to the boundaries between the blocks. This structure of distinct terranes separated by narrow bands operating as channels for deep-originated magmas provides independent evidences for a two-stage evolution: an arc accretion context for the TTG, sanukitoids and related rocks, immediately followed by high temperature reworking of the newly accreted craton

  10. Paleomagnetism and geochronological studies on a 450 km long 2216 Ma dyke from the Dharwar craton, southern India

    Science.gov (United States)

    Nagaraju, E.; Parashuramulu, V.; Kumar, Anil; Srinivas Sarma, D.

    2018-01-01

    Paleomagnetic and geochronological studies were carried out on a ∼ 450 km long (from 17 sites) N-S striking Paleoproterozoic dyke swarm exposed along a natural crustal cross section of about 10 km (increasing from North to South) in the Dharwar Craton, to study the characteristics of paleomagnetism and geochronology in vertical dimension. U-Pb/Pb-Pb dating on baddeleyite gives a crystallisation age of 2216.0 ± 0.9 Ma for long dyke AKLD. Paleomagnetic data from this well dated ∼ 2216 Ma dyke swarm in Dharwar Craton are of excellent quality. High coercivity and high blocking temperature components are carried by single domain magnetite and show dual polarity remanence directions. Combined normal and reverse polarity remanences on AKLD and other N-S dykes define the most reliable paleomagnetic pole for ∼ 2216 Ma at latitude 36°S and longitude 312°E (A95 = 7°). Though paleomagnetic data is unavailable on other N-S dykes below the Cuddapah basin, high precision geochronology suggest that they are of similar age within errors. Though there is a variation in the crustal depth of Dharwar craton from north to south, consistent Pb-Pb/U-Pb baddeleyite geochronology and paleomagnetic studies along the AKLD established its continuity and preservation along its entire strike length. The virtual geomagnetic poles of these sites confirm a stable remanence and are almost identical to the previously reported paleomagnetic pole and also supported by positive reversal test. Positive paleomagnetic reversal test on these dykes signify that the remanent magnetization is primary and formed during initial cooling of the intrusions. Updated apparent polar wander path of Dharwar craton indicates relatively low drift rate during 2.21-2.08 Ga interval. Magnetogranulometry and SEM studies show that remanent magnetization in this dyke was carried by single domain magnetite residing within silicate minerals.

  11. Evolution of the Dharwar Craton: a terrain of early Archean crustal stability, long term orogenic cycles and large scale palaeobiological activity

    International Nuclear Information System (INIS)

    Srinivasan, R.; Naqvi, S.M.

    1988-01-01

    Traceable history of the Dharwar Craton goes back to approximately 3400 m.y. old tonalitic to trondhjemitic fundamental gneiss whose REE composition indicates its derivation from a preexisting basalt which apparently had very short time of crustal residence. The fundamental gneiss is preserved only as rare relicts in the vast gneissic complex of the Indian Peninsula (the Peninsular Gneiss), and as pebbles in the conglomerates of the Archean Dharwar sequence. Study of these relicts, shows evidence of a deformation episode prior to the deposition of the high- and low-grade Dharwar supracrustal sequence. The Dharwar supracrustal sequence is briefly described. Geochemistry of the volcanic and sedimentary rocks of the Dharwar supracrustal belts are examined

  12. Contrasting isotopic mantle sources for proterozoic lamproites and kimberlites from the Cuddapah basin and eastern Dharwar craton: implication for proterozoic mantle heterogeneity beneath southern India

    International Nuclear Information System (INIS)

    Chalapathi Rao, N.V.; Gibson, S.A.; Pyle, D.M.; Dickin, A.P.

    1998-01-01

    Kimberlites intruding the Precambrian basement towards the western margin of the Cuddapah basin near Anantapur (1090 Ma) and Mahbubnagar (1360 Ma) in Andhra Pradesh have initial 87 Sr/ 86 Sr between 0.70205 to 0.70734 and σNd between +0.5 to +4.68. Mesoproterozoic lamproites (1380 Ma) from the Cuddapah basin (Chelima and Zangamarajupalle) and its NE margin (Ramannapeta) have initial 87 Sr/ 86 Sr between 0.70520 and 0.7390 and εNd from -6.43 to -8.29. Combined Sr- and Nd- isotopic ratios suggest that lamproites were derived from enriched sources which have time-averaged higher Rb/Sr and lower Sm/Nd ratios than the Bulk Earth whereas kimberlites were derived from depleted source with lower Rb/Sr and higher Sm/Nd ratios. Calculated T DM model ages suggest that the lamproite source enrichment (∼2 Ga) preceded that of kimberlites (∼1.37 Ga). Our work demonstrates the existence of isotopically contrasting upper mantle sources for southern Indian kimberlites and lamproites and provides evidence for a lateral, isotopically heterogeneous mantle beneath the Cuddapah basin and eastern Dharwar craton. The significance of our results in the context of diamond exploration is also highlighted. (author)

  13. Nature and source of the ore-forming fluids associated with orogenic gold deposits in the Dharwar Craton

    Directory of Open Access Journals (Sweden)

    Biswajit Mishra

    2018-05-01

    Full Text Available Neoarchean orogenic gold deposits, associated with the greenstone-granite milieus in the Dharwar Craton include (1 the famous Kolar mine and the world class Hutti deposit; (2 small mines at Hira-Buddini, Uti, Ajjanahalli, and Guddadarangavanahalli; (3 prospects at Jonnagiri; and (4 old mining camps in the Gadag and Ramagiri-Penakacherla belts. The existing diametric views on the source of ore fluid for formation of these deposits include fluids exsolved from granitic melts and extracted by metamorphic devolatilization of the greenstone sequences. Lode gold mineralization occurs in structurally controlled higher order splays in variety of host rocks such as mafic/felsic greenstones, banded iron formations, volcaniclastic rocks and granitoids. Estimated metamorphic conditions of the greenstones vary from lower greenschist facies to mid-amphibolite facies and mineralizations in all the camps are associated with distinct hydrothermal alterations. Fluid inclusion microthermometric and Raman spectroscopic studies document low salinity aqueous-gaseous (H2O + CO2 ± CH4 + NaCl ore fluids, which precipitated gold and altered the host rocks in a narrow P–T window of 0.7–2.5 kbar and 215–320 °C. While the calculated fluid O- and C-isotopic values are ambiguous, S-isotopic compositions of pyrite-precipitating fluid show distinct craton-scale uniformity in terms of its reduced nature and a suggested crustal sulfur source.Available ages on greenstone metamorphism, granitoid plutonism and mineralization in the Hutti Belt are tantamount, making a geochronology-based resolution of the existing debate on the metamorphic vs. magmatic fluid source impossible. In contrast, tourmaline geochemistry suggests involvement of single fluid in formation of gold mineralization, primarily derived by metamorphic devolatilization of mafic greenstones and interlayered sedimentary rocks, with minor magmatic contributions. Similarly, compositions of scheelite

  14. Neoproterozoic extension in the greater dharwar craton: A reevaluation of the "betsimisaraka suture" in madagascar

    Science.gov (United States)

    Tucker, R.D.; Roig, J.-Y.; Delor, C.; Amlin, Y.; Goncalves, P.; Rabarimanana, M.H.; Ralison, A.V.; Belcher, R.W.

    2011-01-01

    The Precambrian shield of Madagascar is reevaluated with recently compiled geological data and new U-Pb sensitive high-resolution ion microprobe (SHRIMP) geochronology. Two Archean domains are recognized: the eastern Antongil-Masora domain and the central Antananarivo domain, the latter with distinctive belts of metamafic gneiss and schist (Tsaratanana Complex). In the eastern domain, the period of early crust formation is extended to the Paleo-Mesoarchean (3.32-3.15 Ga) and a supracrustal sequence (Fenerivo Group), deposited at 3.18 Ga and metamorphosed at 2.55 Ga, is identified. In the central domain, a Neoarchean period of high-grade metamorphism and anatexis that affected both felsic (Betsiboka Suite) and mafic gneisses (Tsaratanana Complex) is documented. We propose, therefore, that the Antananarivo domain was amalgamated within the Greater Dharwar Craton (India + Madagascar) by a Neoarchean accretion event (2.55-2.48 Ga), involving emplacement of juvenile igneous rocks, high-grade metamorphism, and the juxtaposition of disparate belts of mafic gneiss and schist (metagreenstones). The concept of the "Betsimisaraka suture" is dispelled and the zone is redefined as a domain of Neoproterozoic metasedimentary (Manampotsy Group) and metaigneous rocks (Itsindro-Imorona Suite) formed during a period of continental extension and intrusive igneous activity between 840 and 760 Ma. Younger orogenic convergence (560-520 Ma) resulted in east-directed overthrusting throughout south Madagascar and steepening with local inversion of the domain in central Madagascar. Along part of its length, the Manampotsy Group covers the boundary between the eastern and central Archean domains and is overprinted by the Angavo-Ifanadiana high-strain zone that served as a zone of crustal weakness throughout Cretaceous to Recent times.

  15. Zircon U-Pb ages and Hf isotopic compositions of neoarchaean granitoids from Karimnagar, Eastern Dharwar craton, Southern India: LA-ICPMS results

    International Nuclear Information System (INIS)

    Babu, E.V.S.S.K.; Vijaya Kumar, T.; Sreenivas, B.; Khadke, Namrata; Vijaya Gopal, B.; Bhaskar Rao, Y.J.

    2015-01-01

    The Archaean Dharwar and Bastar cratons of Peninsular India are separated by the NE-SW trending Godavari Graben. This zone is involved in recurrent rifting. It is generally believed that earlier phase of rifting dates back to Mesoproterozoic and the younger phase is related to the deposition of Permo-carboniferous coal-bearing sediments. A belt of high-grade rocks (∼ 150 x 45 km) - the Karimnagar granulite terrane (KGT) along the southern flank of the graben. The KGT comprises high-grade lithologies such as orthopyroxene-bearing quarto-feldspathic gneiss, amphibolite-granulite facies supracrustal belts that include metamorphosed quartz-arenites, pelites, carbonates, iron formation and mafic rocks as well as several zones of migmatite and younger granitoid intrusives. The study presented new LA-ICPMS zircon U-Pb age data for five granitoid (charnockite and granite) samples (KRN-90-24, KRN-90-30, KRN-13-02, KRN-13-03 and KRN-13-05; a closer constraint of the age crystallization of protoliths and high-grade metamorphism of felsic granulites and orthogneisses from the KGT. Hf isotopic compositions were also obtained for selected zircons from two samples (KRN-90-24 and KRN-90-30) using New Wave UP-213 Laser Ablation system coupled to Nu Plasma HR MC-ICPMS to constraint the nature of the felsic protoliths of the charnockite and granite gneisses in the KGT

  16. Platinum Group Elements (PGE) geochemistry of komatiites and boninites from Dharwar Craton, India: Implications for mantle melting processes

    Science.gov (United States)

    Saha, Abhishek; Manikyamba, C.; Santosh, M.; Ganguly, Sohini; Khelen, Arubam C.; Subramanyam, K. S. V.

    2015-06-01

    High MgO volcanic rocks having elevated concentrations of Ni and Cr are potential hosts for platinum group elements (PGE) owing to their primitive mantle origin and eruption at high temperatures. Though their higher PGE abundance is economically significant in mineral exploration studies, their lower concentrations are also valuable geochemical tools to evaluate petrogenetic processes. In this paper an attempt has been made to evaluate the PGE geochemistry of high MgO volcanic rocks from two greenstone belts of western and eastern Dharwar Craton and to discuss different mantle processes operative at diverse geodynamic settings during the Neoarchean time. The Bababudan greenstone belt of western and Gadwal greenstone belt of eastern Dharwar Cratons are dominantly composed of high MgO volcanic rocks which, based on distinct geochemical characteristics, have been identified as komatiites and boninites respectively. The Bababudan komatiites are essentially composed of olivine and clinopyroxene with rare plagioclase tending towards komatiitic basalts. The Gadwal boninites contain clinopyroxene, recrystallized hornblende with minor orthopyroxene, plagioclase and sulphide minerals. The Bababudan komatiites are Al-undepleted type (Al2O3/TiO2 = 23-59) with distinctly high MgO (27.4-35.8 wt.%), Ni (509-1066 ppm) and Cr (136-3036 ppm) contents. These rocks have low ΣPGE (9-42 ppb) contents with 0.2-2.4 ppb Iridium (Ir), 0.2-1.4 ppb Osmium (Os) and 0.4-4.4 ppb Ruthenium (Ru) among Iridium group PGE (IPGE); and 1.4-16.2 ppb Platinum (Pt), 2.8-19 ppb Palladium (Pd) and 0.2-9.8 ppb Rhodium (Rh) among Platinum group PGE (PPGE). The Gadwal boninites are high-Ca boninites with CaO/Al2O3 ratios varying between 0.8 and 1.0, with 12-24 wt.% MgO, 821-1168 ppm Ni and 2307-2765 ppm Cr. They show higher concentration of total PGE (82-207 ppb) with Pt concentration ranging from 13 to 19 ppb, Pd between 65 and 180 ppb and Rh in the range of 1.4-3 ppb compared to the Bababudan komatiites. Ir

  17. Magnetic anomalies across Bastar craton and Pranhita–Godavari ...

    Indian Academy of Sciences (India)

    Such intrusions can be explained considering the collision of the Bastar and Dharwar cratons by the ... that there was no imprint of magnetization of a later date, it is concluded that the Indian plate was located in the .... swarms, that occur in this craton. Thus the .... b, c and d, needed to explain the anomalies along with the ...

  18. Palaeomagnetism of the Palaeoproterozoic Boonadgin Dyke Suite, Yilgarn Craton: Possible connection with India

    Science.gov (United States)

    Liu, Y.; Li, Z. X.; Pisarevsky, S.; Kirscher, U.; Mitchell, R.; Stark, J. C.

    2017-12-01

    A palaeomagnetic study was carried out on the newly identified 1.9 Ga Boonadgin dyke swarm in the Yilgarn Craton, Western Australia. Ten dykes revealed a high-temperature characteristic remanent magnetisation (ChRM) with dual polarities, directing either SW shallow downward (4 sites) or NE shallow upward (6 sites). Our results reveal that the Yilgarn Craton was at an equatorial palaeolatitude at 1.9 Ga. Meanwhile, a paleopole from the ca. 1.9 Ga Dharwar dykes of South India, supported by a positive baked-contact test, puts India at a similar paleolatitude. The Boonadgin dyke swarm can be interpreted to represent an arm of a radiating dyke swarm that shared the same plume centre with coeval mafic dykes in the Dharwar and Bastar cratons of southern India. We therefore propose that the Western Australia Craton (WAC, consisting of the the Yilgarn and Pilbara cratons) and South India were connected at ca. 1.89 Ga.

  19. Heat flow, heat generation and crustal thermal structure of the northern block of the South Indian Craton

    Science.gov (United States)

    Gupta, Mohan L.; Sharma, S. R.; Sundar, A.

    Heat flow values and heat generation data calculated from the concentration of heat producing radioactive elements, U, Th and K in surface rocks were analyzed. The South Indian Craton according to Drury et al., can be divided into various blocks, separated by late Proterozoic shear belts. The northern block comprises Eastern and Western Dharwar Cratons of Rogers (1986), Naqvi and Rogers (1987) and a part of the South Indian granulite terrain up to a shear system occupying the Palghat-Cauvery low lands. The geothermal data analysis clearly demonstrates that the present thermal characteristics of the above two Archaean terrains of the Indian and Australian Shields are quite similar. Their crustal thermal structures are likely to be similar also.

  20. Heat flow, heat generation and crustal thermal structure of the northern block of the South Indian Craton

    Science.gov (United States)

    Gupta, Mohan L.; Sharma, S. R.; Sundar, A.

    1988-01-01

    Heat flow values and heat generation data calculated from the concentration of heat producing radioactive elements, U, Th and K in surface rocks were analyzed. The South Indian Craton according to Drury et al., can be divided into various blocks, separated by late Proterozoic shear belts. The northern block comprises Eastern and Western Dharwar Cratons of Rogers (1986), Naqvi and Rogers (1987) and a part of the South Indian granulite terrain up to a shear system occupying the Palghat-Cauvery low lands. The geothermal data analysis clearly demonstrates that the present thermal characteristics of the above two Archaean terrains of the Indian and Australian Shields are quite similar. Their crustal thermal structures are likely to be similar also.

  1. Implications of new ^{40}Ar/^{39}Ar age of Mallapur Intrusives on the chronology and evolution of the Kaladgi Basin, Dharwar Craton, India

    Science.gov (United States)

    Pillai, Shilpa Patil; Pande, Kanchan; Kale, Vivek S.

    2018-04-01

    The Kaladgi Basin on the northern edge of the Dharwar craton has characters diverse from the other epicratonic Purana basins of Peninsular India. Sedimentological studies in the basin have established the presence of three cycles of flooding separated by an event of intra-basinal deformation accompanied by low grade incipient metamorphism. The overall structural configuration of the basin indicates its development by supracrustal extension accompanied by shearing in a trans-tensional regime during the Mesoproterozoic. This was followed by sagging that yielded Neoproterozoic sedimentation in a successor nested basin. ^{40}Ar/^{39}Ar dating of an intrusive mafic dyke along the axial plane of a fold has yielded a plateau age of 1154{± }4 Ma. This helps constraint the age of the various events during the evolution of this basin.

  2. U-Pb and Lu-Hf systematics of zircons from Sargur metasediments, Dharwar Craton, Southern India: new insights on the provenance and crustal evolution

    International Nuclear Information System (INIS)

    Maibam, Bidyananda; Gerdes, Axel; Srinivasan, R.; Goswami, J.N.

    2017-01-01

    A study of U-Pb and Lu-Hf-Yb isotope data in zircons from metamorphosed psammopelite and quartzite from the type area of Archaean Sargur Group, Dharwar Craton, India is carried out. Two age populations are observed: an older population with concordant U-Pb ages between 2.7 and 2.8 Ga, and a younger population with ages in the 2.4 - 2.6 Ga age range. The εHf values of 0 to + 2.0 for the older zircon population suggest that they were derived from juvenile crust formed at 2.7- 2.8 Ga. Sub-chondritic εHf values for the younger population indicate metamorphism and/or crustal reworking at ∼2.5 Ga. Meta-sedimentary enclaves in the Sargur type area are therefore part of the gneiss-supracrustal complex of different antiquities and may not have an independent stratigraphic status. (author)

  3. A geological synthesis of the Precambrian shield in Madagascar

    Science.gov (United States)

    Tucker, Robert D.; Roig, J.Y.; Moine, B.; Delor, C.; Peters, S.G.

    2014-01-01

    Available U–Pb geochronology of the Precambrian shield of Madagascar is summarized and integrated into a synthesis of the region’s geological history. The shield is described in terms of six geodynamic domains, from northeast to southwest, the Bemarivo, Antongil–Masora, Antananarivo, Ikalamavony, Androyan–Anosyan, and Vohibory domains. Each domain is defined by distinctive suites of metaigneous rocks and metasedimentary groups, and a unique history of Archean (∼2.5 Ga) and Proterozoic (∼1.0 Ga, ∼0.80 Ga, and ∼0.55 Ga) reworking. Superimposed within and across these domains are scores of Neoproterozoic granitic stocks and batholiths as well as kilometer long zones of steeply dipping, highly strained rocks that record the effects of Gondwana’s amalgamation and shortening in latest Neoproterozoic time (0.560–0.520 Ga). The present-day shield of Madagascar is best viewed as part of the Greater Dharwar Craton, of Archean age, to which three exotic terranes were added in Proterozoic time. The domains in Madagascar representing the Greater Dharwar Craton include the Antongil–Masora domain, a fragment of the Western Dharwar of India, and the Neoarchean Antananarivo domain (with its Tsaratanana Complex) which is broadly analogous to the Eastern Dharwar of India. In its reconstructed position, the Greater Dharwar Craton consists of a central nucleus of Paleo-Mesoarchean age (>3.1 Ga), the combined Western Dharwar and Antongil–Masora domain, flanked by mostly juvenile “granite–greenstone belts” of Neoarchean age (2.70–2.56 Ga). The age of the accretionary event that formed this craton is approximately 2.5–2.45 Ga. The three domains in Madagascar exotic to the Greater Dharwar Craton are the Androyan–Anosyan, Vohibory, and Bemarivo. The basement to the Androyan–Anosyan domain is a continental terrane of Paleoproterozoic age (2.0–1.78 Ga) that was accreted to the southern margin (present-day direction) of the Greater Dharwar Craton in pre

  4. Proterozoic orogenic belts and rifting of Indian cratons: Geophysical constraints

    Directory of Open Access Journals (Sweden)

    D.C. Mishra

    2014-01-01

    Full Text Available The Aravalli–Delhi and Satpura Mobile Belts (ADMB and SMB and the Eastern Ghat Mobile Belt (EGMB in India form major Proterozoic mobile belts with adjoining cratons and contemporary basins. The most convincing features of the ADMB and the SMB have been the crustal layers dipping from both sides in opposite directions, crustal thickening (∼45 km and high density and high conductivity rocks in upper/lower crust associated with faults/thrusts. These observations indicate convergence while domal type reflectors in the lower crust suggest an extensional rifting phase. In case of the SMB, even the remnant of the subducting slab characterized by high conductive and low density slab in lithospheric mantle up to ∼120 km across the Purna–Godavari river faults has been traced which may be caused by fluids due to metamorphism. Subduction related intrusives of the SMB south of it and the ADMB west of it suggest N–S and E–W directed convergence and subduction during Meso–Neoproterozoic convergence. The simultaneous E–W convergence between the Bundelkhand craton and Marwar craton (Western Rajasthan across the ADMB and the N–S convergence between the Bundelkhand craton and the Bhandara and Dharwar cratons across the SMB suggest that the forces of convergence might have been in a NE–SW direction with E–W and N–S components in the two cases, respectively. This explains the arcuate shaped collision zone of the ADMB and the SMB which are connected in their western part. The Eastern Ghat Mobile Belt (EGMB also shows signatures of E–W directed Meso–Neoproterozoic convergence with East Antarctica similar to ADMB in north India. Foreland basins such as Vindhyan (ADMB–SMB, and Kurnool (EGMB Supergroups of rocks were formed during this convergence. Older rocks such as Aravalli (ADMB, Mahakoshal–Bijawar (SMB, and Cuddapah (EGMB Supergroups of rocks with several basic/ultrabasic intrusives along these mobile belts, plausibly formed during

  5. Fluid inclusion, geochemical, Rb–Sr and Sm–Nd isotope studies on ...

    Indian Academy of Sciences (India)

    Sundarrajan Vijay Anand

    2018-05-22

    May 22, 2018 ... J. Earth Syst. Sci. (2018) 127:52 c Indian ..... performed using thermal ionization mass spectrom- eter (model-Triton ..... The molecular proportion of ..... belt, Eastern Dharwar craton: Constraints on age, dura- tion of volcanism ...

  6. Petrogenesis of the crater-facies Tokapal kimberlite pipe, Indrāvati Basin, Central India

    Directory of Open Access Journals (Sweden)

    N.V. Chalapathi Rao

    2014-11-01

    Full Text Available New geochemical data of the crater-facies Tokapal kimberlite system sandwiched between the lower and upper stratigraphic horizons of the Mesoproterozoic Indrāvati Basin are presented. The kimberlite has been subjected to extensive and pervasive low-temperature alteration. Spinel is the only primary phase identifiable, while olivine macrocrysts and juvenile lapilli are largely pseudomorphed (talc-serpentine-carbonate alteration. However, with the exception of the alkalies, major element oxides display systematic fractionation trends; likewise, HFSE patterns are well correlated and allow petrogenetic interpretation. Various crustal contamination indices such as (SiO2 + Al2O3 + Na2O/(MgO + K2O and Si/Mg are close to those of uncontaminated kimberlites. Similar La/Yb (79–109 of the Tokapal samples with those from the kimberlites of Wajrakarur (73–145 and Narayanpet (72–156, Eastern Dharwar craton, southern India implies a similarity in their genesis. In the discriminant plots involving HFSE the Tokapal samples display strong affinities to Group II kimberlites from southern Africa and central India as well as to ‘transitional kimberlites’ from the Eastern Dharwar craton, southern India, and those from the Prieska and Kuruman provinces of southern Africa. There is a striking similarity in the depleted-mantle (TDM Nd model ages of the Tokapal kimberlite system, Bastar craton, the kimberlites from NKF and WKF, Eastern Dharwar craton, and the Majhgawan diatreme, Bundelkhand craton, with the emplacement age of some of the lamproites from within and around the Palaeo-Mesoproterozoic Cuddapah basin, southern India. These similar ages imply a major tectonomagmatic event, possibly related to the break-up of the supercontinent of Columbia, at 1.3–1.5 Ga across the three cratons. The ‘transitional’ geochemical features displayed by many of the Mesoproterozoic potassic-ultrapotassic rocks, across these Indian cratons are inferred to be

  7. Pb–Pb zircon ages of Archaean metasediments and gneisses from ...

    Indian Academy of Sciences (India)

    eastern parts of the Dharwar craton took place over similar time interval starting in the Mesoarchaean at ca. .... the age of the Bababudan Group between 2.91 and. 2.72 Ga. ..... All the samples were processed using a standard technique to ...

  8. SUBJECT INDEX

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    granulite belt, India: structural and petrochemical evidences attesting to their relict nature. 337. Earth systems. Earth support systems: Threatened? Why? What can we do? 269. Earthquake source. Earthquake source model using strong motion dis- placement as response of finite elastic media. 9. Eastern Dharwar Craton.

  9. Sediment-infill volcanic breccia from the Neoarchean Shimoga greenstone terrane, western Dharwar Craton: Implications on pyroclastic volcanism and sedimentation in an active continental margin

    Science.gov (United States)

    Manikyamba, C.; Saha, Abhishek; Ganguly, Sohini; Santosh, M.; Lingadevaru, M.; Rajanikanta Singh, M.; Subba Rao, D. V.

    2014-12-01

    We report sediment-infill volcanic breccia from the Neoarchean Shimoga greenstone belt of western Dharwar Craton which is associated with rhyolites, chlorite schists and pyroclastic rocks. The pyroclastic rocks of Yalavadahalli area of Shimoga greenstone belt host volcanogenic Pb-Cu-Zn mineralization. The sediment-infill volcanic breccia is clast-supported and comprises angular to sub-angular felsic volcanic clasts embedded in a dolomitic matrix that infilled the spaces in between the framework of volcanic clasts. The volcanic clasts are essentially composed of alkali feldspar and quartz with accessory biotite and opaques. These clasts have geochemical characteristics consistent with that of the associated potassic rhyolites from Daginkatte Formation. The rare earth elements (REE) and high field strength element (HFSE) compositions of the sediment-infill volcanic breccia and associated mafic and felsic volcanic rocks suggest an active continental margin setting for their generation. Origin, transport and deposition of these rhyolitic clasts and their aggregation with infiltrated carbonate sediments may be attributed to pyroclastic volcanism, short distance transportation of felsic volcanic clasts and their deposition in a shallow marine shelf in an active continental margin tectonic setting where the rhyolitic clasts were cemented by carbonate material. This unique rock type, marked by close association of pyroclastic volcanic rocks and shallow marine shelf sediments, suggest shorter distance between the ridge and shelf in the Neoarchean plate tectonic scenario.

  10. Journal of Earth System Science | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Google Earth Image and cross-cutting field relationships of distinct Paleoproterozoic mafic dykes from south of Devarakonda area in the Eastern Dharwar Craton has been studied to establish relative emplacement ages. The Devarakonda, covering an area of ∼700 km2, shows spectacular cross-cutting field relationships ...

  11. Correlations between the North China Craton and the Indian Shield: Constraints from regional metallogeny

    Directory of Open Access Journals (Sweden)

    Caifeng Li

    2015-11-01

    Full Text Available The correlation between the North China Craton (NCC and the Indian Shield (IND has been a hot topic in recent years. On the basis of ore deposit databases, the NCC and IND have shown broad similarity in metallogenesis from the middle Archaean to the Mesoproterozoic. The two blocks both have three major metallogenic systems: (1 the Archaean BIF metallogenic system; (2 the Paleoproterozoic Cu-Pb-Zn metallogenic system; and (3 the Mesoproterozoic Fe-Pb-Zn system. In the north margin of the NCC and the west margin of the IND, the Archaean BIF-Au-Cu-Pb-Zn deposits had the same petrogenesis and host rocks, the Paleoproterozoic Cu-Pb-Zn deposits were controlled by active belts, and the Mesoproterozoic Fe-Pb-Zn deposits were mainly related to multi-stage rifting. Matching regional mineralization patterns and geological features has established the continental assembly referred to as “NCWI”, an acronym for the north margin of the NCC (NC and the west margin of the IND (WI during the middle Archaean to the Mesoproterozoic. In this assembly, the available geological and metallogenic data from the Eastern Block and active belts of NC fit those from the Dharwar craton and the Aravalli–Delhi–Vindhyan belt of WI, respectively. Moreover, the depositional model and environment of Paleoproterozoic metasedimentary manganese deposits in NCWI implied that the assembly may be located at low latitudes, where the conditions were favorable for dissolving ice and precipitating manganese deposits.

  12. A geochemical and Pb, Sr isotopic study of the evolution of granite-gneisses from the Bastar craton, Central India

    International Nuclear Information System (INIS)

    Sarkar, G.; Paul, D.K.; Misra, V.P.; de Laeter, J.R.; Mc Naughton, N.J.

    1990-01-01

    Preliminary Pb-Pb and Rb-Sr geochronology of granitic and gneissic rocks from the Sukma area of the Bastar craton, Central India, provides important constraints on crustal evolution. Much of the craton is made up of felsic orthogneisses and younger granitic intrusives, compositionally ranging from tonalite to granite. Pb-Pb isotopic data suggest the presence of ca. 3.0 Ga old gneisses. Younger granitic intrusives have been dated at ca. 2.6 Ga which represents a widespread resetting and/or emplacement event. Comparison of the Pb-Pb and Rb-Sr whole rock ages suggests that the latter were more perturbed after the gneiss-forming or emplacement events. All rock suites show significant geological scatter of isotopic data probably because of sampling on a regional scale, and reflect multi-stage isotopic evolution in a complex terrain. The present isotopic data indicate the presence of Archaean rock in the Bastar craton and suggest temporal similarity with the oldest crustal rocks in the Singhbhum and Dharwar cratons. (author). 18 refs., 4 tabs., 8 figs

  13. Gravity and magnetic modelling in the Vrancea Zone, south-eastern Carpathians: Redefinition of the edge of the East European Craton beneath the south-eastern Carpathians

    Science.gov (United States)

    Bocin, A.; Stephenson, R.; Matenco, L.; Mocanu, V.

    2013-11-01

    A 2D gravity and magnetic data model has been constructed along a 71 km densely observed profile, called DACIA PLAN GRAV MAN's. The profile crosses part of the nappe pile of the south-eastern Carpathians and includes the seismically active Vrancea Zone and was acquired with the objective to illuminate the basement structure and affinity in this area. The modelling approach was to create an initial model from well constrained geological information, integrate it with previous seismic ray tracing and tomographic models and then alter it outside the a priori constraints in order to reach the best fit between observed and calculated potential field anomalies. The results support a realignment of the position of the TTZ (Tornquist-Teisseyre Zone), the profound tectonic boundary within Europe that separates Precambrian cratonic lithosphere of the East European Craton (EEC) from younger accreted lithosphere of Phanerozoic mobile belts to its west. The TTZ is shown to lie further to the south-west than was previously inferred within Romania, where it is largely obscured by the Carpathian nappes. The crust of the EEC beneath the south-eastern Carpathians is inferred to terminate along a major crustal structure lying just west of the Vrancea seismogenic zone. The intermediate depth seismicity of the Vrancea Zone therefore lies within the EEC lithosphere, generally supporting previously proposed models invoking delamination of cratonic lithosphere as the responsible mechanism.

  14. Petrogenesis of 3.15 Ga old Banasandra komatiites from the Dharwar craton, India: Implications for early mantle heterogeneity

    Directory of Open Access Journals (Sweden)

    J.M. Maya

    2017-05-01

    Full Text Available Spinifex-textured, magnesian (MgO >25 wt.% komatiites from Mesoarchean Banasandra greenstone belt of the Sargur Group in the Dharwar craton, India were analysed for major and trace elements and 147,146Sm-143,142Nd systematics to constrain age, petrogenesis and to understand the evolution of Archean mantle. Major and trace element ratios such as CaO/Al2O3, Al2O3/TiO2, Gd/Yb, La/Nb and Nb/Y suggest aluminium undepleted to enriched compositional range for these komatiites. The depth of melting is estimated to be varying from 120 to 240 km and trace-element modelling indicates that the mantle source would have undergone multiple episodes of melting prior to the generation of magmas parental to these komatiites. Ten samples of these komatiites together with the published results of four samples from the same belt yield 147Sm-143Nd isochron age of ca. 3.14 Ga with an initial ɛNd(t value of +3.5. High precision measurements of 142Nd/144Nd ratios were carried out for six komatiite samples along with standards AMES and La Jolla. All results are within uncertainties of the terrestrial samples. The absence of 142Nd/144Nd anomaly indicates that the source of these komatiites formed after the extinction of 146Sm, i.e. 4.3 Ga ago. In order to evolve to the high ɛNd(t value of +3.5 by 3.14 Ga the time-integrated ratio of 147Sm/144Nd should be 0.2178 at the minimum. This is higher than the ratios estimated, so far, for mantle during that time. These results indicate at least two events of mantle differentiation starting with the chondritic composition of the mantle. The first event occurred very early at ∼4.53 Ga to create a global early depleted reservoir with superchondritic Sm/Nd ratio. The source of Isua greenstone rocks with positive 142Nd anomaly was depleted during a second differentiation within the life time of 146Sm, i.e. prior to 4.46 Ga. The source mantle of the Banasandra komatiite was a result of a differentiation event that occurred

  15. The 3.1 Ga Nuggihalli chromite deposits, Western Dhawar craton (India)

    DEFF Research Database (Denmark)

    Mukherjee, Ria; Mondal, Sisir K.; Frei, Robert

    2012-01-01

    The Nuggihalli greenstone belt is part of the older greenstone belts (3.4 - 3.0 Ga) in the Western Dharwar Craton, southern India. This greenstone sequence consists of conformable metavolcanic and metasedimentary supracrustal rock assemblages that belong to the Sargur Group. Sill-like ultramafic......-mafic plutonic bodies are present within these supracrustal rocks (schist rocks) which are in turn enclosed by tonalite-trondhjemite-granodiorite gneiss (TTG). The sill-like ultramafic-mafic rocks are cumulates derived from a high-Mg parental magma that are represented by chromitite-hosted serpentinite...... and tremolite-chlorite-actinolite- schist (altered peridotite), anorthosite, pyroxenite, and gabbro hosting magnetite bands. The first whole-rock Sm-Nd data for the peridotite anorthosite- pyroxenite-gabbro unit has been obtained yielding an age of 3125 ± 120 Ma (MSWD = 1.3) which is similar to reported ages...

  16. Studies on Archaean Dharwar Tectonic Province 433

    Indian Academy of Sciences (India)

    age data on the geological evolution of southern India; Proc. workshop on deep continental crust of. South India, LPI Tech. Tept. No. 88-06, pp. 181-183. Viswanatha M. N, Ramakrishnan M and Swami Nath J 1982 Angular unconformity between Sargur and. Dharwar supracrustals in Shigegudda, Karnataka cration, South ...

  17. 3D Crustal Velocity Structure Model of the Middle-eastern North China Craton

    Science.gov (United States)

    Duan, Y.; Wang, F.; Lin, J.; Wei, Y.

    2017-12-01

    Lithosphere thinning and destruction in the middle-eastern North China Craton (NCC), a region susceptible to strong earthquakes, is one of the research hotspots in solid earth science. Up to 42 wide-angle reflection/refraction deep seismic sounding (DSS) profiles have been completed in the middle-eastern NCC, we collect all the 2D profiling results and perform gridding of the velocity and interface depth data, and build a 3D crustal velocity structure model for the middle-eastern NCC, named HBCrust1.0, using the Kriging interpolation method. In this model, four layers are divided by three interfaces: G is the interface between the sedimentary cover and crystalline crust, with velocities of 5.0-5.5 km/s above and 5.8-6.0 km/s below. C is the interface of the upper and lower crust, with velocity jump from 6.2-6.4 km/s to 6.5-6.6 km/s. M is the interface between the crust and upper mantle, with velocity 6.7-7.0 km/s at the crust bottom and 7.9-8.0 km/s on mantle top. Our results show that the first arrival time calculated from HBCust1.0 fit well with the observation. It also demonstrates that the upper crust is the main seismogenic layer, and the brittle-ductile transition occurs at depths near interface C. The depth of interface Moho varies beneath the source area of the Tangshan earth-quake, and a low-velocity structure is found to extend from the source area to the lower crust. Based on these observations, it can be inferred that stress accumulation responsible for the Tangshan earthquake may have been closely related to the migration and deformation of the mantle materials. Comparisons of the average velocities of the whole crust, the upper and the lower crust show that the average velocity of the lower crust under the central part of the North China Basin (NCB) in the east of the craton is obviously higher than the regional average, this high-velocity probably results from longterm underplating of the mantle magma. This research is founded by the Natural Science

  18. Journal of Earth System Science | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    New paleomagnetic results on ~2367 Ma Dharwar giant dyke swarm, Dharwar craton, southern India: implications for Paleoproterozoic continental reconstruction · N Ramesh Babu M Venkateshwarlu Ravi Shankar E Nagaraju V Parashuramulu · More Details Abstract Fulltext PDF. Here we report new paleomagnetic results ...

  19. Extensive crustal melting during craton destruction: Evidence from the Mesozoic magmatic suite of Junan, eastern North China Craton

    Science.gov (United States)

    Yang, Fan; Santosh, M.; Tang, Li

    2018-05-01

    The cratonic destruction associated with the Pacific plate subduction beneath the eastern North China Craton (NCC) shows a close relationship with the widespread magmatism during the Late Mesozoic. Here we investigate a suite of intrusive and extrusive magmatic rocks from the Junan region of the eastern NCC in order to evaluate the role of extensive crustal melting related to decratonization. We present petrological, geochemical, zircon U-Pb geochronological and Lu-Hf isotopic data to evaluate the petrogenesis, timing and tectonic significance of the Early Cretaceous magmatism. Zircon grains in the basalt from the extrusive suite of Junan show multiple populations with Neoproterozoic and Early Paleozoic xenocrystic grains ranging in age from 764 Ma to 495 Ma as well as Jurassic grains with an age range of 189-165 Ma. The dominant population of magmatic zircon grains in the syenite defines three major age peaks of 772 Ma, 132 Ma and 126 Ma. Zircons in the granitoids including alkali syenite, monzonite and granodiorite yield a tightly restricted age range of 124-130 Ma representing their emplacement ages. The Neoproterozoic (841-547 Ma) zircon grains from the basalt and the syenite possess εHf(t) values of -22.9 to -8.4 and from -18.8 to -17.3, respectively. The Early Paleozoic (523-494 Ma) zircons from the basalt and the syenite also show markedly negative εHf(t) values of -22.7 to -18.0. The dominant population of Early Cretaceous (134-121 Ma) zircon grains presented in all the samples also displays negative εHf(t) values range from -31.7 to -21.1, with TDM of 1653-2017 Ma and TDMC in the range of 2193-3187 Ma. Accordingly, the Lu-Hf data suggest that the parent magma was sourced through melting of Mesoarchean to Paleoproterozoic basement rocks. Geochemical data on the Junan magmatic suite display features similar to those associated with the arc magmatic rocks involving subduction-related components, with interaction of fluids and melts in the suprasubduction

  20. Contrasted continental rifting via plume-craton interaction: Applications to Central East African Rift

    Directory of Open Access Journals (Sweden)

    Alexander Koptev

    2016-03-01

    Full Text Available The East African Rift system (EARS provides a unique system with the juxtaposition of two contrasting yet simultaneously formed rift branches, the eastern, magma-rich, and the western, magma-poor, on either sides of the old thick Tanzanian craton embedded in a younger lithosphere. Data on the pre-rift, syn-rift and post-rift far-field volcanic and tectonic activity show that the EARS formed in the context of the interaction between a deep mantle plume and a horizontally and vertically heterogeneous lithosphere under far-field tectonic extension. We bring quantitative insights into this evolution by implementing high-resolution 3D thermo-mechanical numerical deformation models of a lithosphere of realistic rheology. The models focus on the central part of the EARS. We explore scenarios of plume-lithosphere interaction with plumes of various size and initial position rising beneath a tectonically pre-stretched lithosphere. We test the impact of the inherited rheological discontinuities (suture zones along the craton borders, of the rheological structure, of lithosphere plate thickness variations, and of physical and mechanical contrasts between the craton and the embedding lithosphere. Our experiments indicate that the ascending plume material is deflected by the cratonic keel and preferentially channeled along one of its sides, leading to the formation of a large rift zone along the eastern side of the craton, with significant magmatic activity and substantial melt amount derived from the mantle plume material. We show that the observed asymmetry of the central EARS, with coeval amagmatic (western and magmatic (eastern branches, can be explained by the splitting of warm material rising from a broad plume head whose initial position is slightly shifted to the eastern side of the craton. In that case, neither a mechanical weakness of the contact between the craton and the embedding lithosphere nor the presence of second plume are required to

  1. Reassessment of the geologic evolution of selected precambrian terranes in Brazil, based on new SHRIMP U-Pb data, part 1: central-eastern border of Sao Francisco Craton in Bahia state, Brazil

    International Nuclear Information System (INIS)

    Silva, Luiz Carlos da; Pimentel, Marcio; Jost, Hardy; Armstrong, Richard

    2002-01-01

    This paper discusses new U-Pb SHRIMP zircon data for 12 key-exposures of several geological units exposed at the eastern border of the Sao Francisco Craton. The samples represent mostly Archean basement units within the Paleoproterozoic Eastern Bahia Belt (Orogen). Samples were collected along several E-W tran sects trying to more accurately assess the areal distribution of the Archean polycyclic basement of the Sao Francisco Craton and to identify the limits of Paleoproterozoic metamorphic overprint resulting from the development of the Eastern Bahia Orogen. Owing to the polycyclic evolution and/or high grade metamorphic conditions which most of the rock units investigated have undergone, zircon morphology and the U-Pb analytical data exhibit very complex patterns. These are characterized by a combination of inheritance, partial resetting and new zircon growth during high grade metamorphism. As a consequence, very careful and detailed analyses of cathodoluminescence imagery were required to allow distinction between inheritance, newly melt-precipitated zircon and partially reset zircons, as well as between the ages of magmatic and metamorphic events. Except for one unit (sample LH 44), which present crystallization age of ca 3000 Ma - interpreted, therefore, as the eastern extension of the Serrinha Craton - the others are ascribed to two major age groups at ca. 2870-2500 Ma and ca. 2200?-2030 Ma. The former group includes ortho gneisses with crystallization ages between ca. 2870-2500 Ma, which have been mapped and interpreted, in its major extension, as juvenile Paleoproterozoic arc (Itabuna and Salvador-Curaca belts/domains). The new data presented in this study, however, indicate that these ortho gneisses represent a multi-episodic collage of primitive Archean orogenic arcs, which gave rise to the Archean basement of that part of the Sao Francisco Craton. All the investigated zircon populations were extensively recrystallized at ca. 2080-2050 Ma as a result of

  2. Le craton ouest-africain et le bouclier guyanais: un seul craton au Protérozoïque inférieur?

    Science.gov (United States)

    Caen-Vachette, Michelle

    Geochronological and paleomagnetism data for southern West African craton and Guyana shield in South America, are concordant and suggest the existence of a large unit grouping them during Archean and Lower Proterozoic times. The paleomagnetism data allow to put on a single line, the Zednes (Mauritania), Sassandra (Ivory Coast) and Guri (Venezuela) fault zones, the mylonites of which were dated 1670 Ma. This age reflects the end of the eburnean-transamazonian shearing tectonic, which affected the large West Africa-Guyana unit. This line separates the western Archean domain from the eastern lower Proterozoic one; thence it is possible to correlate the Sasca (Ivory Coast) and Pastora (Venezuela) areas. Archean relics have been found in mobile pan-african-bresiliano zones which surround the Precambrian cratons; this fact suggests the existence of still more extended Archean craton than defined above.

  3. Garnet pyroxenite from Nilgiri Block, southern India: Vestiges of a Neoarchean volcanic arc

    Science.gov (United States)

    Samuel, Vinod O.; Kwon, Sanghoon; Santosh, M.; Sajeev, K.

    2018-06-01

    Southern peninsular India preserves records of Late Neoarchean-Early Paleoproterozoic continental building and cratonization. A transect from the Paleoarchean Dharwar Craton to the Neoarchean arc magmatic complex in the Nilgiri Block across the intervening Moyar Suture Zone reveals an arc-accretionary complex composed of banded iron formation (BIF), amphibolite, metatuff, garnet-kyanite schist, metagabbro, pyroxenite and charnockite. Here we investigate the petrology, geochronology and petrogenesis of the pyroxenite and garnet-clinopyroxenite. The pyroxenite is mainly composed of orthopyroxene and clinopyroxene with local domains/pockets enriched in a clinopyroxene-garnet assemblage. Thermobarometric calculations and phase equilibria modeling suggest that the orthopyroxene- and clinopyroxene-rich domains formed at 900-1000 °C, 1-1.2 GPa whereas the garnet- and clinopyroxene-rich domains record higher pressure of about 1.8-2 GPa at similar temperature conditions (900-1000 °C). Zircon U-Pb SHRIMP dating show weighted mean 207Pb-206Pb age of 2532 ± 22 Ma, with metamorphic overgrowth at 2520 ± 27 Ma and 2478 ± 27 Ma. We propose a tectonic model involving decoupling and break-off of the oceanic plate along the southern flanks of the Dharwar Craton, which initiated oceanic plate subduction. Slab melting eventually built the Nilgiri volcanic arc on top of the over-riding plate along the flanks of the Dharwar Craton. Our study supports an active plate tectonic regime at the end of the Archean Era, aiding in the growth of paleo-continents and their assembly into stable cratons.

  4. 3D Numerical Model of Continental Breakup via Plume Lithosphere Interaction Near Cratonic Blocks: Implications for the Tanzanian Craton

    Science.gov (United States)

    Koptev, A.; Calais, E.; Burov, E. B.; Leroy, S. D.; Gerya, T.

    2014-12-01

    Although many continental rift basins and their successfully rifted counterparts at passive continental margins are magmatic, some are not. This dichotomy prompted end-member views of the mechanism driving continental rifting, deep-seated and mantle plume-driven for some, owing to shallow lithospheric stretching for others. In that regard, the East African Rift (EAR), the 3000 km-long divergent boundary between the Nubian and Somalian plates, provides a unique setting with the juxtaposition of the eastern, magma-rich, and western, magma-poor, branches on either sides of the 250-km thick Tanzanian craton. Here we implement high-resolution rheologically realistic 3D numerical model of plume-lithosphere interactions in extensional far-field settings to explain this contrasted behaviour in a unified framework starting from simple, symmetrical initial conditions with an isolated mantle plume rising beneath a craton in an east-west tensional far field stress. The upwelling mantle plume is deflected by the cratonic keel and preferentially channelled along one of its sides. This leads to the coeval development of a magma-rich branch above the plume head and a magma-poor one along the opposite side of the craton, the formation of a rotating microplate between the two rift branches, and the feeding of melt to both branches form a single mantle source. The model bears strong similarities with the evolution of the eastern and western branches of the central EAR and the geodetically observed rotation of the Victoria microplate. This result reconciles the passive (plume-activated) versus active (far-field tectonic stresses) rift models as our experiments shows both processes in action and demonstrate the possibility of developing both magmatic and amagmatic rifts in identical geotectonic environments.

  5. Implications of new age of Mallapur Intrusives on the chronology ...

    Indian Academy of Sciences (India)

    Shilpa Patil Pillai

    2018-03-27

    Mar 27, 2018 ... not have any geographic proximity with MPMB. The Purana basins display a paucity of asso- ciated contemporary igneous activity (Kale and. Phansalkar .... adjoining emergent cratonic segments of the. Dharwar craton. The younger Badami Group has a significant proportion of fluvial and fluvio-deltaic.

  6. Metasomatism and the Weakening of Cratons: A Mechanism to Rift Cratons

    Science.gov (United States)

    Wenker, Stefanie; Beaumont, Christopher

    2016-04-01

    The preservation of cratons is a demonstration of their strength and resistance to deformation. However, several cratons are rifting now (e.g. Tanzania and North China Craton) or have rifted in the past (e.g. North Atlantic Craton). To explain this paradox, we suggest that widespread metasomatism of the originally cold depleted dehydrated craton mantle lithosphere root can act as a potential weakening mechanism. This process, particularly melt metasomatism, increases root density through a melt-peridotite reaction, and reduces root viscosity by increasing the temperature and rehydrating the cratonic mantle lithosphere. Using 2D numerical models, we model silicate-melt metasomatism and rehydration of cold cratonic mantle lithosphere that is positioned beside standard Phanerozoic lithosphere. The models are designed to investigate when a craton is sufficiently weakened to undergo rifting and is no longer protected by the initially weaker adjacent standard Phanerozoic lithosphere. Melt is added to specified layers in the cratonic mantle lithosphere at a uniform volumetric rate determined by the duration of metasomatism (3 Myr, 10 Myr or 30 Myr), until a total of ~30% by volume of melt has been added. During melt addition heat and mass are properly conserved and the density and volume increase by the respective amounts required by the reaction with the peridotite. No extensional boundary conditions are applied to the models during the metasomatism process. As expected, significant refertilization leads to removal and thinning of progressively more gravitationally unstable cratonic mantle lithosphere. We show that the duration of metasomatism dictates the final temperature in the cratonic upper mantle lithosphere. Consequently, when extensional boundary conditions are applied in our rifting tests in most cases the Phanerozoic lithosphere rifts. The craton rifts only in the models with the hottest cratonic upper mantle lithosphere. Our results indicate rifting of cratons

  7. 2367 Ma Dharwar giant dyke swarm, Dharwar craton, southern India

    Indian Academy of Sciences (India)

    44

    Torsvik T H and Smethurst M A 1999 Plate Tectonic modeling: Virtual Reality with GMAP;. 406. Computer & Geosciences 25 395-402. 407. Valet J P, Besse J, Kumar A, Vadakke-Chanat S, and Philippe E 2014 The intensity of the. 408 geomagnetic field from 2.4 Ga old Indian dykes; Geochemis, Geophys, Geosys. 15 doi.

  8. Timing and implications for the late Mesozoic geodynamic settings of eastern North China Craton: Evidences from K-Ar dating age and sedimentary-structural characteristics records of Lingshan Island, Shandong Province

    Science.gov (United States)

    Li, Jie; Jin, Aiwen; Hou, Guiting

    2017-12-01

    The Lingshan Island in Shandong Province in the eastern North China Craton, well known for the Late Mesozoic multi-scale slide-slump structures is related to paleo-earthquake. Terrigenous clastic rocks, volcanic clastic rocks and volcanic lavas are extensively exposed in the Lingshan Island and its adjacent regions of the Shandong Province, which led to fierce debates on their ages, sedimentary characteristics and tectono-sedimentary evolution. In this contribution, we present the characteristics of the Late Mesozoic stratigraphy in the Lingshan Island. Whole-rock K-Ar dating of dyke at Beilaishi and rhyolites at Laohuzui of the Lingshan Island yielded ages of 159 Ma and 106-92 Ma which coincides with the Laiyang Period rifting and the Qingshan Period rifting in the Jiaolai Basin, respectively. On the basis of the analysis to the Late Mesozoic sedimentary environment of `flysch' and `molasse'-like formations as well as tectonic stress fields reconstruction, four episodes of the tectono-sedimentary evolution were established in the Lingshan Island and its adjacent regions in the eastern North China Craton. They consist of two episodes of extensional events for the syn-rift, and two episodes of compression events for the inversion of the post-rift. The entire episodes can be summarized as follows: (1) the first syn-rift NW-SE extension in Laiyang Period can be identified by the `flysch' formation (Unit 1) and by emplacement of the NE-trending dyke in the Laiyang Group. This syn-rift episode can be related to the NW-SE post-orogenic extension resulted from the gravity collapse of the thickened lithosphere along the Sulu Orogen. (2) The first post-rift NW-SE inversion, which was caused by the NW-directed subduction of Izanaqi Plate, can be well documented by the `X' type conjugate joints as well as slide slump folds in Unit 1. (3) The second syn-rift NW-SE extension in Qingshan Period is characterized by rhyolite rocks (Unit 2). This syn-rift episode can be considered

  9. Integrated elemental and Sr-Nd-Pb-Hf isotopic studies of Mesozoic mafic dykes from the eastern North China Craton: implications for the dramatic transformation of lithospheric mantle

    Science.gov (United States)

    Liu, Shen; Feng, Caixia; Santosh, M.; Feng, Guangying; Coulson, Ian M.; Xu, Mengjing; Guo, Zhuang; Guo, Xiaolei; Peng, Hao; Feng, Qiang

    2018-02-01

    Evolution of the lithospheric mantle beneath the North China Craton (NCC) from its Precambrian cratonic architecture until Paleozoic, and the transformation to an oceanic realm during Mesozoic, with implications on the destruction of cratonic root have attracted global attention. Here we present geochemical and isotopic data on a suite of newly identified Mesozoic mafic dyke swarms from the Longwangmiao, Weijiazhuang, Mengjiazhuang, Jiayou, Huangmi, and Xiahonghe areas (Qianhuai Block) along the eastern NCC with an attempt to gain further insights on the lithospheric evolution of the region. The Longwangmiao dykes are alkaline with LILE (Ba and K)- and LREE-enrichment ((La/Yb) N > 4.3) and EM1-like Sr-Nd-Pb-Hf isotopic signature ((87Sr/86Sr) i > 0.706; ε Nd (t) 16.6, (207Pb/204Pb) i > 15.4, (208Pb/204Pb) i > 36.8, ε Hf (t) 3.7), and display similar EM1-like isotopic features ((87Sr/86Sr) i > 0.706; ε Nd (t) 16.7, (207Pb/204Pb) i > 15.4, (208Pb/204Pb) i > 36.9, ε Hf (t) 2.4) and EM1-like isotopic features((87Sr/86Sr) i > 0.706; ε Nd (t) 16.7, (207Pb/204Pb) i > 15.4, (208Pb/204Pb) i > 36.9, ε Hf (t) 3.7) and EM1-like Sr-Nd-Pb-Hf isotopic features ((87Sr/86Sr) i > 0.706; ε Nd(t) 16.7, (207Pb/204Pb) i > 15.4, (208Pb/204Pb) i > 36.9, ε Hf (t) 9.3) and EM1-like isotopic composition ((87Sr/86Sr) i > 0.705; ε Nd (t) 16.9, (207Pb/204Pb) i > 15.5, (208Pb/204Pb) i > 36.9, ε Hf (t) 0.705; ε Nd (t) 16.9, (207Pb/204Pb) i > 15.5, (208Pb/204Pb) i > 36.9, ε Hf (t) < -8.6). Our data from the various mafic dyke suites suggest that the magmas were derived from EM1-like lithospheric mantle, corresponding to lithospheric mantle modified by the previously foundered lower crust beneath the eastern NCC. Our results suggest contrasting lithospheric evolution from Triassic (212 Ma) to Cretaceous (123 Ma) beneath the NCC. These mafic dykes mark an important phase of lithospheric thinning in the eastern North China Craton.

  10. Rifting an Archaean Craton: Insights from Seismic Anisotropy Patterns in E. Africa

    Science.gov (United States)

    Ebinger, C. J.; Tiberi, C.; Currie, C. A.; van Wijk, J.; Albaric, J.

    2016-12-01

    Few places worldwide offer opportunities to study active deformation of deeply-keeled cratonic lithosphere. The magma-rich Eastern rift transects the eastern edge of the Archaean Tanzania craton in northeastern Tanzania, which has been affected by a large-scale mantle upwelling. Abundant xenolith locales offer constraints on mantle age, composition, and physical properties. Our aim is to evaluate models for magmatic fluid-alteration (metasomatism) and deformation of mantle lithosphere along the edge of cratons by considering spatial variations in the direction and magnitude of seismic anisotropy, which is strongly influenced by mantle flow patterns along lithosphere-asthenosphere topography, fluid-filled cracks (e.g., dikes), and pre-existing mantle lithosphere strain fabrics. Waveforms of teleseismic earthquakes (SKS, SKKS) recorded on the 39-station CRAFTI-CoLiBREA broadband array in southern Kenya and northern Tanzania are used to determine the azimuth and amount of shear-wave splitting accrued as seismic waves pass through the uppermost mantle and lithosphere at the craton edge. Lower crustal earthquakes enable evaluation of seismic anisotropy throughout the crust along the rift flanks and beneath the heavily intruded Magadi and Natron basins, and the weakly intruded Manyara basin. Our results and those of earlier studies show a consistent N50E splitting direction within the craton, with delay times of ca. 1.5 s, and similar direction east of the rift in thinner Pan-African lithosphere. Stations within the rift zone are rotated to a N15-35E splitting, with the largest delay times of 2.5 s at the margin of the heavily intruded Magadi basin. The short length scale of variations and rift-parallel splitting directions are similar to patterns in the Main Ethiopian rift attributed to melt-filled cracks or oriented pockets rising from the base of the lithosphere. The widespread evidence for mantle metasomatism and magma intrusion to mid-crustal levels suggests that

  11. Lithospheric structure of southern Indian shield and adjoining oceans: integrated modelling of topography, gravity, geoid and heat flow data

    Science.gov (United States)

    Kumar, Niraj; Zeyen, H.; Singh, A. P.; Singh, B.

    2013-07-01

    For the present 2-D lithospheric density modelling, we selected three geotransects of more than 1000 km in length each crossing the southern Indian shield, south of 16°N, in N-S and E-W directions. The model is based on the assumption of local isostatic equilibrium and is constrained by the topography, gravity and geoid anomalies, by geothermal data, and where available by seismic data. Our integrated modelling approach reveals a crustal configuration with the Moho depth varying from ˜40 km beneath the Dharwar Craton, and ˜39 km beneath the Southern Granulite Terrane to about 15-20 km beneath the adjoining oceans. The lithospheric thickness varies significantly along the three profiles from ˜70-100 km under the adjoining oceans to ˜130-135 km under the southern block of Southern Granulite Terrane including Sri Lanka and increasing gradually to ˜165-180 km beneath the northern block of Southern Granulite Terrane and the Dharwar Craton. This step-like lithosphere-asthenosphere boundary (LAB) structure indicates a normal lithospheric thickness beneath the adjoining oceans, the northern block of Southern Granulite Terrane and the Dharwar Craton. The thin lithosphere below the southern block of Southern Granulite Terrane including Sri Lanka is, however, atypical considering its age. Our results suggest that the southern Indian shield as a whole cannot be supported isostatically only by thickened crust; a thin and hot lithosphere beneath the southern block of Southern Granulite Terrane including Sri Lanka is required to explain the high topography, gravity, geoid and crustal temperatures. The widespread thermal perturbation during Pan-African (550 Ma) metamorphism and the breakup of Gondwana during late Cretaceous are proposed as twin cause mechanism for the stretching and/or convective removal of the lower part of lithospheric mantle and its replacement by hotter and lighter asthenosphere in the southern block of Southern Granulite Terrane including Sri Lanka

  12. Structural appraisal of the Gadag schist belt from gravity investigations

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    From qualitative analysis of the gravity data, several tectonic features are ... major types of schist belts are identified in the ... Dharwar craton; Gadag schist belt; gravity method; inversion. ..... the Research Associateship of Dr D Himabindu.

  13. The Chara-Sina dyke swarm in the structure of the Middle Paleozoic Vilyui rift system (Siberian Craton)

    Science.gov (United States)

    Kiselev, A. I.; Konstantinov, K. M.; Yarmolyuk, V. V.; Ivanov, A. V.

    2016-11-01

    The formation of the Vilyui rift system in the eastern Siberian Craton was finished with breakdown of the continent and formation of its eastern margin. A characteristic feature of this rift system is the radial distribution of dyke swarms of basic rocks. This peculiarity allows us to relate it to the breaking processes above the mantle plume, the center of which was located in the region overlain in the modern structure by the foreland of the Verkhoyan folded-thrust belt. The Chara-Sina dyke swarm is the southern part of a large area of Middle Paleozoic basaltic magmatism in the eastern Siberian Craton. The OIB-like geochemical characteristics of dolerite allow us to suggest that the melting substrate for Middle Paleozoic basaltic magmatism was represented by a relatively homogeneous, mid-depleted mantle of the plume with geochemical parameters similar to those of OIB.

  14. Precambrian mega lineaments across the Indian sub-continent - Preliminary evidence from offshore magnetic data

    Digital Repository Service at National Institute of Oceanography (India)

    Subrahmanyam, V.; Subrahmanyam, A.S.; Murthy, K.S.R.; Murty, G.P.S.; Sarma, K.V.L.N.S.; SuneetaRani, P.; Anuradha, A.

    junction/contact between two major geological provinces, viz. the Southern Granulite Terrain (SGT) and the Dharwar Craton. In addition to these two mega lineaments, major faults have been inferred, which acted as controlling parameters to create a bulge...

  15. Contrasted continental rifting via plume-craton interaction : Applications to Central East African Rift

    NARCIS (Netherlands)

    Koptev, Alexander; Burov, Evgueni; Calais, Eric; Leroy, Sylvie; Gerya, Taras; Guillou-Frottier, Laurent; Cloetingh, Sierd

    The East African Rift system (EARS) provides a unique system with the juxtaposition of two contrasting yet simultaneously formed rift branches, the eastern, magma-rich, and the western, magma-poor, on either sides of the old thick Tanzanian craton embedded in a younger lithosphere. Data on the

  16. Craton Heterogeneity in the South American Lithosphere

    Science.gov (United States)

    Lloyd, S.; Van der Lee, S.; Assumpcao, M.; Feng, M.; Franca, G. S.

    2012-04-01

    We investigate structure of the lithosphere beneath South America using receiver functions, surface wave dispersion analysis, and seismic tomography. The data used include recordings from 20 temporary broadband seismic stations deployed across eastern Brazil (BLSP02) and from the Chile Ridge Subduction Project seismic array in southern Chile (CRSP). By jointly inverting Moho point constraints, Rayleigh wave group velocities, and regional S and Rayleigh wave forms we obtain a continuous map of Moho depth. The new tomographic Moho map suggests that Moho depth and Moho relief vary slightly with age within the Precambrian crust. Whether or not a correlation between crustal thickness and geologic age can be derived from the pre-interpolation point constraints depends strongly on the selected subset of receiver functions. This implies that using only pre-interpolation point constraints (receiver functions) inadequately samples the spatial variation in geologic age. We also invert for S velocity structure and estimate the depth of the lithosphere-asthenosphere boundary (LAB) in Precambrian South America. The new model reveals a relatively thin lithosphere throughout most of Precambrian South America (< 140 km). Comparing LAB depth with lithospheric age shows they are overall positively correlated, whereby the thickest lithosphere occurs in the relatively small Saõ Francisco craton (200 km). However, within the larger Amazonian craton the younger lithosphere is thicker, indicating that locally even larger cratons are not protected from erosion or reworking of the lithosphere.

  17. How to make a craton

    Science.gov (United States)

    Lee, C.; Chin, E. J.; Erdman, M.; Gaschnig, R. M.; Lederer, G. W.; Savage, P. S.; Zhong, S.; Zincone, S.

    2013-12-01

    Most Archean cratons are underlain by long-lived 200-300 km thick thermal boundary layers, significantly thicker than oceanic boundary layers, which eventually subduct. The longevity of cratons is perplexing because cold thermal boundary layers should be gravitationally unstable or should thermally erode with time. However, it is agreed that thermal contraction of the cratonic root is compensated by intrinsic compositional buoyancy due to extreme melt depletion. This melt depletion is also thought to have dehydrated the peridotitic residue, strengthening the cratonic mantle, making it resistant to thermo-mechanical erosion. Exactly how cratonic mantle arrives at this chemically buoyant and dehydrated state is unknown. Possible scenarios include formation by melting within a large plume head, accretion of oceanic lithosphere, and accretion of sub-arc mantle. The high degrees of melting would seem to imply formation in hot plume heads, but low Al and heavy rare earth element contents suggest formation in the spinel stability field, implying formation at shallower depths than their current equilibration pressures. We present a new thermobarometer designed to estimate the average melting pressures and temperatures of residual peridotites using whole rock major element compositions. We find that the average melting pressures and temperatures of cratonic peridotites range between 3-4 GPa and 1600 °C. If cratonic peridotites melted via adiabatic decompression, these average pressures represent maximum bounds on the final pressures of melt extraction. Currently, cratonic peridotites derive from 4-7 GPa, implying that the building blocks of peridotites experienced an increase of 1-3 GPa, equivalent to 30-90 km of overburden. Our results thus imply that cratonic mantle most likely formed by tectonic thickening of oceanic or arc lithospheres. But because both arc and oceanic lithospheres might be expected to be wet due to hydrous flux melting and serpentinization

  18. Fluid Characteristics in the Giant Quartz Reef System of the Bundelkhand Craton, India: Constraints from Fluid Inclusion Study

    Science.gov (United States)

    Rout, D.; Panigrahi, M. K.; Pati, J. K.

    2017-12-01

    fluid that possibly mixed with a moderate salinity fluid. Such a moderate salinity fluid could represent a magmatic fluid that evolved to such low temperatures through prolonged fluid rock interaction. Although these quartz reefs do not bear any economic grade mineralization, the fluid characteristics compare well with mineralized reefs in the Dharwar and Bastar cratons.

  19. Journal of Earth System Science | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science. R Srinivasan. Articles written in Journal of Earth System Science. Volume 109 Issue 1 March 2000 pp 57-65. Sm-Nd Ages of Two Meta-Anorthosite Complexes Around Holenarsipur: Constraints on the Antiquity of Archean Supracrustal Rocks of the Dharwar Craton.

  20. Water in the Cratonic Mantle: Insights from FTIR Data on Lac De Gras Xenoliths (Slave Craton, Canada)

    Science.gov (United States)

    Peslier, Anne H.; Brandon, Alan D.; Schaffer, Lillian Aurora; O'Reilly, Suzanne Yvette; Griffin, William L.; Morris, Richard V.; Graff, Trevor G.; Agresti, David G.

    2014-01-01

    The mantle lithosphere beneath the cratonic part of continents is the deepest (> 200 km) and oldest (>2-3 Ga) on Earth, remaining a conundrum as to how these cratonic roots could have resisted delamination by asthenospheric convection over time. Water, or trace H incorporated in mineral defects, could be a key player in the evolution of continental lithosphere because it influences melting and rheology of the mantle. Mantle xenoliths from the Lac de Gras kimberlite in the Slave craton were analyzed by FTIR. The cratonic mantle beneath Lac de Gras is stratified with shallow (water contents extending to higher values than those from the shallow ones. The FTIR spectra of olivines from the shallow samples have more prominent Group II OH bands compared to the olivines from the deep samples, consistent with a more oxidized mantle environment. The range of olivine water content is similar to that observed in Kaapvaal craton peridotites at the same depths (129-184 km) but does not extend to as high values as those from Udachnaya (Siberian craton). The Slave, Kaapvaal and Siberian cratons will be compared in terms of water content distribution, controls and role in cratonic root longevity.

  1. Metamorphism of the northern Liaoning Complex: Implications for the tectonic evolution of Neoarchean basement of the Eastern Block, North China Craton

    Directory of Open Access Journals (Sweden)

    Kam Kuen Wu

    2013-05-01

    Full Text Available As one of the areas where typical late Archean crust is exposed in the Eastern Block of the North China Craton, the northern Laioning Complex consists principally of tonalitic-trondhjemitic-granodioritic (TTG gneisses, massive granitoids and supracrustal rocks. The supracrustal rocks, named the Qingyuan Group, consist of interbedded amphibolite, hornblende granulite, biotite granulite and BIF. Petrological evidence indicates that the amphibolites experienced the early prograde (M1, peak (M2 and post-peak (M3 metamorphism. The early prograde assemblage (M1 is preserved as mineral inclusions, represented by actinotite + hornblende + plagioclase + epidote + quartz + sphene, within garnet porphyroblasts. The peak assemblage (M2 is indicated by garnet + clinopyroxene + hornblende + plagioclase + quartz + ilmenite, which occur as major mineral phases in the rock. The post-peak assemblage (M3 is characterized by the garnet + quartz symplectite. The P–T pseudosections in the NCFMASHTO system constructed by using THERMOCALC define the P–T conditions of M1, M2 and M3 at 490–550 °C/<4.5 kbar, 780–810 °C/7.65–8.40 kbar and 630–670 °C/8.15–9.40 kbar, respectively. As a result, an anticlockwise P–T path involving isobaric cooling is inferred for the metamorphic evolution of the amphibolites. Such a P–T path suggests that the late Archean metamorphism of the northern Liaoning Complex was related to the intrusion and underplating of mantle-derived magmas. The underplating of voluminous mantle-derived magmas leading to metamorphism with an anticlockwise P–T path involving isobaric cooling may have occurred in continental magmatic arc regions, above hot spots driven by mantle plumes, or in continental rift environments. A mantle plume model is favored because this model can reasonably interpret many other geological features of late Archean basement rocks from the northern Liaoning Complex in the Eastern Block of

  2. Geochemical and Sm–Nd isotopic study of titanite from granitoid ...

    Indian Academy of Sciences (India)

    in granitic magmas that have equilibrated with titanite during fractional crystallization or partial melting ... Titanite; Kolar; Ramagiri; Dharwar craton; rare earth elements; Sm–Nd isotope dating. J. Earth Syst. Sci. 120, No. 2, April 2011, pp. 237–251 c Indian Academy of Sciences ... be altered by variations in temperature and/or.

  3. Proterozoic biotite Rb-Sr dates in the northwestern part of the Yilgarn Craton, Western Australia

    International Nuclear Information System (INIS)

    Libby, W.G.; De Laeter, J.R.; Armstrong, R.A.

    1999-01-01

    Rb-Sr dating of biotite in the northwestern corner of the Yilgarn Craton identified four areas with distinctive age ranges. Biotite in the northwestern area, which includes the Narryer Terrane and part of the Murchison Terrane, yields reset Rb-Sr dates of ca 1650 Ma. In the western area, along the margin of the craton, biotite has been reset to 629 Ma. Eastward of these areas, mainly in the Murchison Terrane, the modal biotite date is near 2450 Ma, though because of a skewed distribution the mean date is closer to 2300 Ma. Dates in a transition zone between the western and eastern areas range broadly between 2000 and 1000 Ma, averaging about 1775 Ma. The western area and the transition zone are continuous with analogous areas south of the limits of the present study. The 1650 Ma dates in the northwestern area are probably related to plutonic and tectonic activity of similar age in the Gascoyne Province to the north. They may represent cooling after thermal resetting during tectonic loading by southward thrust-stacking of slices of Narryer Terrane and allochthonous Palaeoproterozoic volcanic arc and back arc rocks during the Capricorn Orogeny. This episode of crustal shortening resulted from the collision of the Yilgarn and Pilbara Cratons to form the West Australian Craton. The dates reflect cooling associated with subsequent erosion-induced rebound. The 2450 Ma biotite dates of the eastern area are similar to biotite dates found over most of the Yilgarn Craton and represent a background upon which the later dates have been superimposed. The origin of dates in the western area is unknown but may be related to an associated dolerite dyke swarm or to possible thrusting from the west. There is some evidence of minor later intrusion of felsic hypabyssal rock between 2000 and 2200 Ma and localised shearing in the Narryer area at about 1350 to 1400 Ma. One small area near Yalgoo with biotite Rb-Sr dates near 2200 Ma may be co genetic with the Muggamurra Swarm of dolerite

  4. Petrogenesis of the middle Jurassic appinite and coeval granitoids in the Eastern Hebei area of North China Craton

    Science.gov (United States)

    Fan, Wenbo; Jiang, Neng; Xu, Xiyang; Hu, Jun; Zong, Keqing

    2017-05-01

    An integrated study of zircon U-Pb ages and Hf-O isotopic compositions, whole rock elemental and Sr-Nd isotope geochemistry was conducted on three lithologically diverse middle Jurassic plutons from the Eastern Hebei area of the North China Craton (NCC), in order to reveal both their petrogenesis and possible tectonic affinity. The three plutons have consistent magmatic zircon U-Pb ages from 167 ± 1 Ma to 173 ± 1 Ma. The Nianziyu pluton has typical characteristics of appinite with low SiO2 (43.7-52.6%), high Ca, Mg, Fe and H2O contents. It possesses subduction-related trace element patterns, enriched Nd-Hf isotopic signatures as well as elevated zircon δ18O values (6.2-7.2‰), arguing for an enriched mantle source metasomatized by fluids related to subduction. The Shuihutong monzogranites have high silica (SiO2 = 75.4-75.9%) and alkali contents, low Ca contents and striking negative Ba, Sr and Eu anomalies. Samples from the pluton have more evolved Nd-Hf isotopic values and are considered to be most likely derived from anatexis of ancient lower continental crust. Hybridization between mantle- and ancient lower crust-derived magmas is proposed for the mafic microgranular enclave-bearing Baijiadian granitoids, which are characterized by variable εNd (t) and εHf(t) values. Integrated with the regional geologic history, we suggest that the formation of the three middle Jurassic plutons were related to the subduction of the Paleo-Pacific ocean plate beneath the NCC. Their petrogenetic differences reflect complex magmatic processes in subduction settings involving melting of multiple sources, possible partly facilitated by fluid metasomatism and water-rich magma injection, accompanied with various degrees of magma mixing. The appearance of middle Jurassic appinitic rocks leads us to propose that the NCC destruction and lithosphere thinning were facilitated and controlled by the weakening of the lithospheric mantle after hydration because of the subduction of the

  5. Spectral characteristics of banded iron formations in Singhbhum craton, eastern India: Implications for hematite deposits on Mars

    Directory of Open Access Journals (Sweden)

    Mahima Singh

    2016-11-01

    Full Text Available Banded iron formations (BIFs are major rock units having hematite layers intermittent with silica rich layers and formed by sedimentary processes during late Archean to mid Proterozoic time. In terrestrial environment, hematite deposits are mainly found associated with banded iron formations. The BIFs in Lake Superior (Canada and Carajas (Brazil have been studied by planetary scientists to trace the evolution of hematite deposits on Mars. Hematite deposits are extensively identified in Meridiani region on Mars. Many hypotheses have been proposed to decipher the mechanism for the formation of these deposits. On the basis of geomorphological and mineralogical studies, aqueous environment of deposition is found to be the most supportive mechanism for its secondary iron rich deposits. In the present study, we examined the spectral characteristics of banded iron formations of Joda and Daitari located in Singhbhum craton in eastern India to check its potentiality as an analog to the aqueous/marine environment on Mars. The prominent banding feature of banded iron formations is in the range of few millimeters to few centimeters in thickness. Fe rich bands are darker (gray in color compared to the light reddish jaspilitic chert bands. Thin quartz veins (<4 mm are occasionally observed in the hand-specimens of banded iron formations. Spectral investigations have been conducted in VIS/NIR region of electromagnetic spectrum in the laboratory conditions. Optimum absorption bands identified include 0.65, 0.86, 1.4 and 1.9 μm, in which 0.56 and 0.86 μm absorption bands are due to ferric iron and 1.4 and 1.9 μm bands are due to OH/H2O. To validate the mineralogical results obtained from VIS/NIR spectral radiometry, laser Raman and Fourier transform infrared spectroscopic techniques were utilized and the results were found to be similar. Goethite-hematite association in banded iron formation in Singhbhum craton suggests dehydration activity, which has

  6. Lithosphere mantle density of the North China Craton based on gravity data

    Science.gov (United States)

    Xia, B.; Artemieva, I. M.; Thybo, H.

    2017-12-01

    Based on gravity, seismic and thermal data we constrained the lithospheric mantle density at in-situ and STP condition. The gravity effect of topography, sedimentary cover, Moho and Lithosphere-Asthenosphere Boundary variation were removed from free-air gravity anomaly model. The sedimentary covers with density range from 1.80 g/cm3 with soft sediments to 2.40 g/cm3 with sandstone and limestone sediments. The average crustal density with values of 2.70 - 2.78 g/cm3 which corresponds the thickness and density of the sedimentary cover. Based on the new thermal model, the surface heat flow in original the North China Craton including western block is > 60 mW/m2. Moho temperature ranges from 450 - 600 OC in the eastern block and in the western block is 550 - 650 OC. The thermal lithosphere is 100 -140 km thick where have the surface heat flow of 60 - 70 mW/m2. The gravity effect of surface topography, sedimentary cover, Moho depth are 0 to +150 mGal, - 20 to -120 mGal and +50 to -200 mGal, respectively. By driving the thermal lithosphere, the gravity effect of the lithosphere-asthenosphere boundary ranges from 20 mGal to +200 mGal which shows strong correction with the thickness of the lithosphere. The relationship between the gravity effect of the lithosphere-asthenosphere boundary and the lithosphere thickness also for the seismic lithosphere, and the value of gravity effect is 0 to +220 mGal. The lithospheric mantle residual gravity which caused by lithospheric density variation range from -200 to +50 mGal by using the thermal lithosphere and from -250 to +100 mGal by driving the seismic lithosphere. For thermal lithosphere, the lithospheric mantle density with values of 3.21- 3.26 g/cm3 at in-situ condition and 3.33 - 3.38 g/cm3 at STP condition. Using seismic lithosphere, density of lithosphere ranges from 3.20 - 3.26 g/cm3 at in-situ condition and 3.31 - 3.41 g/cm3 at STP condition. The subcontinental lithosphere of the North China Craton is highly heterogeneous

  7. 40Ar/39Ar dating of 1.0-1.1 Ga magnetizations from the Sao Francisco and Kalahari cratons: tectonic implications for Pan-African and Brasiliano mobile belts

    International Nuclear Information System (INIS)

    Renne, P.R.; Onstott, T.C.; Agrella-Filho, M.S. d'; Pacca, I.G.; Teixeira, W.

    1990-01-01

    Paleomagnetic poles from 1.1-1.0 Ga dyke swarms in eastern Brazil (Sao Francisco Craton) are compared with 1.0 Ga poles from granulites of the Namaqua Province in southern Africa (Kalahari Graton). The intrusive ages of dykes are estimated from 40 Ar/ 39 Ar dating of outgassed biotites from baked country rocks. The age of magnetization for the granulites is derived by combining 40 Ar/ 39 Ar hornblende and biotite dates. When restored to a Mesozoic pre-drift configuration the paleomagnetic poles are in crude spatial agreement but are temporally discordant. To satisfy both paleomagnetic and geochronologic constraints, a reconstruction involving separation of the Sao Francisco and Kalahari cratons is required, indicating that the intervening Pan-African (Brasiliano) mobile belt may record a craton-craton collision. (orig.)

  8. Early tectonic history of the Marymia Inlier and correlation with the Archaean Yilgarn Craton, Western Australia

    International Nuclear Information System (INIS)

    Bagas, L.

    1999-01-01

    The Archaean granite-greenstone rocks of the Marymia Inlier outcrop within Proterozoic rocks forming the Capricorn Orogen. Five major deformation events are recognised in the rocks of the Plutonic Well and Baumgarten greenstone belts. The first two events were Late Archaean and synchronous with major epithermal gold mineralisation in the belts. Palaeoproterozoic extensional faulting was probably related to the early stages of the Capricorn Orogeny. The fourth event records a compressional phase of the Capricorn Orogeny associated with greenschist-facies metamorphism, whereas the last major event involved wrench faulting associated with minor folding. The Archaean tectonic history, rock types and timing of mineralisation strongly suggest that the Marymia Inlier is part of the Yilgarn Craton, and that each of the provinces in the craton experienced the same geological history since 2.72 Ga. The inlier is now interpreted to include two components, one is the eastern or northern extension of either the Narryer Terrane. Murchison Province or Southern Cross Province, and the other is the northwestern extension of the Eastern Goldfields Province. The Jenkin Fault, which was active in Proterozoic times, separates these two components. Copyright (1999) Blackwell Science Pty Ltd

  9. Craton stability and continental lithosphere dynamics during plume-plate interaction

    Science.gov (United States)

    Wang, H.; Van Hunen, J.; Pearson, D.

    2013-12-01

    Survival of thick cratonic roots in a vigorously convecting mantle system for billions of years has long been studied by the geodynamical community. A high cratonic root strength is generally considered to be the most important factor. We first perform and discuss new numerical models to investigate craton stability in both Newtonian and non-Newtonian rheology in the stagnant lid regime. The results show that only a modest compositional rheological factor of Δη=10 with non-Newtonian rheology is required for the survival of cratonic roots in a stagnant lid regime. A larger rheological factor (100 or more) is needed to maintain similar craton longevity in a Newtonian rheology environment. Furthermore, chemical buoyancy plays an important role on craton stability and its evolution, but could only work with suitable compositional rheology. During their long lifespan, cratons experienced a suite of dynamic, tectonothermal events, such as nearby subduction and mantle plume activity. Cratonic nuclei are embedded in shorter-lived, more vulnerable continental areas of different thickness, composition and rheology, which would influence the lithosphere dynamic when tectonothermal events happen nearby. South Africa provides a very good example to investigate such dynamic processes as it hosts several cratons and there are many episodic thermal events since the Mesozoic as indicated by a spectrum of magmatic activity. We numerically investigate such an integrated system using the topographic evolution of cratons and surrounding lithosphere as a diagnostic observable. The post-70Ma thinning of pericratonic lithosphere by ~50km around Kaapvaal craton (Mather et al., 2011) is also investigated through our numerical models. The results show that the pericratonic lithosphere cools and grows faster than cratons do, but is also more likely to be effected by episodic thermal events. This leads to surface topography change that is significantly larger around the craton than within

  10. Geological evolution of the Antongil Craton, NE Madagascar

    Science.gov (United States)

    Schofield, D.I.; Thomas, Ronald J.; Goodenough, K.M.; De Waele, B.; Pitfield, P.E.J.; Key, R.M.; Bauer, W.; Walsh, G.J.; Lidke, D.J.; Ralison, A.V.; Rabarimanana, M.; Rafahatelo, J.-M.; Randriamananjara, T.

    2010-01-01

    The Antongil Craton, along with the Masora and Antananarivo cratons, make up the fundamental Archaean building blocks of the island of Madagascar. They were juxtaposed during the late-Neoproterozoic to early Palaeozoic assembly of Gondwana. In this paper we give a synthesis of the geology of the Antongil Craton and present previously published and new geochemical and U-Pb zircon analyses to provide an event history for its evolution.The oldest rocks in the Antongil Craton form a nucleus of tonalitic gneiss, characteristic of Palaeo-Mesoarchaean cratons globally, including phases dated between 3320 ?? 14. Ma to 3231 ?? 6. Ma and 3187 ?? 2. Ma to 3154 ?? 5. Ma. A series of mafic dykes was intruded into the Mesoarchaean tonalites and a sedimentary succession was deposited on the craton prior to pervasive deformation and migmatisation of the region. The age of deposition of the metasediments has been constrained from a volcanic horizon to around 3178 ?? 2. Ma and subject to migmatisation at around 2597 ?? 49. Ma. A subsequent magmatic episode generated voluminous, weakly foliated granitic rocks, that also included additions from both reworked older crustal material and younger source components. An earlier granodiorite-dominated assemblage, dated between 2570 ?? 18. Ma and 2542 ?? 5. Ma, is largely exposed in xenoliths and more continuously in the northern part of the craton, while a later monzogranite-dominated phase, dated between 2531 ?? 13. Ma and 2513 ?? 0.4. Ma is more widely developed. Together these record the stabilisation of the craton, attested to by the intrusion of a younger dyke swarm, the age of which is constrained by a sample of metagabbro dated at 2147 ?? 6. Ma, providing the first evidence for Palaeoproterozoic rocks from the Antongil Craton.The youngest events recorded in the isotopic record of the Antongil Craton are reflected in metamorphism, neocrystallisation and Pb-loss at 792 ?? 130. Ma to 763 ?? 13. Ma and 553 ?? 68. Ma. These events are

  11. The West-African craton margin in eastern Senegal: a seismological study

    International Nuclear Information System (INIS)

    Dorbath, Catherine; Dorbath, Louis; Gaulon, Roland; Le Page, Alain

    1983-01-01

    A vertical short period seismological array was operated for six months in earstern Senegal. Large P wave travel-time anomalies are in fairly good relation with the gravity and geological features. Two-dimensional inversion of the data shows the existence of a major vertical discontinuity extending from the surface to 150-200 km depth. The other heterogeneities are mainly located in the crust and related to specific segments of the regional geology: craton, Mauritanides and Senegalo-Mauritanian basin. The main discontinuity dipping to the east is interpreted as the trace of an old subduction slab. We propose the following geodynamical process to explain the formation of the Mauritanides orogenic belt: continental collision after opening of a back-arc marginal basin in late Precambrian and its closure until Devonian

  12. A new geological framework for south-central Madagascar, and its relevance to the "out-of-Africa" hypothesis

    Science.gov (United States)

    Tucker, R.D.; Roig, J.Y.; Macey, P.H.; Delor, C.; Amelin, Y.; Armstrong, R.A.; Rabarimanana, M.H.; Ralison, A.V.

    2011-01-01

    The Precambrian shield of south-central Madagascar, excluding the Vohibory region, consists of three geologic domains, from north to south: Antananarivo, Ikalamavony-Itremo, and Anosyen-Androyen. The northern Antananarivo domain represents the Neoarchean sector of the Greater Dharwar Craton amalgamated at 2.52-2.48. Ga. The Greater Dharwar Craton is overlain by several groups of Meso- to Neoproterozoic supracrustal rocks (Ambatolampy, Manampotsy, Ampasary, Sahantaha, and Maha Groups) each with a common and diagnostic signature of Paleoproterozoic detrital zircons (2.2-1.8. Ga). The central domain (Ikalamavony-Itremo) consists of two distinct parts. The Itremo Sub-domain, in the east, is a structurally intercalated sequence of Neoarchean gneiss and shallow marine metasedimentary rocks of Paleo-Mesoproterozoic age (Itremo Group), the latter with Paleoproterozoic detrital zircons ranging in age between 2.2 and 1.8. Ga. The Ikalamavony Sub-domain, to the west, contains abundant volcano-clastic metasediments and lesser quartzite (Ikalamavony Group), formed between 1.03. Ga and 0.98. Ga, and intruded by igneous rocks (Dabolava Suite) of Stenian-Tonian age. Structurally intercalated with these are sheets of Neoarchean gneiss (~2.5. Ga) and Neoproterozoic metaclastic rocks (Molo Group). Like the Itremo Group, quartzite of the Ikalamavony Group has detrital zircons of Paleoproterozoic age (2.1-1.8. Ga). The southern domain of Anosyen-Androyen consists of a newly recognized suite of Paleoproterozoic igneous rocks (2.0-1.8. Ga), and stratified supracrustal rocks also having Paleoproterozoic detrital zircons (2.3-1.8. Ga). The contact between the Anosyen-Androyen and Ikalamavony-Itremo domains, formerly known as the Ranotsara-Bongolava shear zone, is a tightly folded and highly flattened boundary that was ductilely deformed in Ediacaran time. It is roughly equivalent to the Palghat-Cauvery shear zone in south India, and it defines approximately the boundary between the Archean

  13. THE RECENT STRUCTURE AND THE ASSUMED HISTORY OF FORMATION OF THE CRUST IN THE SOUTH-EASTERN SEGMENT OF THE NORTH ASIAN CRATON ALONG REFERENCE PROFILE 3-DV

    Directory of Open Access Journals (Sweden)

    E. Yu. Goshko

    2014-01-01

    Full Text Available The article presents results of specialized processing of the deep seismic profile along a part of Reference Profile 3-DV which crosses the Aldan-Stanovoi shield in the meridian direction and goes across its buried northern slope. The study is aimed at determining frequency-energy characteristics of the seismic wave field which are related to physical conditions of geological features of the crust. Based on analysis and interpretation of the dynamic profiles, it is possible to reveal and contour the Archean cores of consolidation of the Aldan shield and its buried continuation that is covered by sediments of the Middle Lena monocline and to input new facts in the proposed geodynamic model showing formation of the crust in the south-eastern segment of the North Asian craton.

  14. The basement of the Punta de Este Terrane: A meso proterozoic heritage at the eastern border of Rio de La Plata craton

    International Nuclear Information System (INIS)

    Preciozzi, F.; Peel, E.; Sanchez, L.; Basei, M.

    2005-01-01

    U-Pb zircon ages between 1000 and 900 Ma corresponding to the nuclei of zircon crystals extracted from the basement of the Punta del Este Terrane (Eastern Uruguay) allowed the correlation of the protoliths of this domain with rocks attributed to the Namaqua Belt in Southwestern Africa. SHRIMP ages obtained for the ortho gneissic rocks allowed to place at ca. 750 Ma the generations of gneisses and migmatites. Differently from what occurred in Africa, reworking of this crustal segment during the Brasiliano-Pan african orogenesis was very intense, reaching the granulite facies around 640Ma. Acid volcanic and volcaniclastic rocks (Sierra de Aguirre Formation) with ages around 570 Ma, late sedimentary basins (San Carlos Formation) and post-tectonic granitoids (Santa Teresa and José Ignacio batholith s) mark the end of the events related with the Brasiliano/Pan-African orogenesis. The final collision between the Punta del Este Terrane and the western domains represented by the Dom Feliciano Belt and the Río de La Plata Craton may have occurred at around 535 Ma

  15. The Thermal Structure and Strength of Cratons and their Margins

    Science.gov (United States)

    Jaupart, C. P.; Mareschal, J. C.

    2015-12-01

    The large cratons of today are made of younger terranes that wrap around older cores. Deformation due to accretion did not proceed in homogeneous fashion and was concentrated in the younger belts. This is illustrated clearly in the Archean Superior Province, Canada. In this area, one observes little imbrication of accreted crust and craton core, in contrast to the laterally extensive thrusting that has affected the younger terranes to the South. The boundary between the craton core and accreted belts is a nearly vertical interface delineated by steeply dipping electrical and seismic anomalies extending to the base of the lithosphere. These steeply dipping structures have been interpreted as relicts of the subduction that drove accretion. By contrast, the sub-crustal subduction remnant that is imaged beneath younger terranes to the south shows up as a moderately dipping (≈30°) structure. These observations suggest a stiff craton surrounded by weaker belts. This strength contrast may have affected later events, such as the Keweenawan rifing, which propagated northward through the accreted terranes but stopped short of impinging the craton core. In the Superior Province, crustal heat production is much higher in the accreted terranes than in the craton core, implying higher temperatures and lower mechanical strength. Such a remarkable dichotomy also exists in South Africa, where the Limpopo and Namaqua belts are characterized by higher heat flux and crustal heat production than the adjacent Archean Kaapvaal and Zimbabwe cratons. The generality of this cannot be assessed on the basis of heat flow and heat production data which are scarce in most other cratons. These cratons, however, are characterized by post-orogenic high temperature metamorphism which is best explained by high crustal heat production. This is true, for example, for the Jimperding metamorphic belt at the edge of the Yilgarn craton, Western Australia. Thus, cratons appear to be surrounded, and

  16. Probing the edge of the West African Craton: A first seismic glimpse from Niger

    Science.gov (United States)

    Di Leo, Jeanette F.; Wookey, James; Kendall, J.-Michael; Selby, Neil D.

    2015-03-01

    Constraints on crustal and mantle structure of the Eastern part of the West African Craton have to date been scarce. Here we present results of P receiver function and SK(K)S wave splitting analyses of data recorded at International Monitoring System array TORD in SW Niger. Despite lacking in lateral coverage, our measurements sharply constrain crustal thickness (˜41 km), VP/VS ratio (1.69 ± 0.03), mantle transition zone (MTZ) thickness (˜247 km), and a midlithospheric discontinuity at ˜67 km depth. Splitting delay times are low with an average of 0.63 ± 0.01 s. Fast directions follow the regional surface geological trend with an average of 57 ± 1°. We suggest that splitting is due to fossil anisotropic fabrics in the crust and lithosphere, incurred during the Paleoproterozoic Eburnean Orogeny, with possible contributions from the later Pan-African Orogeny and present-day mantle flow. The MTZ appears to be unperturbed, despite the proximity of the sampled region to the deep cratonic root.

  17. Gravimetric study on the western edge of the Rio de La Plata craton

    International Nuclear Information System (INIS)

    Rame, G; Miro, R

    2010-01-01

    This work is about the gravimetric study on the western edge of the Rio de la Plata craton which belongs to the Gondwana fragment in the south of Brazil, Uruguay and central eastern of Argentina. The work consisted of a survey of 332 gravimetric and topographic stations extended from the western edge of the Sierra Chica de Cordoba up to 200 km east on the pampas. The gravity values observed (gobs) were obtained using a LaCoste §Rom berg gravimeter G-961 and 200T Sodin both with 0.01 mGal, referred to IGSN71 (International Gravity Standardization Net 1971) network

  18. Density heterogeneity of the cratonic lithosphere

    DEFF Research Database (Denmark)

    Cherepanova, Yulia; Artemieva, Irina

    2015-01-01

    Using free-board modeling, we examine a vertically-averaged mantle density beneath the Archean-Proterozoic Siberian craton in the layer from the Moho down to base of the chemical boundary layer (CBL). Two models are tested: in Model 1 the base of the CBL coincides with the LAB, whereas in Model 2...... the base of the CBL is at a 180 km depth. The uncertainty of density model is density structure of the Siberian lithospheric mantle with a strong...... correlation between mantle density variations and the tectonic setting. Three types of cratonic mantle are recognized from mantle density anomalies. 'Pristine' cratonic regions not sampled by kimberlites have the strongest depletion with density deficit of 1.8-3.0% (and SPT density of 3.29-3.33 t/m3...

  19. The electrical lithosphere in Archean cratons: examples from Southern Africa

    Science.gov (United States)

    Khoza, D. T.; Jones, A. G.; Muller, M. R.; Webb, S. J.

    2011-12-01

    The southern African tectonic fabric is made up of a number Archean cratons flanked by Proterozoic and younger mobile belts, all with distinctly different but related geological evolutions. The cratonic margins and some intra-cratonic domain boundaries have played major roles in the tectonics of Africa by focusing ascending magmas and localising cycles of extension and rifting. Of these cratons the southern extent of the Congo craton is one of the least-constrained tectonic boundaries in the African tectonic architecture and knowledge of its geometry and in particular the LAB beneath is crucial for understanding geological process of formation and deformation prevailing in the Archean and later. In this work, which forms a component of the hugely successful Southern African MagnetoTelluric Experiment (SAMTEX), we present the lithospheric electrical resistivity image of the southern boundary of the enigmatic Congo craton and the Neoproterozoic Damara-Ghanzi-Chobe (DGC) orogenic belt on its flanks. Magnetotelluric data were collected along profiles crossing all three of these tectonic blocks. The two dimensional resistivity models resulting from inverting the distortion-corrected responses along the profiles all indicate significant lateral variations in the crust and upper mantle structure along and across strike from the younger DGC orogen to the older adjacent craton. The are significant lithospheric thickness variations from each terrane. The The Moho depth in the DGC is mapped at 40 km by active seismic methods, and is also well constrained by S-wave receiver function models. The Damara belt lithosphere, although generally more conductive and significantly thinner (approximately 150 km) than the adjacent Congo and Kalahari cratons, exhibits upper crustal resistive features interpreted to be caused by igneous intrusions emplaced during the Gondwanan Pan-African magmatic event. The thinned lithosphere is consistent with a 50 mW.m-2 steady-state conductive

  20. Imaging the lithosphere-asthenosphere boundary across the transition from Phanerozoic Europe to the East-European Craton with S-receiver functions

    Science.gov (United States)

    Knapmeyer-Endrun, Brigitte; Krüger, Frank

    2013-04-01

    Cratons are characterized by their thick lithospheric roots. In the case of the Eastern European Craton, high seismic velocities have been imaged tomographically to more than 200 km depth. However, the exact depth extent of the cratonic lithosphere and especially the properties of the transition to a much thinner lithosphere beneath Phanerozoic central Europe still remain under discussion. Whereas a number of recent seismic campaigns has significantly increased the knowledge about crustal structure and Moho topography in central Europe, comparably detailed, 3-D information on upper mantle structure, e.g. the lithosphere-asthenosphere boundary (LAB), is yet missing. The international PASSEQ experiment, which was conducted from 2006 to 2008, strived to fill this gap with the deployment of 196 seismological stations, roughly a quarter of which were equipped with broad-band sensors, between eastern Germany and Lithuania. With a mean inter-station distance of 60 km, reduced to about 20 km along the central profile, PASSEQ offers the densest coverage for a passive experiment in this region yet. Here, we present first S-receiver function results for this data set, complemented by additional data from national and regional networks and other temporary deployments. This increases the number of available broad-band stations to almost 300, though mostly located to the west of the Trans-European Suture Zone (TESZ). Besides, we also process data from short-period (1 s and 5 s) sensors. The visibility of mantle-transition zone phases, even in single-station data, provides confidence in the quality of the obtained S-receiver functions. Moho conversions can be confidently identified for all stations. In case of a low-velocity sedimentary cover, as found for example in the Polish Basin, the S-receiver functions even provide clearer information on Moho depth than the P-receiver functions, which are heavily disturbed by shallow reverberations. For stations west of the TESZ, a clear

  1. Sr-Nd-Pb isotopes of the post-paleozoic magmatism from eastern Paraguay

    International Nuclear Information System (INIS)

    Comin-Chiaramonti, P; Gasparon, M; Gomes, C.B; Antonini, P

    2001-01-01

    The Parana Angola-Namibia igneous province (PAN) is characterized by Early Cretaceous flood tholeiites and tholeiitic dyke swarms associated with alkaline rocks of Early and Late Cretaceous ages, respectively, and with scarce post-Mesozoic magmatic rocks (Comin-Chiaramonti et al., 1997; 1999; Marques et al., 1999). The Eastern Paraguay, at the westernmost side of the Parana Basin, is of special interest because: (1) it is located between two main cratonic blocks, i.e. the southernmost tip of the Amazon Craton, and the northermost exposure of the Rio de La Plata Craton; (2) it was the site of repeated Na-K-alkaline magmatism since Late-Permian-Triassic times (i.e.: 250-240 Ma, Na-alkaline; c. 145 Ma, K-alkaline; 128-126 Ma, K-alkaline; 120-90 Ma, Na-alkaline; 61-33 Ma, Na-alkaline; cf. Comin-Chiaramonti and Gomes, 1996; Comin-Chiaramonti et al., 1999), and of Early Cretaceous tholeiitic magmatism, both low- and high-Ti variants, L-Ti and H-Ti, respectively (133-131 Ma; cf. Marzoli et al., 1999); (3) the younger sodic magmatic rocks are closely associated in space to the potassic analogues (Comin- Chiaramonti et al., 1999). The paper aims discussing the most important Sr- Nd-Pb isotope features of the alkaline and tholeiitic magmas from Eastern Paraguay in comparison with the PAN analogues (au)

  2. Regionalization of Crustal and Upper Mantle Q Structure in Eastern Eurasia Using Multiple Regional Waves

    National Research Council Canada - National Science Library

    Gaherty, James; Lerner-Lam, Arthur

    2007-01-01

    .... The Q Omicron model contains values that vary between 100 and 900. Q Omicron are the lowest in the Tibetan plateau, increase to moderate levels towards the east and north, and reach maxima in the Siberian and eastern Europe Cratons...

  3. EVOLUTION OF SOUTHERN AFRICAN CRATONS BASED ON SEISMIC IMAGING

    DEFF Research Database (Denmark)

    Thybo, Hans; Soliman, Mohammad Youssof Ahmad; Artemieva, Irina

    2014-01-01

    present a new seismic model for the structure of the crust and lithospheric mantle of the Kalahari Craton, constrained by seismic receiver functions and finite-frequency tomography based on the seismological data from the South Africa Seismic Experiment (SASE). The combination of these two methods...... since formation of the craton, and (3) seismically fast lithospheric keels are imaged in the Kaapvaal and Zimabwe cratons to depths of 300-350 km. Relatively low velocity anomalies are imaged beneath both the paleo-orogenic Limpopo Belt and the Bushveld Complex down to depths of ~250 km and ~150 km...

  4. Formation of cratonic lithosphere: An integrated thermal and petrological model

    Science.gov (United States)

    Herzberg, Claude; Rudnick, Roberta

    2012-09-01

    The formation of cratonic mantle peridotite of Archean age is examined within the time frame of Earth's thermal history, and how it was expressed by temporal variations in magma and residue petrology. Peridotite residues that occupy the lithospheric mantle are rare owing to the effects of melt-rock reaction, metasomatism, and refertilization. Where they are identified, they are very similar to the predicted harzburgite residues of primary magmas of the dominant basalts in greenstone belts, which formed in a non-arc setting (referred to here as "non-arc basalts"). The compositions of these basalts indicate high temperatures of formation that are well-described by the thermal history model of Korenaga. In this model, peridotite residues of extensive ambient mantle melting had the highest Mg-numbers, lowest FeO contents, and lowest densities at ~ 2.5-3.5 Ga. These results are in good agreement with Re-Os ages of kimberlite-hosted cratonic mantle xenoliths and enclosed sulfides, and provide support for the hypothesis of Jordan that low densities of cratonic mantle are a measure of their high preservation potential. Cratonization of the Earth reached its zenith at ~ 2.5-3.5 Ga when ambient mantle was hot and extensive melting produced oceanic crust 30-45 km thick. However, there is a mass imbalance exhibited by the craton-wide distribution of harzburgite residues and the paucity of their complementary magmas that had compositions like the non-arc basalts. We suggest that the problem of the missing basaltic oceanic crust can be resolved by its hydration, cooling and partial transformation to eclogite, which caused foundering of the entire lithosphere. Some of the oceanic crust partially melted during foundering to produce continental crust composed of tonalite-trondhjemite-granodiorite (TTG). The remaining lithosphere gravitationally separated into 1) residual eclogite that continued its descent, and 2) buoyant harzburgite diapirs that rose to underplate cratonic nuclei

  5. The Role of Water in the Stability of Cratonic Keels

    Science.gov (United States)

    Peslier, Anne H.; Woodland, Alan B.; Bell, David R.; Lazarov, Marina

    2011-01-01

    Cratons are typically underlain by large, deep, and old lithospheric keels (to greater than 200 km depth, greater than 2.5 Ga old) projecting into the asthenosphere (e.g., Jordan, 1978; Richardson et al., 1984). This has mystified Earth scientists as the dynamic and relatively hot asthenosphere should have eroded away these keels over time (e.g., Sleep, 2003; O'Neill et al., 2008; Karato, 2010). Three key factors have been invoked to explain cratonic root survival: 1) Low density makes the cratonic mantle buoyant (e.g., Poudjom Djomani et al., 2001). 2) Low temperatures (e.g., Pollack, 1986; Boyd, 1987), and 3) low water contents (e.g., Pollack, 1986), would make cratonic roots mechanically strong. Here we address the mechanism of the longevity of continental mantle lithosphere by focusing on the water parameter. Although nominally anhydrous , olivine, pyroxene and garnet can accommodate trace amounts of water in the form of H bonded to structural O in mineral defects (e.g., Bell and Rossman, 1992). Olivine softens by orders of magnitude if water (1-1000 ppm H2O) is added to its structure (e.g., Mackwell et al., 1985). Our recent work has placed constraints on the distribution of water measured in peridotite minerals in the cratonic root beneath the Kaapvaal in southern Africa (Peslier et al., 2010). At P greater than 5 GPa, the water contents of pyroxene remain relatively constant while those of olivine systematically decrease from 50 to less than 10 ppm H2O at 6.4 GPa. We hypothesized that at P greater than 6.4 GPa, i.e. at the bottom of the cratonic lithosphere, olivines are essentially dry (greater than 10 ppm H2O). As olivine likely controls the rheology of the mantle, we calculated that the dry olivines could be responsible for a contrast in viscosity between cratonic lithosphere and surrounding asthenosphere large enough to explain the resistance of cratonic root to asthenospheric delamination.

  6. Rhyacian evolution of the eastern São Luís Craton: petrography, geochemistry and geochronology of the Rosário Suite

    Directory of Open Access Journals (Sweden)

    Bruna Karine Correa Nogueira

    Full Text Available ABSTRACT: The São Luís Cráton comprises an area between northeast Pará state and northwest Maranhão that exposes Paleoproterozoic granitic suites and meta-volcanosedimentary sequences. In the east of this geotectonic unit, about 70 km south of São Luís, there is a portion of the São Luís Craton, represented by the intrusive Rosario Suite (RS. This work is focused on rocks of this suite, including petrographic, lithochemical and geochronological studies to understand the crustal evolution of these granitoid rocks. The rock spectrum varies from tonalitic to granodioritic, quartz dioritic and granitic compositions, and there are partial structural and mineralogical changes related to deformation along transcurrent shear zones. The geochemical studies show granitic metaluminous compositions of the calc-alkaline series with I-type affinity typical of magmatic arc. Rare earth elements show marked fractionation and slight Eu positive or negative anomalies (Eu/Eu* = 0.82 to 1.1. Zircon U-Pb data provided consistent ages of 2165 ± 7 Ma, 2170 ± 7 Ma, 2170 ± 7 Ma, 2161 ± 4 Ma and 2175 ± 8 Ma, dating emplacement of these granitoids as Paleoproterozoic (Rhyacian. Sm-Nd isotopic data provided model ages (TDM of 2.21 to 2.31 Ga with positive values of εNd +1.9 to +3.2 (t = 2.17 Ga, indicating predominantly Rhyacian crustal sources for the parental magmas, similar to those ones found in other areas of the São Luís Craton. The data, integrated with published geological and geochronological information, indicate the occurrence of an important continental crust formation event in this area. The Paleoproterozoic evolution between 2.17 and 2.15 Ga is related to the Transamazonian orogeny. The granitoids of the Rosario Suite represent the main phase of continental arc magmatism that has continuity in other parts of the São Luís Craton and can be correlated with Rhyacian accretionary magmatism in the northwestern portion of the Amazonian Craton that

  7. Three-Dimensional Rheological Structure of North China Craton Determined by Integration of Multiple observations: Controlling Role for Lithospheric Rifting

    Science.gov (United States)

    Xiong, X.; Shan, B.; Li, Y.

    2017-12-01

    The North China Craton (NCC) has undergone significant lithospheric rejuvenation in late Mesozoic and Cenozoic, one feature of which is the widespread extension and rifting. The extension is distinct between the two parts of NCC: widespread rifting in the eastern NCC and localized narrow rifting in the west. The mechanism being responsible for this difference is uncertain and highly debated. Since lithospheric deformation can be regarded as the response of lithosphere to various dynamic actions, the rheological properties of lithosphere must have a fundamental influence on its tectonics and deformation behavior. In this study, we investigated the 3D thermal and rheological structure of NCC by developing a model integrating several geophysical observables (such as surface heatflow, regional elevation, gravity and geoid anomalies, and seismic tomography models). The results exhibit obvious lateral variation in rheological structure between the eastern and western NCC. The overall lithospheric strength is higher in the western NCC than in the east. Despite of such difference in rheology, both parts of NCC are characterized by mantle dominated strength regime, which facilitates the development of narrow rifting. Using ancient heatflow derived from mantle xenoliths studies, and taking the subduction-related dehydration reactions during Mesozoic into account, we constructed the thermal and rheological structure of NCC in Ordovician, early Cretaceous and early Cenozoic. Combining the evidence from numerical simulations, we proposed an evolution path of the rifting in NCC. The lithosphere of NCC in Ordovician was characterized by a normal craton features: low geotherm, high strength and mantle dominated regime. During Jurassic and Cretaceous, the mantle lithosphere in the eastern NCC was hydrated by fluid released by the suduction of the Pacific plate, resulting in weakening of the lithosphere and a transition from mantle dominated to crust dominated regime, which

  8. The 3-dimensional construction of the Rae craton, central Canada

    Science.gov (United States)

    Snyder, David B.; Craven, James A.; Pilkington, Mark; Hillier, Michael J.

    2015-10-01

    Reconstruction of the 3-dimensional tectonic assembly of early continents, first as Archean cratons and then Proterozoic shields, remains poorly understood. In this paper, all readily available geophysical and geochemical data are assembled in a 3-D model with the most accurate bedrock geology in order to understand better the geometry of major structures within the Rae craton of central Canada. Analysis of geophysical observations of gravity and seismic wave speed variations revealed several lithospheric-scale discontinuities in physical properties. Where these discontinuities project upward to correlate with mapped upper crustal geological structures, the discontinuities can be interpreted as shear zones. Radiometric dating of xenoliths provides estimates of rock types and ages at depth beneath sparse kimberlite occurrences. These ages can also be correlated to surface rocks. The 3.6-2.6 Ga Rae craton comprises at least three smaller continental terranes, which "cratonized" during a granitic bloom. Cratonization probably represents final differentiation of early crust into a relatively homogeneous, uniformly thin (35-42 km), tonalite-trondhjemite-granodiorite crust with pyroxenite layers near the Moho. The peak thermotectonic event at 1.86-1.7 Ga was associated with the Hudsonian orogeny that assembled several cratons and lesser continental blocks into the Canadian Shield using a number of southeast-dipping megathrusts. This orogeny metasomatized, mineralized, and recrystallized mantle and lower crustal rocks, apparently making them more conductive by introducing or concentrating sulfides or graphite. Little evidence exists of thin slabs similar to modern oceanic lithosphere in this Precambrian construction history whereas underthrusting and wedging of continental lithosphere is inferred from multiple dipping discontinuities.

  9. Cover sequences at the northern margin of the Antongil Craton, NE Madagascar

    Science.gov (United States)

    Bauer, W.; Walsh, G.J.; De Waele, B.; Thomas, Ronald J.; Horstwood, M.S.A.; Bracciali, L.; Schofield, D.I.; Wollenberg, U.; Lidke, D.J.; Rasaona, I.T.; Rabarimanana, M.H.

    2011-01-01

    The island of Madagascar is a collage of Precambrian, generally high-grade metamorphic basement domains, that are locally overlain by unmetamorphosed sedimentary rocks and poorly understood low-grade metasediments. In the Antalaha area of NE Madagascar, two distinct cover sequences rest on high-grade metamorphic and igneous basement rocks of the Archaean Antongil craton and the Neoproterozoic Bemarivo belt. The older of these two cover sequences, the Andrarona Group, consists of low-grade metasedimentary rocks. The younger sequence, the newly defined Ampohafana Formation, consists of unmetamorphosed sedimentary rocks. The Andrarona Group rests on Neoarchaean granites and monzogranites of the Antongil craton and consists of a basal metagreywacke, thick quartzites and an upper sequence of sericite-chlorite meta-mudstones, meta-sandstones and a volcaniclastic meta-sandstone. The depositional age of the volcaniclastic meta-sandstone is constrained in age by U–Pb laser-ablation ICP-MS analyses of euhedral zircons to 1875 ± 8 Ma (2σ). Detrital zircons of Archaean and Palaeoproterozoic age represent an input from the Antongil craton and a newly defined Palaeoproterozoic igneous unit, the Masindray tonalite, which underlies the Andrarona Group, and yielded a U–Pb zircon age of 2355 ± 11 Ma (2σ), thus constraining the maximum age of deposition of the basal part of the Andrarona Group. The Andrarona Group shows a low-grade metamorphic overprint in the area near Antalaha; illite crystallinity values scatter around 0.17°Δ2Θ CuKα, which is within the epizone. The Ampohafana Formation consists of undeformed, polymict conglomerate, cross-bedded sandstone, and red mudstone. An illite crystallinity value of >0.25°Δ2Θ CuKα obtained from the rocks is typical of the diagenetic zone. Occurrences of rhyodacite pebbles in the Ampohafana Formation and the intrusion of a basaltic dyke suggest a deposition in a WSW-ENE-trending graben system during the opening of the Indian

  10. Do cratons preserve evidence of stagnant lid tectonics?

    Directory of Open Access Journals (Sweden)

    Derek Wyman

    2018-01-01

    Full Text Available Evidence for episodic crustal growth extending back to the Hadean has recently prompted a number of numerically based geodynamic models that incorporate cyclic changes from stagnant lid to mobile lid tectonics. A large part of the geologic record is missing for the times at which several of these cycles are inferred to have taken place. The cratons, however, are likely to retain important clues relating to similar cycles developed in the Mesoarchean and Neoarchean. Widespread acceptance of a form of plate tectonics by ∼3.2 Ga is not at odds with the sporadic occurrence of stagnant lid tectonics after this time. The concept of scale as applied to cratons, mantle plumes and Neoarchean volcanic arcs are likely to provide important constraints on future models of Earth's geodynamic evolution. The Superior Province will provide some of the most concrete evidence in this regard given that its constituent blocks may have been locked into a stagnant lid relatively soon after their formation and then assembled in the next global plate tectonic interval. Perceived complexities associated with inferred mantle plume – volcanic arc associations in the Superior Province and other cratons may be related to an over estimation of plume size. A possible stagnant lid episode between ∼2.9 Ga and ∼2.8 Ga is identified by previously unexplained lapses in volcanism on cratons, including the Kaapvaal, Yilgarn and Superior Province cratons. If real, then mantle dynamics associated with this episode likely eliminated any contemporaneous mantle plume incubation sites, which has important implications for widespread plumes developed at ∼2.7 Ga and favours a shallow mantle source in the transition zone. The Superior Province provides a uniquely preserved local proxy for this global event and could serve as the basis for detailed numerical models in the future.

  11. The Teles Pires volcanic province: A paleogeoproterozoic silicic-dominated large igneous province in southwest Amazon craton and tectonic implications

    International Nuclear Information System (INIS)

    Leite, Jayme Alfredo Dexheimer; Saes, Gerson Souza; Macambira, Moacir Jose Buenano

    2001-01-01

    Large Igneous Provinces (LIPs) are important features of the Earth history especially recognized during Paleo to Mezosoic times when they are related to the break up of supercontinents (Coffin and Eldhom, 1994). These provinces occur in several different tectonic settings such as volcanic passive margins, submarine ridges and continental and oceanic plateaux. Mafic-dominanted provinces are the most well known among the LIPs and the best examples are the Karoo, Kerguelem and Ontong-Java. LIPs including an important silicic component have been described in some basaltic provinces of southern Africa (Milner et al. 1992). More recently, silicic-dominated LIPs have been recognized in eastern Australia (Bryan et al., 2000), in southern South America (Pankhurst et al. 1998) and in Antartica Penninsula (Riley and Leat, 1999). The common characteristics of this kind of LIP include: 1) large volume of silicic rocks with dominance of ignimbrites, 2) active over 40 to 50 m.y.; and 3) spatially and temporally associated with plate break up. In this paper we present the main geologic and geochronologic characteristics of the Teles Pires volcanic province from southwest Amazon Craton, which allow its classification as a Paleoprotorozoic silicic-dominated LIP. Geologic implications of this suggestion includes the existence of a large cratonic plate as old as 1.81Ga for the Amazon Craton, therefore the proposed 1.85-1.55 Ga magmatic arc of Rio Negro-Juruena Province should be reviewed (au)

  12. Origins of cratonic mantle discontinuities: A view from petrology, geochemistry and thermodynamic models

    Science.gov (United States)

    Aulbach, Sonja; Massuyeau, Malcolm; Gaillard, Fabrice

    2017-01-01

    Geophysically detectible mid-lithospheric discontinuities (MLD) and lithosphere-asthenosphere boundaries (LAB) beneath cratons have received much attention over recent years, but a consensus on their origin has not yet emerged. Cratonic lithosphere composition and origin is peculiar due to its ultra-depletion during plume or accretionary tectonics, cool present-day geothermal gradients, compositional and rheological stratification and multiple metasomatic overprints. Bearing this in mind, we integrate current knowledge on the physical properties, chemical composition, mineralogy and fabric of cratonic mantle with experimental and thermodynamic constraints on the formation and migration of melts, both below and within cratonic lithosphere, in order to find petrologically viable explanations for cratonic mantle discontinuities. LABs characterised by strong seismic velocity gradients and increased conductivity require the presence of melts, which can form beneath intact cratonic roots reaching to 200-250 km depth only in exceptionally warm and/or volatile-rich mantle, thus explaining the paucity of seismical LAB observations beneath cratons. When present, pervasive interaction of these - typically carbonated - melts with the deep lithosphere leads to densification and thermochemical erosion, which generates topography at the LAB and results in intermittent seismic LAB signals or conflicting seismic, petrologic and thermal LAB depths. In rare cases (e.g. Tanzanian craton), the tops of live melt percolation fronts may appear as MLDs and, after complete lithosphere rejuvenation, may be sites of future, shallower LABs (e.g. North China craton). Since intact cratons are presently tectonomagmatically quiescent, and since MLDs produce both positive and negative velocity gradients, in some cases with anisotropy, most MLDs may be best explained by accumulations (metasomes) of seismically slow minerals (pyroxenes, phlogopite, amphibole, carbonates) deposited during past

  13. Late Ordovician brachiopods from eastern North Greenland

    DEFF Research Database (Denmark)

    Mac Ørum Rasmussen, Christian

    2013-01-01

    Late Ordovician rhynchonelliformean brachiopods, typical of the North American Red River fauna, are found sporadically in the BOrglum River Formation of the Centrum SO area, Kronprins Christian Land, eastern North Greenland. The geographical distribution of this characteristic brachiopod fauna......) to younger strata exclusively yielding specimens of H.gigas. As H.gigas occurs in the upper part of the Cape Calhoun Formation in Washington Land, it indicates that the upper boundary of the Cape Calhoun Formation is considerably younger than previous estimates, reaching into the uppermost Katian (middle...... (Richmondian), it possesses a strong provincial signal during the later Ordovician. The new occurrences indicate that this fauna extended to the north-eastern margin of the Laurentian Craton. It lived in close association with cosmopolitan faunal elements that may have been the earliest sign of the succeeding...

  14. The Vendian-Early Palaeozoic sedimentary basins of the East European Craton

    NARCIS (Netherlands)

    Sliaupa, S.; Fokin, P.A.; Lazauskiene, J.; Stephenson, R.A.

    2006-01-01

    Vendian-Early Palaeozoic sedimentation on the East European Craton (EEC) was confined to the cratonic margins with limited intracratonic subsidence. Generally, there are two geodynamic stages involved: in stage 1, basins formed in response to continental break-up processes; in stage 2, basins formed

  15. Granulite belts of Central India with special reference to the Bhopalpatnam Granulite Belt: Significance in crustal evolution and implications for Columbia supercontinent

    Science.gov (United States)

    Vansutre, Sandeep; Hari, K. R.

    2010-11-01

    The Central Indian collage incorporates the following major granulite belts: (1) the Balaghat-Bhandara Granulite Belt (BBG), (2) the Ramakona-Katangi Granulite Belt (RKG), (3) the Chhatuabhavna Granulite (CBG) of Bilaspur-Raigarh Belt, (4) the Makrohar Granulite Belt (MGB) of Mahakoshal supracrustals, (5) the Kondagaon Granulite Belt (KGGB), (6) the Bhopalpatnam Granulite Belt (BGB), (7) the Konta Granulite Belt (KTGB) and (8) the Karimnagar Granulite Belt (KNGB) of the East Dharwar Craton (EDC). We briefly synthesize the general geologic, petrologic and geochronologic features of these belts and explain the Precambrian crustal evolution in Central India. On the basis of the available data, a collisional relationship between Bastar craton and the EDC during the Paleo-Mesoproterozoic is reiterated as proposed by the earlier workers. The tectonic evolution of only few of the orogenic belts (BGB in particular) of Central India is related to Columbia.

  16. Electromagnetic evidence of high angle convergence between the Congo and Kalahari cratons in southern Africa

    Science.gov (United States)

    Khoza, D. T.; Jones, A. G.; Muller, M. R.; Miensopust, M. P.; Webb, S. J.; Share, P.

    2010-12-01

    The southern African tectonic fabric is made up of a number Archean cratons flanked by Proterozoic and younger mobile belts, all with distinctly different but related geological evolutions. The cratonic margins and some intra-cratonic domain boundaries have played major roles in the tectonics of Africa by focusing ascending magmas and localising cycles of extension and rifting. Of these cratons the southern extent of the Congo craton is one of the least-constrained tectonic boundaries in the African tectonic architecture and knowledge of its geometry is crucial for understanding geological process of formation and deformation prevailing in the Archean and later. In this work, which forms a component of the hugely successful Southern African MagnetoTelluric Experiment (SAMTEX), we present the first-ever lithospheric electrical resistivity image of the southern boundary of the enigmatic Congo craton and the Neoproterozoic Damara-Ghanzi-Chobe (DGC) orogenic belt on its flanks. The DGC belt is highly complex and records the transpressive collision between the Congo to the north and Kalahari craton to the south. Magnetotelluric data were collected along a profile crossing all three of these tectonic blocks. The two-dimensional resistivity models resulting from inverting the distortion-corrected responses along the profiles all indicate significant lateral variations in the crust and upper mantle structure along and across strike from the younger DGC orogen to the older adjacent craton. The Moho depth in the DGC is mapped at 40 km by active seismic methods, and is also well constrained by S-wave receiver function models. The Damara belt lithosphere, although generally more conductive and significantly thinner (approximately 150 km) than the adjacent Congo and Kalahari cratons, exhibits upper crustal resistive features interpreted to be caused by igneous intrusions emplaced during the Gondwanan Pan-African magmatic event. The thinned lithosphere is consistent with a 50 m

  17. What is a craton? How many are there? How do they relate? And how did they form?

    Science.gov (United States)

    Bleeker, W.; Davis, B. W.

    2004-05-01

    What is a craton? A craton is a large, coherent domain of Earth's continental crust that has attained and maintained long-term stability, having undergone little internal deformation, except perhaps near its margins due to interaction with neighbouring terranes. Stable continental crust is an end product of intense magmatic, tectonic, and metamorphic reworking; hence, cratons consist of polydeformed and metamorphosed crystalline and metamorphic rocks (e.g., typically "granite-greenstone terrains" in the most ancient cratons). Reworked crust only becomes a craton once the cumulative tectonic, magmatic, and metamorphic reprocessing has self-organized the crust and underlying lithosphere into a stable density, compositional, and thermal profile. Major late-stage "granite bloom" events play a critical role in attaining such stable lithospheric profiles. Once above average stability has been reached, deformation will be concentrated in adjacent domains with weaker strength profiles. Significant rifting events, assisted by mantle plume activity and mafic dyke swarms, are then needed to break up cratonic lithosphere. Where cratons are exposed, they form "shields" dominated by crystalline and metamorphic rocks; where younger, weakly deformed cover overlies cratonic basement, these areas are referred to as "platforms". Shields and platforms are physiographic terms rather than tectonic entities. Another concept, related but not identical to cratons is that of "structural provinces" and the two are commonly confused. Perhaps there is a slight bias for Archean cratons with buoyant mantle keels to form relatively high-standing areas, thus forming shields. However, large parts of Archean cratons are buried underneath platformal cover. There is no strict age connotation to the term "craton", and implied age depends on context. In a context of mantle keels, diamonds and kimberlites, there often is an implicit tendency to equate cratons with stable crust of Archean age. Elsewhere

  18. 3-D Structure of the Slave and Rae Cratons Provides Clues to Their Construction

    Science.gov (United States)

    Snyder, D. B.

    2013-12-01

    Deep geologic structures within cratons that make up continental cores were long neglected. Recently acquired geophysical data from large observational arrays and geochemical data resulting from exploration for diamond has now made possible co-registration of large-scale (400-km depth), truly 3-dimensional data sets. P-waves, surface waves and magnetotelluric observations provide 3-D wavespeed and conductivity models. Multi-azimuthal receiver functions map seismic discontinuity surfaces in 3-D. Xenolith suites erupted in kimberlites provide rock samples at key lithospheric depths, albeit at sparsely distributed locations. These multi-disciplinary models are becoming available for several key cratons worldwide; here the deep structure of the Slave and Rae cratons of the Canadian Shield is described. Lithospheric layers with tapered, wedge-shaped margins are common. Slave craton layers are sub-horizontal and indicate construction of the craton core at 2.7 Ga by underthrusting and flat stacking of lithosphere. The central Rae craton has predominantly dipping discontinuities that indicate construction at 1.9 Ga by thrusting similar to that observed in crustal ';thick-skinned' fold-and-thrust belts. 3-D mapping of conductivity and metasomatism, the latter via mineral recrystallization and resetting of isotopic ages, overprints primary structures in both cratons. Distribution of more conductivitve mantle suggests that assumed causative pervasive metasomatism occurs at 100-200 km depths with ';chimneys' reaching to shallower depths, typically in locations where kimberlites or mineralization has occurred.

  19. Evolution of Meso-Cenozoic lithospheric thermal-rheological structure in the Jiyang sub-basin, Bohai Bay Basin, eastern North China Craton

    Science.gov (United States)

    Xu, Wei; Qiu, Nansheng; Wang, Ye; Chang, Jian

    2018-01-01

    The Meso-Cenozoic lithospheric thermal-rheological structure and lithospheric strength evolution of the Jiyang sub-basin were modeled using thermal history, crustal structure, and rheological parameter data. Results indicate that the thermal-rheological structure of the Jiyang sub-basin has exhibited obvious rheological stratification and changes over time. During the Early Mesozoic, the uppermost portion of the upper crust, middle crust, and the top part of the upper mantle had a thick brittle layer. During the early Early Cretaceous, the top of the middle crust's brittle layer thinned because of lithosphere thinning and temperature increase, and the uppermost portion of the upper mantle was almost occupied by a ductile layer. During the late Early Cretaceous, the brittle layer of the middle crust and the upper mantle changed to a ductile one. Then, the uppermost portion of the middle crust changed to a thin brittle layer in the late Cretaceous. During the early Paleogene, the thin brittle layer of the middle crust became even thinner and shallower under the condition of crustal extension. Currently, with the decrease in lithospheric temperature, the top of the upper crust, middle crust, and the uppermost portion of the upper mantle are of a brittle layer. The total lithospheric strength and the effective elastic thickness ( T e) in Meso-Cenozoic indicate that the Jiyang sub-basin experienced two weakened stages: during the late Early Cretaceous and the early Paleogene. The total lithospheric strength (approximately 4-5 × 1013 N m-1) and T e (approximately 50-60 km) during the Early Mesozoic was larger than that after the Late Jurassic (2-7 × 1012 N m-1 and 19-39 km, respectively). The results also reflect the subduction, and rollback of Pacific plate is the geodynamic mechanism of the destruction of the eastern North China Craton.

  20. The tectonic evolution of Southern part of the Sao Francisco Craton

    International Nuclear Information System (INIS)

    Teixeira, W.

    1986-01-01

    The potentiality of geochronology when it is applied to the geologic context of craton basement of archean areas is shown. Samples from southern part of the Sao Francisco Craton, in Brazil, were collected for petrographic analysis and geochronological data interpretation. The set of radiometric determinations was obtained by K-Ar, Rb-Sr, Pb-Pb and U-Pb methods. (M.C.K.) [pt

  1. The Rae craton of Laurentia/Nuna: a tectonically unique entity providing critical insights into the concept of Precambrian supercontinental cyclicity

    Science.gov (United States)

    Bethune, K. M.

    2015-12-01

    Forming the nucleus of Laurentia/Nuna, the Rae craton contains rocks and structures ranging from Paleo/Mesoarchean to Mesoproterozoic in age and has long been known for a high degree of tectonic complexity. Recent work strongly supports the notion that the Rae developed independently from the Hearne; however, while the Hearne appears to have been affiliated with the Superior craton and related blocks of 'Superia', the genealogy of Rae is far less clear. A diagnostic feature of the Rae, setting it apart from both Hearne and Slave, is the high degree of late Neoarchean to early Paleoproterozoic reworking. Indeed, following a widespread 2.62-2.58 Ga granite bloom, the margins of Rae were subjected to seemingly continuous tectonism, with 2.55-2.50 Ga MacQuoid orogenesis in the east superseded by 2.50 to 2.28 Ga Arrowsmith orogenesis in the west. A recent wide-ranging survey of Hf isotopic ratios in detrital and magmatic zircons across Rae has demonstrated significant juvenile, subduction-related crustal production in this period. Following break-up at ca. 2.1 Ga, the Rae later became a tectonic aggregation point as the western and eastern margins transitioned back to convergent plate boundaries (Thelon-Taltson and Snowbird orogens) marking onset of the 2.0-1.8 Ga assembly of Nuna. The distinctive features of Rae, including orogenic imprints of MacQuoid and Arrowsmith vintage have now been identified in about two dozen cratonic blocks world-wide, substantiating the idea that the Rae cratonic family spawned from an independent earliest Paleoproterozoic landmass before its incorportation in Nuna. While critical tests remain to be made, including more reliable ground-truthing of proposed global correlations, these relationships strongly support the notion of supercontinental cyclicity in the Precambrian, including the Archean. They also challenge the idea of a globally quiescent period in the early Paleoproterozoic (2.45-2.2 Ga) in which plate tectonics slowed or shut down.

  2. Petrography and Geochemistry (Trace, Ree and Pge of Pedda Cherlo Palle Gabbro-Diorite Pluton, Prakasam Igneous Province, Andhra Pradesh, India

    Directory of Open Access Journals (Sweden)

    Subramanyam K.S.V.

    2015-09-01

    Full Text Available Prakasam Igneous Province (PIP is an important geological domain in the Eastern Dharwar Craton (EDC, found in the junction zone between the EDC and Eastern Ghat Mobile Belt (EGMB. The Pedda Cherlo Palle (PCP gabbros are massive, leucocratic-mesocractic, and show cumulus textures with minerals plagioclase, cpx, and amphiboles. Compositionally, plagioclase is a labradorite-bytownite, cpx is diopside to augite, olivines are hyalosiderites and amphiboles are magnesiohornblendes. PCP gabbros have normal SiO2, high Al2O3, moderate to high TiO2, Na2O and medium Fe2O3, so, classified as subalkaline tholeiitic gabbros. Fractionated rare earth element (REE patterns, high abundance of large ion lithofile elements (LILE and transitional metals coupled with light REE (LREE relative enrichment over heavy REE (HREE and Nb are characteristics of partial melting of depleted mantle and melts that have undergone fractional crystalisation. These partial melts are enriched in LREE and LILE, due to the addition of slab derived sediment and fluids. PCP gabbros contain low abundance (5.1 to 24.6 ng/g of platinum group elements (PGE, and show an increase in the order Ir>Os>Pt>Ru»Pd>Rh. We propose that the subduction related intraoceanic island arc might have accreted to the southeastern margin of India to the east of Cuddapah basin in a collisional regime that took place during Ur to Rodinia amalgamations.

  3. Cyclic Cratonic Carbonates and Phanerozoic Calcite Seas.

    Science.gov (United States)

    Wilkinson, Bruce H.

    1982-01-01

    Discusses causes of cyclicity in cratonic carbonate sequences and evidence for and potential significance of postulated primary calcite sediment components in past Paleozoic seas, outlining problems, focusing on models explaining existing data, and identifying background. Future sedimentary geologists will need to address these and related areas…

  4. On the origin of cratonic `high-mu' isotopic signatures

    Science.gov (United States)

    Reimink, J. R.; Carlson, R.; Shirey, S. B.; Pearson, D. G.; Kamber, B. S.

    2017-12-01

    Some Archean cratons (i.e. Slave, Wyoming) contain Neoarchean granitoids with initial Pb isotopic compositions indicative of derivation from sources characterized by high time-integrated U/Pb ratios (high-mu [1]). Single-stage high-m precursor source reservoir separation from the depleted mantle occurred no later than 3.9 Ga [2]. However, multi-stage separation could have occurred in the Hadean, suggesting that recycling or reworking of Eoarchean/Hadean crust played a significant role in the generation of Neoarchean granitic crust in many cratons. The Sm-Nd system is similar to the U-Pb system in that it has a short-lived parent-daughter pair (146Sm-142Nd) that is sensitive to very early differentiation events, as well as a long-lived parent-daughter pair (147Sm-143Nd) that is sensitive to differentiation throughout all of Earth history. The 103 Ma half-life of 146Sm makes it sensitive only to Sm/Nd fractionation that occurred in the Hadean, providing a useful tracker for very early differentiation events. Indeed, evidence for Neoarchean remelting of ancient crust in another craton has come from analyses of the paired Sm-Nd isotope systems from the Hudson Bay terrane of the northeastern Superior Province. These results indicate that the source of 2.7 Ga Hudson Bay terrane granitoids was Hadean mafic crust, and not Eoarchean felsic crust [3]. Here, we present new data from Neoarchean granites located in the Slave and Wyoming cratons, along with modeling of the dual paired-isotope systems of U-Pb and Sm-Nd to achieve a tighter constraint on the composition of the precursors and the timing of their melting. Combining our newly collected 142Nd data with the high-m signature of these Neoarchean rocks, we evaluate precursor source separation ages along with the source Sm/Nd and U/Pb compositions. In the simplest end-member scenarios, use of the 142Nd system allows us to test whether the cratonic high-mu signature was created by melting of Hadean mafic crust or Eoarchean

  5. Western cratonic domain in Uruguay: geochronology

    International Nuclear Information System (INIS)

    Preciozzi, F.; Peel, F.; Muzio, R.; Ledesma, J.; Guerequiz, R.

    2009-01-01

    In this article has been studied the Western cratonic in Uruguay are divided into three major units: Piedra Alta Terrane, Valentines Block and Pavas Terrane. Piedra Alta Terrane has of evidence of Neo proterozoic orogenesis . Sarandi del Yi -Arroyo Solis Grande shear zone separate, it from Valentine block . Valentine Block separate it from Pavas terrane by Cueva del Tigre shear zone

  6. Saghro Group in the Ougnat Massif (Morocco), an evidence for a continuous Cadomian basin along the northern West African Craton

    Science.gov (United States)

    Michard, André; Soulaimani, Abderrahmane; Ouanaimi, Hassan; Raddi, Youssef; Aït Brahim, Lahsen; Rjimati, Ech-Cherki; Baidder, Lahssen; Saddiqi, Omar

    2017-03-01

    The Saghro Group (SG) is a folded, low-grade volcano-sedimentary series up to 8 km thick that crops out within and to the north of the Pan-African suture zone in the central and eastern Anti-Atlas. Here we describe the SG of the Ougnat inliers that are exposed in the easternmost Anti-Atlas beneath the unconformable, Late Ediacaran Ouarzazate Group (OZG) volcanic rocks. The Ougnat SG mostly consists of volcaniclastic greywackes accumulated in a peritidal-to-shallow basin. The basin infilling was deformed by NNE-trending, mostly upright folds with axial-planar slaty cleavage and low-grade metamorphism. The deformed SG rocks were intruded by the ∼550 Ma Mellab hypovolcanic granodiorite. The latter also crosscuts the lowest OZG rocks that are dated to 574-571 Ma in the western Saghro region. The SG rocks that form the Siroua and Saghro inliers have an oldest age of 620-610 Ma and were folded at ∼610-580 Ma at the onset of the Cadomian orogenic events. We show that the SG rocks are similar to the ;Série verte; (SV) rocks that are exposed in the Ougarta and western Hoggar east of the Pan-African suture. We infer that the SG and SV rocks accumulated in a same, continuous basin that was bounding the West African Craton to the north and the east. This strongly subsiding basin formed close to a volcanic arc and was folded during the last Pan-African synmetamorphic events. Fold orientation and age of folding differ however along the edge of the West African Craton. The orogenic greywackes that form the remnants of the SG-SV basin thus constitute a precious record of the diachronic Cadomian event s.l. along the West African Craton northern margin.

  7. Plume-induced dynamic instabilities near cratonic blocks: Implications for P-T-t paths and metallogeny

    NARCIS (Netherlands)

    Guillou-Frottier, L.; Burov, E.; Cloetingh, S.; Le Goff, E.; Deschamps, Y.; Huet, B.; Bouchot, V.

    2012-01-01

    Plume head - lithosphere interactions around cratonic blocks result in thermo-mechanical disturbances that lead to heating and burial phases of crustal rocks. We present results from numerical models of plume head - cratonic blocks interactions where a free upper surface condition and realistic

  8. Paleomagnetic study of 1765 Ma dyke swarm from the Singhbhum Craton: Implications to the paleogeography of India

    Science.gov (United States)

    Shankar, Ravi; Srinivasa Sarma, D.; Ramesh Babu, N.; Parashuramulu, V.

    2018-05-01

    We report the first key paleopole as a result of paleomagnetic study on a precisely dated 1765.3 ± 1.0 Ma WNW-ESE trending dyke swarm from Singhbhum Craton. This pole has been used in this study to propose the paleogeographic reconstruction of India with Baltica Craton and North China Craton. Incremental alternating field (AF) and thermal demagnetization, isolated high coercivity components with north to north-westerly declination and shallow negative inclination from 9 sampling sites which are representing different individual dykes. The primary origin of the ChRM is supported by the positive baked contact test. The WNW-ESE trending dykes yield a mean paleomagnetic direction with a declination = 329.2° and an inclination = -22.8° (k = 31.6; α95 = 9.3°). The positive bake contact test proves the primary nature of remanence. The pole position of Singhbhum Craton at 1765 Ma is 45°N, 311°E (dp = 5.2 and dm = 9.9). Paleogeographic reconstruction at ca. 1770 Ma, supported by geological, tectonic and metallogenic evidences indicate that the Baltica Craton and India linkage can be stable for at least ∼370 Ma (∼1770-1400 Ma). There is also reasonable evidence in support of India-North China Craton spatial proximity at ∼1770 Ma.

  9. Geology of the Terre Adélie Craton (135 – 146˚ E)

    Science.gov (United States)

    Ménot, R.P.; Duclaux, G.; Peucat, J.J.; Rolland, Y.; Guillot, S.; Fanning, M.; Bascou, J.; Gapais, D.; Pêcher, A.

    2007-01-01

    More than 15 years of field and laboratory investigations on samples from Terre Adélie to the western part of George Vth Land (135 to 146°E) during the GEOLETA program allow a reassessment of the Terre Adélie Craton (TAC) geology. The TAC represents the largest exposed fragment of the East Antarctic Shield preserved from both Grenville and Ross tectono-metamorphic events. Therefore it corresponds to a well-preserved continental segment that developed from the Neoarchean to the Paleoproterozoic. Together with the Gawler Craton in South Australia, the TAC is considered as part of the Mawson continent, i.e. a striking piece of the Rodinia Supercontinent. However, this craton represents one of the less studied parts of the East Antarctic Shield. The three maps presented here clearly point out the extent of two distinct domains within the Terre Adélie Craton and suggest that the TAC was built up through a polyphased evolution during the Neoarchean-Siderian (c.a. 2.5Ga) and the Statherian (c.a. 1.7Ga) periods. These data support a complete re-assessment of the TAC geology and represent a valuable base for the understanding of global geodynamics changes during Paleoproterozoic times.

  10. The geotectonic evolution of southern part of Sao Francisco Craton, based in geochronologic interpretation

    International Nuclear Information System (INIS)

    Teixeira, W.

    1985-01-01

    Interpretation of available radiometric data from poly metamorphic terranes of southern part of the Sao Francisco Craton demonstrates the importance of geochronology as a tool in the study of ancient crustal evolution. In addition, radiometric study of basic intrusive magmatism helps define the most important epochs of crustal rifting during the Proterozoic. The definition of the southern border of the cratonic area based on distinctive age patterns of the geochronological provinces is also discussed. Finally, the geochronologic evolution of the Bambui platform cover is presented. Approximately 250 radiometric age determinations (Rb-Sr, K-Ar and Pb-Pb methods) were interpreted principally through the use of iso chronic diagrams. The geologic history tectonomagnetic events identified in this study is compared to the crustal evolution of similar segments of the Sao Francisco Craton and elsewhere. (author)

  11. Craton-derived alluvium as a major sediment source in the Himalayan Foreland Basin of India

    DEFF Research Database (Denmark)

    Sinha, R.; Kettanah, Y.; Gibling, M.R.

    2009-01-01

    of the Bundelkhand Complex. Along the Yamuna Valley the red alluvium is overlain by gray alluvium dated at 82–35 ka ago, which also yields a cratonic signature, with large amounts of smectite derived from the Deccan Traps. Cratonic contributions are evident in alluvium as young as 9 ka ago in a section 25 km north...

  12. Paleozoic–Mesozoic Porphyry Cu(Mo and Mo(Cu Deposits within the Southern Margin of the Siberian Craton: Geochemistry, Geochronology, and Petrogenesis (a Review

    Directory of Open Access Journals (Sweden)

    Anita N. Berzina

    2016-11-01

    Full Text Available The southern margin of the Siberian craton hosts numerous Cu(Mo and Mo(Cu porphyry deposits. This review provides the first comprehensive set of geological characteristics, geochronological data, petrochemistry, and Sr–Nd isotopic data of representative porphyry Cu(Mo and Mo(Cu deposits within the southern margin of the Siberian craton and discusses the igneous processes that controlled the evolution of these magmatic systems related to mineralization. Geochronological data show that these porphyry deposits have an eastward-younging trend evolving from the Early Paleozoic to Middle Mesozoic. The western part of the area (Altay-Sayan segment hosts porphyry Cu and Mo–Cu deposits that generally formed in the Early Paleozoic time, whereas porphyry Cu–Mo deposits in the central part (Northern Mongolia formed in the Late Paleozoic–Early Mesozoic. The geodynamic setting of the region during these mineralizing events is consistent with Early Paleozoic subduction of Paleo-Asian Ocean plate with the continuous accretion of oceanic components to the Siberian continent and Late Paleozoic–Early Mesozoic subduction of the west gulf of the Mongol–Okhotsk Ocean under the Siberian continent. The eastern part of the study area (Eastern Transbaikalia hosts molybdenum-dominated Mo and Mo–Cu porphyry deposits that formed in the Jurassic. The regional geodynamic setting during this mineralizing process is related to the collision of the Siberian and North China–Mongolia continents during the closure of the central part of the Mongol–Okhotsk Ocean in the Jurassic. Available isotopic data show that the magmas related to porphyritic Cu–Mo and Mo–Cu mineralization during the Early Paleozoic and Late Paleozoic–Early Mesozoic were mainly derived from mantle materials. The generation of fertile melts, related to porphyritic Mo and Mo–Cu mineralization during the Jurassic involved variable amounts of metasomatized mantle source component, the

  13. Crustal structure of the Siberian craton and the West Siberian basin

    DEFF Research Database (Denmark)

    Cherepanova, Yulia; Artemieva, Irina; Thybo, Hans

    2013-01-01

    We present a digital model SibCrust of the crustal structure of the Siberian craton (SC) and the West Siberian basin (WSB), based on all seismic profiles published since 1960 and sampled with a nominal interval of 50. km. Data quality is assessed and quantitatively assigned to each profile based...... and ~. 6.2-6.6. km/s in parts of the WSB and SC. Exceptionally high basement Vp velocities (6.8-7.0. km/s) at the northern border between the SC and the WSB indicate the presence of magmatic intrusions and are proposed to mark the source zone of the Siberian LIP. The cratonic crust generally consists...

  14. Mesoproterozoic evolution of the Rio de la Plata Craton in Uruguay: at the heart of Rodinia?

    DEFF Research Database (Denmark)

    Gaucher, Claudio; Frei, Robert; Chemale, Farid

    2011-01-01

    Mesoproterozoic volcanosedimentary units and tectonic events occurring in the Ri´o de la Plata Craton (RPC) are reviewed. A belt consisting of volcanosedimentary successions exhibiting greenschist-facies metamorphism is exposed in the eastern RPC (Nico Pe´rez Terrane) in Uruguay. The Parque UTE...... and top, and Conophyton-bearing limestones and massive dolostones in the middle. A U–Pb LA-ICP MS zircon age of 1,433 ± 6 Ma is reported here for lapilli-tuffs at the base of the Mina Verdu´n Group (Cerro de las Vi´boras Formation). This age shows that the Mina Verdu´n Group immediately postdates...... the Sarandi´ del Yi´ megashear. We report a U–Pb LA-ICP MS zircon age (upper intercept) of 3,096 ± 45 Ma for metatonalites of the La China Complex (Nico Pe´rez Terrane), which yield a lower intercept age of 1,252 Ma. A proto-Andean, Mesoproterozoic belt is envisaged to account for abundant Mesoproterozoic...

  15. Lateral heterogeneity and vertical stratification of cratonic lithospheric keels: a case study of the Siberian craton

    DEFF Research Database (Denmark)

    Artemieva, Irina; Cherepanova, Yulia; Herceg, Matija

    2014-01-01

    by regional xenolith P-T arrays,lithosphere density heterogeneity as constrained by free-board and satellite gravity data, and the non-thermalpart of upper mantle seismic velocity heterogeneity based on joint analysis of thermal and seismic tomography data.Density structure of the cratonic lithosphere...... and strongly depleted lithospheric mantle of the Archean nuclei, particularly below the Anabar shield.Since we cannot identify the depth distribution of density anomalies, we complement the approach by seismicdata. An analysis of temperature-corrected seismic velocity structure indicates strong vertical...

  16. K-Ar geochronology of mafic dyke swarms from the meridional part of Sao Francisco craton and implications on tectonic context

    International Nuclear Information System (INIS)

    Teixeira, W.; Kawashita, K.; Pecchio, M.; Tame, N.R.

    1988-01-01

    The southern region of the Sao Francisco Craton is made up of gneissic-granitoid terranes (mainly of amphibolite facies) associated with supracrustals, which can be separed into two crustal provinces, the oldest formed during the Archean (3-2-2.6 Ga.), and the youngest in the Early Proterozoic (2.4-2.0 Ga.). Mafic dyke swarms inject the basement complexes in the area west of Belo Horizonte city, but not the Late proterozoic Bambui sedimentary cover. These dykes show NNW, NW, WNW, NNE and ENE trends and are of anorogenic character. Most dykes are tholeiitic in composition. Metamorphic recrystallization at greenschist to amphibolite facies as well as minor hidrothermal and/or deuteric transformations are characteristics in the majority of the these dykes. About sixty K/Ar determinations have been performed on plagioclases, amphiboles and whole rocks. They are interpretated combining the use of K/Ar diagrams and histogram, and according to the crustal evolution proposed for the craton. The available radiometric data suggest that the main period of mafic intrusions took place in the Early proterozoic as supported by the apparent ages on amphiboles. However, the beginning of the Middle Proterozoic (1.7-1.5 Ga.) probably corresponds to a period of tensional tectonics as well. On the other hand, most ages obtained on plagioclases and whole rocks, can be associated with Late Proterozoic processes of argon gain or loss. The results are tectonicaly associated with crustal rifting of the continental mass. This two radiometric groupings are characteristic for the evolution of the Early proterozoic crustal provine and of the Mid-Proterozoic intracratonic Espinhaco System respectively. The youngest Late Proterozoic apparent ages associated with the reflections of the contemporaneous evolution of the Braziliano marginal mobile belt which is also suggested by the partial resetting of the K/Ar ages of basement rocks within the eastern part of the Sao Francisco Craton. (author) [pt

  17. High-quality heat flow determination from the crystalline basement of the south-east margin of North China Craton

    Science.gov (United States)

    Jiang, Guangzheng; Tang, Xiaoyin; Rao, Song; Gao, Peng; Zhang, Linyou; Zhao, Ping; Hu, Shengbiao

    2016-03-01

    Very few of heat flow data have come from the crystalline basement in the North China Craton but rather from boreholes in the sedimentary cover of oil-gas basins. Explorations for hot dry rock (HDR) geothermal resources and porphyry gold deposits in eastern China offer now valuable opportunities to study the terrestrial heat flow in the crystalline basement. In this study, we obtained continuous temperature logs from two boreholes (the LZ borehole with a depth of 3471 m and the DR borehole with a depth of 2179 m) located in the south-east margin of the North China Craton. The boreholes have experienced long shut-in times (442 days and 261 days for the LZ borehole and DR borehole, respectively); thus, it can be expected that the temperature conditions have re-equilibrated after drilling and drill-mud circulation. Rock thermal conductivity and radiogenic heat production were measured for 68 crystalline rock samples from these two boreholes. The measured heat-flow density was determined to be 71.8 ± 2.3 mW m-2 (for the LZ borehole) and 91.5 ± 1.2 mW m-2 (for the DR borehole). The heat flow for the LZ borehole is close to the value of 75 mW m-2 determined in the Chinese Continental Scientific Drilling main hole (CCSD MH), both being in the Sulu-Dabie orogenic belt and thus able to verify each other. The value for the DR borehole is higher than the above two values, which supports former high heat-flow values determined in the Bohai Bay Basin.

  18. Updating the Geologic Barcodes for South China: Discovery of Late Archean Banded Iron Formations in the Yangtze Craton.

    Science.gov (United States)

    Ye, Hui; Wu, Chang-Zhi; Yang, Tao; Santosh, M; Yao, Xi-Zhu; Gao, Bing-Fei; Wang, Xiao-Lei; Li, Weiqiang

    2017-11-08

    Banded iron formations (BIFs) in Archean cratons provide important "geologic barcodes" for the global correlation of Precambrian sedimentary records. Here we report the first finding of late Archean BIFs from the Yangtze Craton, one of largest Precambrian blocks in East Asia with an evolutionary history of over 3.3 Ga. The Yingshan iron deposit at the northeastern margin of the Yangtze Craton, displays typical features of BIF, including: (i) alternating Si-rich and Fe-rich bands at sub-mm to meter scales; (ii) high SiO 2  + Fe 2 O 3total contents (average 90.6 wt.%) and Fe/Ti ratios (average 489); (iii) relative enrichment of heavy rare earth elements and positive Eu anomalies (average 1.42); (iv) and sedimentary Fe isotope compositions (δ 56 Fe IRMM-014 as low as -0.36‰). The depositional age of the BIF is constrained at ~2464 ± 24 Ma based on U-Pb dating of zircon grains from a migmatite sample of a volcanic protolith that conformably overlied the Yingshan BIF. The BIF was intruded by Neoproterozoic (805.9 ± 4.7 Ma) granitoids that are unique in the Yangtze Craton but absent in the North China Craton to the north. The discovery of the Yingshan BIF provides new constraints for the tectonic evolution of the Yangtze Craton and has important implications in the reconstruction of Pre-Nuna/Columbia supercontinent configurations.

  19. New Constraints on Upper Mantle Structure Underlying the Diamondiferous Central Slave Craton, Canada, from Teleseismic Body Wave Tomography

    Science.gov (United States)

    Esteve, C.; Schaeffer, A. J.; Audet, P.

    2017-12-01

    Over the past number of decades, the Slave Craton (Canada) has been extensively studied for its diamondiferous kimberlites. Not only are diamonds a valuable resource, but their kimberlitic host rocks provide an otherwise unique direct source of information on the deep upper mantle (and potentially transition zone). Many of the Canadian Diamond mines are located within the Slave Craton. As a result of the propensity for diamondiferous kimberlites, it is imperative to probe the deep mantle structure beneath the Slave Craton. This work is further motivated by the increase in high-quality broadband seismic data across the Northern Canadian Cordillera over the past decade. To this end we have generated a P and S body wave tomography model of the Slave Craton and its surroundings. Furthermore, tomographic inversion techniques are growing ever more capable of producing high resolution Earth models which capture detailed structure and dynamics across a range of scale lengths. Here, we present preliminary results on the structure of the upper mantle underlying the Slave Craton. These results are generated using data from eight different seismic networks such as the Canadian National Seismic Network (CNSN), Yukon Northwest Seismic Network (YNSN), older Portable Observatories for Lithospheric Analysis and Reseach Investigating Seismicity (POLARIS), Regional Alberta Observatory for Earthquake Studies Network (RV), USArray Transportable Array (TA), older Canadian Northwest Experiment (CANOE), Batholith Broadband (XY) and the Yukon Observatory (YO). This regional model brings new insights about the upper mantle structure beneath the Slave Craton, Canada.

  20. Mg-Fe Isotope Systems of Mantle Xenoliths: Constrains on the Evolution of Siberian Craton

    Science.gov (United States)

    An, Y.; Kiseeva, E. S.; Sobolev, N. V.; Zhang, Z.

    2017-12-01

    Mantle xenoliths bring to the surface a variety of lithologies (dunites, lherzolites, harzburgites, wehrlites, eclogites, pyroxenites, and websterites) and represent snapshots of the geochemical processes that occur deep within the Earth. Recent improvements in the precision of the MC-ICP-MS measurements have allowed us to expand the amount of data on Mg and Fe isotopes for mantle-derived samples. For instance, to constrain the isotopic composition of the Earth based on the study of spinel and garnet peridotites (An et al., 2017; Teng et al., 2010), to trace the origin and to investigate the isotopic fractionation mechanism during metamorphic process using cratonic or orogenic eclogites (Li et al., 2011; Wang et al., 2012) and to reveal the metasomatism-induced mantle heterogeneity by pyroxenites (Hu et al., 2016). Numerous multi-stage modification events and mantle layering are detected in the subcontinental lithospheric mantle under the Siberian craton (Ashchepkov et al., 2008a; Sobolev et al., 1975, etc). Combined analyses of Mg and Fe isotopic systems could provide new constraints on the formation and evolution of the ancient cratonic mantle. In order to better constrain the magnitude and mechanism of inter-mineral Mg and Fe isotopic fractionations at high temperatures, systematic studies of mantle xenoliths are needed. For example, theoretical calculations and natural samples measurements have shown that large equilibrium Mg isotope fractionations controlled by the difference in coordination number of Mg among minerals could exist (Huang et al., 2013; Li et al., 2011). Thus, the Mg isotope geothermometer could help us trace the evolution history of ancient cratons. In this study we present Mg and Fe isotopic data for whole rocks and separated minerals (clinopyroxene (cpx) and garnet (grt)) from different types of mantle xenoliths (garnet pyroxenites, eclogites, grospydites and garnet peridotites) from a number of kimberlite pipes in Siberian craton (Udachnaya

  1. Geochemistry and geochronology of the Archean and palaeo-Proterozoic formations of southern Cameroon (Ntem group, Congo craton)

    International Nuclear Information System (INIS)

    Rchameni, R.

    1997-01-01

    The aim of this work is to understand the crustal evolution of the NW margin of the Congo craton using structural, petrography, isotopic, geochemical and geochronological studies of the Archean and palaeo-Proterozoic formations of the Ntem group of southern Cameroon. The synthesis of these studies allows to propose a diapir-type gravity model linked with the genesis of granitoids to explain the geodynamical evolution of this part of the craton during the Archean. A convergence model with the collision of the Congo and Sao-Francisco cratons and with crust thickening followed by a relaxation phase is proposed for the palaeo-Proterozoic. (J.S.)

  2. Geochronology of sedimentary and metasedimentary Precambrian rocks of the West African craton

    International Nuclear Information System (INIS)

    Clauer, N.; Jeannette, D.; Trompette, R.

    1982-01-01

    This contribution summarizes current knowledge of the geochronology of the Upper Proterozoic sedimentary rocks covering the West African craton. This was done by using direct dating methods. Correlations between the northern edge of the Tindouf basin and the northern and southern part of the Taoudeni basin, as well as the Volta basin, are proposed. Tectonic, volcanic and thermal activities in connection with the Pan-African orogeny are recorded only around the craton. They induced either sedimentation lacks in Morocco or sedimentation excesses in Hoggar. Unsolved problems such as the precise stratigraphic position of the uppermost Proterozoic tillitic episode and the correlation within the Moroccan Anti-Atlas are also raised. (Auth.)

  3. Compositional trends among Kaapvaal Craton garnet peridotite xenoliths and their effects on seismic velocity and density

    DEFF Research Database (Denmark)

    Schutt, Derek; Lesher, Charles

    2010-01-01

    garnet and clinopyroxene enrichment. Using the parameterization of Schutt and Lesher (2006) we show that at cratonic mantle temperatures and pressures, orthopyroxene enrichment results in little change in bulk density (ρbulk) and shear-wave velocity (VS), but decreases compressional wave velocities (VP......We examine the modes and compositions of garnet-bearing peridotite xenoliths from the Kaapvaal Craton to quantify factors governing density and seismic velocity variations within metasomatically altered cratonic mantle. Three distinct compositional trends are resolved by principal component...... analysis. The first reflects differences in residue composition resulting from partial melting. The second is associated with orthopyroxene (opx) enrichment, possibly due to silica addition by subduction zone fluids in the source region of the xenoliths. The third principal component reflects garnet...

  4. Lithospheric structure of the Northern Ordos and adjacent regions from surface wave tomography: implications to the tectonics of the North China Craton

    Science.gov (United States)

    LI, S.; Guo, Z.; Chen, Y. J.

    2017-12-01

    We present a high-resolution upper mantle S velocity model of the northern Ordos block using ambient noise tomography and two-plane-wave tomography between 8 and 143 s. The Ordos block, regarded as the nuclei of the Archean craton of North China Craton, is underlain by high velocity down to 200 km, indicating the preservation of cratonic root at the interior. However, thick lithospheric keel (≥ 200 km) is not observed outside the Ordos, suggesting craton reworking around the Ordos. The most important findings is the prominent low velocity shown beneath the Datong volcano that migrates westward with depth. At 200 km depth, the low velocity locates almost 500 km west to the leading edge of the flat-lying Pacific slab in the mantle transition zone. This observation is in conflict with the previous interpretation that the Datong volcano is fed by the deep upwelling related to the subduction of the Pacific plate. The westward tilted low velocity beneath the Datong volcano, however, is in agreement with the predominant NW-SE trending alignment of fast direction revealed by SKS splitting in this area, suggesting the Datong volcano is likely due to the asthenospheric mantle flow from west. Two possible scenarios could be related to this mantle process. First, the low velocity beneath the Datong volcano may link to the large-scale, deep-rooted mantle upwelling beneath the Mongolia, northwest to the Datong volcano at deeper depth revealed by Zhang et al. (2016). We postulate that when the raising mantle materials reaches the shallow depth, it would be forced bent by the thick lithosphere beneath the Gobi in Mongolia and flow southeastward to Datong volcano. Second, it is also worth noting that the low velocity beneath the Datong volcano connects to the low velocity zone (LVZ) beneath the Ordos block below 200km, which further links the LVZ beneath the northeastern Tibet to the west. Therefore, the Datong volcano could be fed by the mantle flow from northeastern Tibet. The

  5. Seismic Structure of Southern African Cratons

    DEFF Research Database (Denmark)

    Soliman, Mohammad Youssof Ahmad; Artemieva, Irina; Levander, Alan

    2014-01-01

    functions and finite-frequency tomography based on data from the South Africa Seismic Experiment (SASE). Combining the two methods provides high vertical and lateral resolution. The main results obtained are (1) the presence of a highly heterogeneous crustal structure, in terms of thickness, composition (as......Cratons are extremely stable continental crustal areas above thick depleted lithosphere. These regions have remained largely unchanged for more than 2.5 Ga. This study presents a new seismic model of the seismic structure of the crust and lithospheric mantle constrained by seismic receiver...

  6. Seismic imaging of Southern African cratons

    DEFF Research Database (Denmark)

    Soliman, Mohammad Youssof Ahmad

    Cratonic regions are the oldest stable parts of continents that hold most of Earth’s mineral resources. There are several open questions regarding their formation and evolution. In this PhD study, passive source seismic methods have been used to investigate the crustal and lithosphere structures...... of this research was based on Ps- and Sp- receiver functions analysis to determine crustal thickness while finite-frequency traveltime tomography is utilized to model 3D heterogeneity in the upper mantle. Combining the two methods provides high vertical and lateral resolution....

  7. Fluid inclusion study of radioactive granite and cherty cataclasite in the Southeastern part of Nanded district, Maharashtra: implications for the uranium mineralisation

    International Nuclear Information System (INIS)

    Banerjee, Rahul; Shivkumar, K.; Thomas, Tresa; Thomas, Jugina; Pandian, M.S.

    2013-01-01

    Southeastern part of Nanded district, Maharashtra exposes Palaeoproterozoic granitoids, representing the younger phase of Peninsular Gneissic Complex (PGC), mark the northeastern extension of Eastern Dharwar Craton. These granitoids are predominantly pink/grey granites, which are traversed by younger phosphatic cherty cataclasites close to the Deccan Trap capping. They are also affected by profuse pegmatitic/quartzo-feldspathic, quartz and epidote venations, especially close to fault/shear zones. A number of N-S to NNE-SSW, NE-SW, NW-SE and E-W trending lineaments marked by faults/fractures/shear zones and dykes are delineated in this granitic terrain. Among these, NE-SW and NNE-SSW faults/shear zones affecting granitoids and cherty cataclasites in Shahpur-Sujayatpur and Thadisaoli area have recorded significant uranium anomalies (Granitoids: upto 1% U 3 O 8 and 0.20% ThO 2 ; Cherty cataclasites upto 0.11% U 3 O 8 and <0.005% ThO 2 ) and enrichment in rare metal and rare earth element content (Nb-77ppm, Y-111 ppm, Zr-432ppm; n=9 and total REE-1167ppm; n=3). Presence of discrete uranium/thorium minerals (uraninite, b-uranophane and thorite) and high content of resistates viz., apatite, zircon, allanite, sphene, cerianite, monazite and ilmenite are responsible for radioactivity in granitoids while phosphatic material accounts for radioactivity in cherty cataclasites

  8. The geological record of base metal sulfides in the cratonic mantle: A microscale 187Os/188Os study of peridotite xenoliths from Somerset Island, Rae Craton (Canada)

    Science.gov (United States)

    Bragagni, A.; Luguet, A.; Fonseca, R. O. C.; Pearson, D. G.; Lorand, J.-P.; Nowell, G. M.; Kjarsgaard, B. A.

    2017-11-01

    We report detailed petrographic investigations along with 187Os/188Os data in Base Metal Sulfide (BMS) on four cratonic mantle xenoliths from Somerset Island (Rae Craton, Canada). The results shed light on the processes affecting the Re-Os systematics and provide time constraints on the formation and evolution of the cratonic lithospheric mantle beneath the Rae craton. When devoid of alteration, BMS grains mainly consist of pentlandite + pyrrhotite ± chalcopyrite. The relatively high BMS modal abundance of the four investigated xenoliths cannot be reconciled with the residual nature of these peridotites, but requires addition of metasomatic BMS. This is especially evident in the two peridotites with the highest bulk Pd/Ir and Pd/Pt. Metasomatic BMS likely formed during melt/fluid percolation in the Sub Continental Lithospheric Mantle (SCLM) as well as during infiltration of the host kimberlite magma, when djerfisherite crystallized around older Fe-Ni-sulfides. On the whole-rock scale, kimberlite metasomatism is visible in a subset of bulk xenoliths, which defines a Re-Os errorchron that dates the host magma emplacement. The 187Os/188Os measured in the twenty analysed BMS grains vary from 0.1084 to >0.17 and it shows no systematic variation depending on the sulfide mineralogical assemblage. The largest range in 187Os/188Os is observed in BMS grains from the two xenoliths with the highest Pd/Ir, Pd/Pt, and sulfide modal abundance. The whole-rock TRD ages of these two samples underestimate the melting age obtained from BMS, demonstrating that bulk Re-Os model ages from peridotites with clear evidence of metasomatism should be treated with caution. The TRD ages determined in BMS grains are clustered around 2.8-2.7, ∼2.2 and ∼1.9 Ga. The 2.8-2.7 Ga TRD ages document the main SCLM building event in the Rae craton, which is likely related to the formation of the local greenstone belts in a continental rift setting. The Paleoproterozoic TRD ages can be explained by

  9. Moho Depth Variations in the Northeastern North China Craton Revealed by Receiver Function Imaging

    Science.gov (United States)

    Zhang, P.; Chen, L.; Yao, H.; Fang, L.

    2016-12-01

    The North China Craton (NCC), one of the oldest cratons in the world, has attracted wide attention in Earth Science for decades because of the unusual Mesozoic destruction of its cratonic lithosphere. Understanding the deep processes and mechanism of this craton destruction demands detailed knowledge about the deep structure of the region. In this study, we used two-year teleseismic receiver function data from the North China Seismic Array consisting of 200 broadband stations deployed in the northeastern NCC to image the Moho undulation of the region. A 2-D wave equation-based poststack depth migration method was employed to construct the structural images along 19 profiles, and a pseudo 3D crustal velocity model of the region based on previous ambient noise tomography and receiver function study was adopted in the migration. We considered both the Ps and PpPs phases, but in some cases we also conducted PpSs+PsPs migration using different back azimuth ranges of the data, and calculated the travel times of all the considered phases to constrain the Moho depths. By combining the structure images along the 19 profiles, we got a high-resolution Moho depth map beneath the northeastern NCC. Our results broadly consist with the results of previous active source studies [http://www.craton.cn/data], and show a good correlation of the Moho depths with geological and tectonic features. Generally, the Moho depths are distinctly different on the opposite sides of the North-South Gravity Lineament. The Moho in the west are deeper than 40 km and shows a rapid uplift from 40 km to 30 km beneath the Taihang Mountain Range in the middle. To the east in the Bohai Bay Basin, the Moho further shallows to 30-26 km depth and undulates by 3 km, coinciding well with the depressions and uplifts inside the basin. The Moho depth beneath the Yin-Yan Mountains in the north gradually decreases from 42 km in the west to 25 km in the east, varying much smoother than that to the south.

  10. Magnetotelluric investigations of the lithosphere beneath the central Rae craton, mainland Nunavut, Canada

    Science.gov (United States)

    Spratt, Jessica E.; Skulski, Thomas; Craven, James A.; Jones, Alan G.; Snyder, David B.; Kiyan, Duygu

    2014-03-01

    New magnetotelluric soundings at 64 locations throughout the central Rae craton on mainland Nunavut constrain 2-D resistivity models of the crust and lithospheric mantle beneath three regional transects. Responses determined from colocated broadband and long-period magnetotelluric recording instruments enabled resistivity imaging to depths of > 300 km. Strike analysis and distortion decomposition on all data reveal a regional trend of 45-53°, but locally the geoelectric strike angle varies laterally and with depth. The 2-D models reveal a resistive upper crust to depths of 15-35 km that is underlain by a conductive layer that appears to be discontinuous at or near major mapped geological boundaries. Surface projections of the conductive layer coincide with areas of high grade, Archean metasedimentary rocks. Tectonic burial of these rocks and thickening of the crust occurred during the Paleoproterozoic Arrowsmith (2.3 Ga) and Trans-Hudson orogenies (1.85 Ga). Overall, the uppermost mantle of the Rae craton shows resistivity values that range from 3000 Ω m in the northeast (beneath Baffin Island and the Melville Peninsula) to 10,000 Ω m beneath the central Rae craton, to >50,000 Ω m in the south near the Hearne Domain. Near-vertical zones of reduced resistivity are identified within the uppermost mantle lithosphere that may be related to areas affected by mantle melt or metasomatism associated with emplacement of Hudsonian granites. A regional decrease in resistivities to values of 500 Ω m at depths of 180-220 km, increasing to 300 km near the southern margin of the Rae craton, is interpreted as the lithosphere-asthenosphere boundary.

  11. Long-lived melting of ancient lower crust of the North China Craton in response to paleo-Pacific plate subduction, recorded by adakitic rhyolite

    Science.gov (United States)

    Wang, Chao; Song, Shuguang; Niu, Yaoling; Allen, Mark B.; Su, Li; Wei, Chunjing; Zhang, Guibin; Fu, Bin

    2017-11-01

    Magmatism in eastern China in response to paleo-Pacific plate subduction during the Mesozoic was complex, and it is unclear how and when exactly the magmas formed via thinning and partial destruction of the continental lithosphere. To better understand this magmatism, we report the results of a geochronological and geochemical study of Early Cretaceous adakitic rhyolite (erupted at 125.4 ± 2.2 Ma) in the Xintaimen area within the eastern North China Craton (NCC). In situ zircon U-Pb dating shows that this adakitic rhyolite records a long ( 70 Myrs) and complicated period of magmatism with concordant 206Pb/238U ages from 193 Ma to 117 Ma. The enriched bulk rock Sr-Nd isotopic compositions of the Xintaimen adakitic rhyolite, as well as the enriched zircon Hf and O isotopic compositions, indicate that the magmas parental to the adakitic rhyolite were derived from partial melting of the Paleoproterozoic mafic lower crust, heated by mafic melts derived from the mantle during the paleo-Pacific plate subduction. A minor older basement component is indicated by the presence of captured Neoarchean to Early Paleoproterozoic zircons. The Mesozoic zircons have restricted Hf and O isotopic compositions irrespective of their ages, suggesting that they formed from similar sources at similar melting conditions. The Xintaimen adakitic rhyolite offers an independent line of evidence that the ancient lower crust of eastern China underwent a long period ( 70 Myrs) of destruction, melting or remelting, from 193 to 120 Ma, related to the subduction of the paleo-Pacific plate beneath eastern China.

  12. Small-scale convection at a continental back-arc to craton transition: Application to the southern Canadian Cordillera

    Science.gov (United States)

    Hardebol, N. J.; Pysklywec, R. N.; Stephenson, R.

    2012-01-01

    A step in the depth of the lithosphere base, associated with lateral variations in the upper mantle temperature structure, can trigger mantle flow that is referred to as edge-driven convection. This paper aims at outlining the implications of such edge-driven flow at a lateral temperature transition from a hot and thin to a cold and thick lithosphere of a continental back-arc. This configuration finds application in the southern Canadian Cordillera, where a hot and thin back-arc is adjacent to the cold and thick North American Craton. A series of geodynamical models tested the thermodynamical behavior of the lithosphere and upper mantle induced by a step in lithosphere thickness. The mantle flow patterns, thickness and heat flow evolution of the lithosphere, and surface topography are examined. We find that the lateral temperature transition shifts cratonward due to the vigorous edge-driven mantle flow that erodes the craton edge, unless the craton has a distinct high viscosity mantle lithosphere. The mantle lithosphere viscosity structure determines the impact of edge-driven flow on crustal deformation and surface heat flow; a dry olivine rheology for the craton prevents the edge from migrating and supports a persistent surface heat flow contrast. These phenomena are well illustrated at the transition from the hot Canadian Cordillera to craton that is supported by a rheological change and that coincides with a lateral change in surface heat flow. Fast seismic wave velocities observed in the upper mantle cratonward of the step can be explained as downwellings induced by the edge-driven flow.

  13. Neoproterozoic stratigraphic framework of the Tarim Craton in NW China: Implications for rift evolution

    Science.gov (United States)

    Wu, Lin; Guan, Shuwei; Zhang, Shuichang; Yang, Haijun; Jin, Jiuqiang; Zhang, Xiaodan; Zhang, Chunyu

    2018-06-01

    The Tarim Craton is overlain by thick Neoproterozoic sedimentary successions in rift tectonic setting. This study examines the latest outcrop, seismic, and drilling core data with the objective of investigating the regional stratigraphy to deeply recognize the evolution of rifting in the craton. Cryogenian to Lower Ediacaran successions are mainly composed of clastic rocks with thicknesses of 2000-3000 m, and the Upper Ediacaran successions are composed of carbonate rocks with thicknesses of 500-800 m. The rift basins and stratigraphic zones are divided into northern and southern parts by a central paleo-uplift. The northern rift basin extends through the northern Tarim Craton in an E-W direction with two depocenters (Aksu and Kuruktag). The southern rift basin is oriented NE-SW. There are three or four phases of tillites in the northern zone, while there are two in the southern zone. Given the north-south difference of the stratigraphic framework, the northern rift basin initiated at ca. 740 Ma and the southern rift basin initiated at ca. 780 Ma. During the Cryogenian and Ediacaran, the northern and southern rift basins were separated by the central paleo-uplift, finally connecting with each other in the early Cambrian. Tectonic deformation in the Late Ediacaran led to the formation of a parallel unconformity in the rift basins and an angular unconformity in the central paleo-uplift. The Neoproterozoic rift basins continued to affect the distribution of Lower Cambrian hydrocarbon source rocks. The north-south distribution and evolution of the rift basins in the Tarim Craton have implications for reconstructions of the Rodinia supercontinent.

  14. Is Nubia plate rigid? A geodetic study of the relative motion of different cratonic areas within Africa.

    Science.gov (United States)

    Njoroge, M. W.; Malservisi, R.; Hugentobler, U.; Mokhtari, M.; Voytenko, D.

    2014-12-01

    Plate rigidity is one of the main paradigms of plate tectonics and a fundamental assumption in the definition of a global reference frame as ITRF. Although still far for optimal, the increased GPS instrumentation of the African region can allow us to understand how rigid one of the major plate can be. The presence of diffused band of seismicity, the Cameroon volcanic line, Pan African Kalahari orogenic belt and East Africa Rift suggest the possibility of relative motion among the different regions within the Nubia. The study focuses on the rigidity of Nubia plate. We divide the plate into three regions: Western (West Africa craton plus Nigeria), Central (approximately the region of the Congo craton) and Southern (Kalahari craton plus South Africa) and we utilize Euler Vector formulation to study internal rigidity and eventual relative motion. Developing five different reference frames with different combinations of the 3 regions, we try to understand the presence of the relative motion between the 3 cratons thus the stability of the Nubia plate as a whole. All available GPS stations from the regions are used separately or combined in creation of the reference frames. We utilize continuous stations with at least 2.5 years of data between 1994 and 2014. Given the small relative velocity, it is important to eliminate eventual biases in the analysis and to have a good estimation in the uncertainties of the observed velocities. For this reason we perform our analysis using both Bernese and Gipsy-oasis codes to generate time series for each station. Velocities and relative uncertainties are analyzed using the Allan variance of rate technique, taking in account for colored noise. An analysis of the color of the noise as function of latitude and climatic region is also performed to each time series. Preliminary results indicate a slight counter clockwise motion of West Africa craton with respect to South Africa Kalahari, and South Africa Kalahari-Congo Cratons. In addition

  15. Depth and sharpness variations of 410-km and 660-km discontinuities in North China Craton from dense array ambient noise interferometry

    Science.gov (United States)

    Yao, H.; Feng, J.; Poli, P.; Fang, L.; Wu, Y.

    2017-12-01

    Recent studies have demonstrated that body waves between pairs of stations can be successfully retrieved from ambient noise cross-correlation at both regional and global scales, although surface waves are the dominant signals. However, it is still difficult to use these retrieved body wave signals to map lateral depth variations of main structural discontinuities or velocity contrasts because of its low signal to noise ratio (SNR). In this research, based on a dense seismic array in eastern North China Craton, reflected P-wave signals from 410-km and 660-km discontinuities can be successfully recovered from ambient noise cross-correlation. To improve SNR of the reflected phases, the cross-correlations are stacked within each bin with the phase-weighted stack (PWS) method. In addition, there exist apparent spatial variations of the relative amplitude ratios between the reflected P410P and P660P phases. The retrieved P410P and P660P phases from stacked correlations reveal lateral variations of both depths and sharpness of the 410-km and 660-km discontinuities along two profiles, which may be related with hot material upwelling and the effect of stagnant Pacific plate in the transition zone beneath North China Craton. The imaging results are generally consistent with the results from teleseismic receiver functions, which demonstrate the possibility of mapping high-resolution topography and sharpness of deep internal discontinuities without earthquake-station geometric limitations. Future joint imaging with both interferometric and passive signals will be better for understanding interface architectures and related dynamic processes of the Earth.

  16. Between carbonatite and lamproite—Diamondiferous Torngat ultramafic lamprophyres formed by carbonate-fluxed melting of cratonic MARID-type metasomes

    Science.gov (United States)

    Tappe, Sebastian; Foley, Stephen F.; Kjarsgaard, Bruce A.; Romer, Rolf L.; Heaman, Larry M.; Stracke, Andreas; Jenner, George A.

    2008-07-01

    New U-Pb perovskite ages reveal that diamondiferous ultramafic lamprophyre magmas erupted through the Archean crust of northern Labrador and Quebec (eastern Canada) between ca. 610 and 565 Ma, a period of strong rifting activity throughout contiguous Laurentia and Baltica. The observed Torngat carbonate-rich aillikite/carbonatite and carbonate-poor mela-aillikite dyke varieties show a large spread in Sr-Nd-Hf-Pb isotope ratios with pronounced correlations between isotope systems. An isotopically depleted component is identified solely within aillikites ( 87Sr/ 86Sr i = 0.70323-0.70377; ɛNd i = +1.2-+1.8; ɛHf i = +1.4-+3.5; 206Pb/ 204Pb i = 18.2-18.5), whereas some aillikites and all mela-aillikites range to more enriched isotope signatures ( 87Sr/ 86Sr i = 0.70388-0.70523; ɛNd i = -0.5 to -3.9; ɛHf i = -0.6 to -6.0; 206Pb/ 204Pb i = 17.8-18.2). These contrasting isotopic characteristics of aillikites/carbonatites and mela-aillikites, along with subtle differences in their modal carbonate, SiO 2, Al 2O 3, Na 2O, Cs-Rb, and Zr-Hf contents, are consistent with two distinctive metasomatic assemblages of different age in the mantle magma source region. Integration of petrologic, geochemical, and isotopic information leads us to propose that the isotopically enriched component originated from a reduced phlogopite-richterite-Ti-oxide dominated source assemblage that is reminiscent of MARID suite xenoliths. In contrast, the isotopically depleted component was derived from a more oxidized phlogopite-carbonate dominated source assemblage. We argue that low-degree CO 2-rich potassic silicate melts from the convective upper mantle were preferentially channelled into an older, pre-existing MARID-type vein network at the base of the North Atlantic craton lithosphere, where they froze to form new phlogopite-carbonate dominated veins. Continued stretching and thinning of the cratonic lithosphere during the Late Neoproterozoic remobilized the carbonate-rich vein material and

  17. An isotopic perspective on growth and differentiation of Proterozoic orogenic crust: From subduction magmatism to cratonization

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Simon P.; Korhonen, Fawna J.; Kirkland, Christopher L.; Cliff, John B.; Belousova, Elena A.; Sheppard, Stephen

    2017-01-01

    The in situ chemical differentiation of continental crust ultimately leads to the long-term stability of the continents. This process, more commonly known as ‘cratonization’, is driven by deep crustal melting with the transfer of those melts to shallower regions resulting in a strongly chemically stratified crust, with a refractory, dehydrated lower portion overlain by a complementary enriched upper portion. Since the lower to mid portions of continental crust are rarely exposed, investigation of the cratonization process must be through indirect methods. In this study we use in situ Hf and O isotope compositions of both magmatic and inherited zircons from several felsic magmatic suites in the Capricorn Orogen of Western Australia to highlight the differentiation history (i.e. cratonization) of this portion of late Archean to Proterozoic orogenic crust. The Capricorn Orogen shows a distinct tectonomagmatic history that evolves from an active continental margin through to intracratonic reworking, ultimately leading to thermally stable crust that responds similarly to the bounding Archean Pilbara and Yilgarn Cratons.

  18. Evolution of fabric in Chitradurga granite (south India) - A study based on microstructure, anisotropy of magnetic susceptibility (AMS) and vorticity analysis

    Science.gov (United States)

    Mondal, Tridib Kumar

    2018-01-01

    In this paper, the fabric in massive granite ( 2.6 Ga) from the Chitradurga region (Western Dharwar Craton, south India) is analyzed using microstructure, anisotropy of magnetic susceptibility (AMS) study and kinematic vorticity analysis. The microstructural investigation on the granite shows a progressive textural overprint from magmatic, through high-T to low-T solid-state deformation textures. The mean magnetic foliation in the rocks of the region is dominantly NW-SE striking which have developed during regional D1/D2 deformation on account of NE-SW shortening. The plunge of the magnetic lineation varies from NW to vertical to SE, and interpreted to be a consequence of regional D3 deformation on account of NW-SE to E-W shortening. The vorticity analysis from magnetic fabric in the region reveals that the NW-SE oriented fabric formed under pure shear condition during D1/D2 regional deformation. However, some parts of the region particularly close to the adjacent Chitradurga Shear Zone show that the magnetic fabrics are oblique to the foliation as well as shear zone orientation and inferred to be controlled by simple shearing during D3 regional deformation. The shape preferred orientation (SPO) analysis from oriented thin sections suggest that the shape of the recrystallized quartz grains define the magnetic fabric in Chitradurga granite and the degree of the SPO reduces away from the Chitradurga Shear Zone. It is interpreted that the change in magnetic fabrics in some parts of the granite in the region are dominantly controlled by the late stage sinistral shearing which occurred during the development of Chitradurga Shear Zone. Anisotropy of magnetic susceptibility (AMS) data of granite from the Chitradurga region (West Dharwar Craton, southern India). Km = Mean susceptibility; Pj = corrected degree of magnetic anisotropy; T = shape parameter. K1 and K3 are the maximum and minimum principal axes of the AMS ellipsoid, respectively. dec = Declination; inc

  19. Sources and mobility of carbonate melts beneath cratons, with implications for deep carbon cycling, metasomatism and rift initiation

    Science.gov (United States)

    Tappe, Sebastian; Romer, Rolf L.; Stracke, Andreas; Steenfelt, Agnete; Smart, Katie A.; Muehlenbachs, Karlis; Torsvik, Trond H.

    2017-05-01

    Kimberlite and carbonatite magmas that intrude cratonic lithosphere are among the deepest probes of the terrestrial carbon cycle. Their co-existence on thick continental shields is commonly attributed to continuous partial melting sequences of carbonated peridotite at >150 km depths, possibly as deep as the mantle transition zone. At Tikiusaaq on the North Atlantic craton in West Greenland, approximately 160 Ma old ultrafresh kimberlite dykes and carbonatite sheets provide a rare opportunity to study the origin and evolution of carbonate-rich melts beneath cratons. Although their Sr-Nd-Hf-Pb-Li isotopic compositions suggest a common convecting upper mantle source that includes depleted and recycled oceanic crust components (e.g., negative ΔεHf coupled with > + 5 ‰ δ7Li), incompatible trace element modelling identifies only the kimberlites as near-primary low-degree partial melts (0.05-3%) of carbonated peridotite. In contrast, the trace element systematics of the carbonatites are difficult to reproduce by partial melting of carbonated peridotite, and the heavy carbon isotopic signatures (-3.6 to - 2.4 ‰ δ13C for carbonatites versus -5.7 to - 3.6 ‰ δ13C for kimberlites) require open-system fractionation at magmatic temperatures. Given that the oxidation state of Earth's mantle at >150 km depth is too reduced to enable larger volumes of 'pure' carbonate melt to migrate, it is reasonable to speculate that percolating near-solidus melts of carbonated peridotite must be silicate-dominated with only dilute carbonate contents, similar to the Tikiusaaq kimberlite compositions (e.g., 16-33 wt.% SiO2). This concept is supported by our findings from the North Atlantic craton where kimberlite and other deeply derived carbonated silicate melts, such as aillikites, exsolve their carbonate components within the shallow lithosphere en route to the Earth's surface, thereby producing carbonatite magmas. The relative abundances of trace elements of such highly

  20. Occurrence of Two Different Types of Paleoarchean TTGs in Singhbhum craton, Eastern India: Insight from Geochemistry and Zircon Saturation Thermometry

    Science.gov (United States)

    Mitra, A.; Dey, S.

    2017-12-01

    Paleoarchean era is marked as an active period of continental crust genesis. A large part of the paleoarchean crust is made up of grey sodic granitoids collectively referred as Tonalite Trondjhemite Granodiorite (TTG). Generation and evolution of TTGs are still highly debated, though researchers agree on their generation through partial melting of hydrated basalt at garnet or amphibole stability field. Discrete remnants of paleoarchean TTGs are exposed in several parts of the Singhbhum craton, eastern India. Our study exhibits occurrence of two different types of TTGs based on REE pattern in a chondrite normalized REE diagram. Accordingly, TTGs have been grouped into two different types, namely (1) High HREE TTG [low SiO2; high HREE avg. (Gd/Er)n=2.23; less fractionated REE avg. (La/Yb)n=27.9 and relatively low Sr/Y avg. Sr/Y=53.59] and Low HREE TTG [high SiO2; depleted HREE avg. (Gd/Er)n=3.23; steeply fractionated REE avg. (La/Yb)n=46.11 and relatively high Sr/Y avg. Sr/Y= 95.49]. The two types of TTGs mainly differ in pressure sensitive signatures like Sr/Y and (La/Yb)n ratio. Considering the major element composition both the types are consistent with a low-K mafic source. This indicates, melting occurred at different crustal levels from a same/similar source. Moderate Al2O3, high Sr contents coupled with depleted HREE and Y are linked to the presence of garnet in either residual or fractionating phase. However, HREE variation is controlled by the amount of Garnet retained in the restite. Thus, in spite of melting of the source rock in garnet stability field, only the minor change in depth of melting and in turn different amount of retention of garnet in the source caused the difference in HREE pattern. Zircon saturation temperature (TZr) calculated on the basis of whole rock Zr concentration ranges from 735˚C to 760 ˚C (avg. 749˚C) for high HREE TTG and 750 ˚C to 802˚C (avg. 773˚C) for low HREE TTG. Absence of zircon xenocryst depicts zircon

  1. Long wavelength magnetic anomalies over continental rifts in cratonic region

    Science.gov (United States)

    Friedman, S. A.; Persaud, P.; Ferre, E. C.; Martín-Hernández, F.; Feinberg, J. M.

    2017-12-01

    New collections of unaltered mantle xenoliths shed light on potential upper mantle contributions to long wavelength magnetic anomalies (LWMA) in continental rifts in cratonic / shield areas. The new material originates from the East African Rift (Tanzania), the Rio Grande Rift (U.S.A.), the Rhine Rift (Germany), and the West Antarctic Rift (Antarctica). The xenoliths sample the uppermost ( 0.2 or Fe geotherms (>60ºC/km) that are characteristic of rifted regions preclude any contribution to LWMA at depths >10 km. Hence, only upper basalts and hypovolcanic mafic sills would constitute potential magnetic sources. In contrast, the margins of these rifted regions consist of refractory cratonic domains, often characterized by oxidized sublithospheric mantle that host significant concentrations of primary magnetite. The higher NRMs of these peridotites (up to 15 A/m, Qn > 2.5) combined with much lower geotherms (as low as 15ºC/km) allows for a 5 to 10 km layer of uppermost mantle to potentially contribute to LWMA. Assuming that Qn values in rift margins are also gradient across the rift would primarily reflect thermal equilibration over time.

  2. Proterozoic intracontinental basin succession in the western margin of the São Francisco Craton: Constraints from detrital zircon geochronology

    Science.gov (United States)

    Martins-Ferreira, Marco Antonio Caçador; Chemale, Farid, Jr.; Dias, Airton Natanael Coelho; Campos, José Eloi Guimarães

    2018-01-01

    The age and stratigraphic position of Paleoproterozoic to Mesoproterozoic covers that occur along the western border of the São Francisco Craton (SFC) are still uncertain. Based on detailed sedimentological and stratigraphic survey, combined with U-Pb and Lu-Hf zircon dating, we present a new proposal for the stratigraphy and correlation with similar sequences, situated in other regions of the SFC, the Chapada Diamantina and Northern Espinhaço. Our study demonstrates that the so-called Traíras Formation (Araí Group) has a maximum depositional age of 1543 ± 31 Ma. The zircon distribution pattern shows a dominant Rhyacian source and minor contribution of Statherian, Calymmian, Neoarchean and Paleoarchean sources. The Rhyacian zircon grains have dominant positive εHf (t) signature, suggesting a large contribution from the juvenile Paleoproterozoic terranes, most probably from the Goiás Massif, located west of the study area. The Calymmian maximum depositional age, calculated for the upper Araí Group (Traíras Formation), leads to the conclusion that the Serra da Mesa Group (ca. 1.55 Ga maximum depositional age) and the Traíras Formation have coexisted in time, possibly forming a larger sag basin, although laterally heterogeneous. The data presented also allow a new geotectonic interpretation for the Goiás Massif, since it necessarily had to be connected to the São Francisco Craton during the Mesoproterozoic. This excludes the possibility that this massif was accreted to the São Francisco Craton in the Brasiliano Collage, as previously believed. The study also sheds light to the always debated tectonic relationship between the Serra da Mesa Granite (intrusive or basement) and Serra da Mesa Group (ca. 1.57 crystallization age and 1.55 Ga maximum depositional age, respectively). Furthermore, based on the new data, we present a stratigraphic revision for the actual Araí and Paranoá groups, proposing to raise the Traíras Formation to group status and its

  3. Shear-Velocity Structure and Azimuthal and Radial Anisotropy Beneath the Kaapvaal Craton From Bayesian Inversion of Surface-Wave Data: Inferences for the Architecture and Early Evolution of Cratons

    Science.gov (United States)

    Lebedev, S.; Ravenna, M.; Adam, J.

    2017-12-01

    Seismic anisotropy provides essential information on the deformation of the lithosphere. Knowledge of anisotropy also allows us to isolate the isotropic-average seismic velocities, relatable to the lithospheric temperature and composition. We use Rayleigh and Love-wave phase velocities and their azimuthal anisotropy measured in broad period ranges across the footprint of the Southern Africa Seismic Experiment (SASE), from the Kaapvaal Craton to the Limpopo Belt. We invert the data using our recently developed, fully non-linear Markov Chain Monte Carlo method and determine, for the first time, both the isotropic-average S velocity and its radial and azimuthal anisotropy as a function of depth from the upper crust down to the asthenosphere. The probabilistic inversion provides a way to quantify non-uniqueness, using direct parameter-space sampling, and assess model uncertainties. The high-velocity anomaly indicative of the cold cratonic lithosphere bottoms at 200-250 km beneath the central and western Kaapvaal Craton, underlain by a low-velocity zone. Beneath northern Kaapvaal and Limpopo, by contrast, high velocities extend down to 300-350 km. Although this does not require a lithosphere that has maintained this thickness over a geologically long time, the data does require the mantle to be anomalously cold down to 300-350 km. Interestingly, topography correlates with the thickness of this high-velocity layer, with lower elevations where the lid is thicker. Radial shear-wave anisotropy is in the 2-5 percent range (Vsh > Vsv) from the lower crust down to 200 km, below which depth it decreases gradually. Radial variations in the amplitude of radial anisotropy show no clear relationship with those in the amplitude of azimuthal anisotropy or isotropic-average Vs anomalies. Azimuthal anisotropy changes the fast-propagation direction near the base of the lithosphere (200-300 km depth), from the laterally varying fast azimuths in the lower lithosphere to a spatially

  4. Accretionary Tectonics of Rock Complexes in the Western Margin of the Siberian Craton

    Science.gov (United States)

    Likhanov, I. I.; Nozhkin, A. D.; Savko, K. A.

    2018-01-01

    The geological, geochemical, and isotope-geochronological evidence of the events at the final stage of the Neoproterozoic history of the Yenisei Range is considered (beginning from the formation of fragments of the oceanic crust in the region and their accretion to the Siberian Craton until the postaccretionary stage of crustal tension and onset of the Caledonian orogeny). Based on an analysis of new data on the petrogeochemical composition, age, and geodynamic nature of the formation of contrasting rocks in the composition of tectonic mélange of the Near-Yenisei (Prieniseiskaya) regional shear zone, we have found the chronological sequence of events that marks the early stages of the Paleoasian Ocean evolution in the zone of its junction with the Siberian Craton. These events are documented by the continental marginal, ophiolitic, and island-arc geological complexes, each of which has different geochemical features. The most ancient structures are represented by fragments of oceanic crust and island arcs from the Isakovka terrane (700-620 Ma). The age of glaucophane-schist metamorphic units that formed in the paleosubduction zone corresponds to the time interval of 640-620 Ma. The formation of high-pressure tectonites in the suture zone, about 600 Ma in age, marks the finishing stage of accretion of the Isakovka block to the western margin of the Siberian Craton. The final events in the early history of the Asian Paleoocean were related to the formation of Late Vendian riftogenic amygdaloidal basalts (572 ± 6.5 Ma) and intrusion of postcollisional leucogranites of the Osinovka massif (550-540 Ma), which intruded earlier fragments of the oceanic crust in the Isakovka terrane. These data allow us to refine the Late Precambrian stratigraphic scheme in the northwestern Trans-Angarian part of the Yenisei Range and the evolutionary features of the Sayan-Yenisei accretionary belt. The revealed Late Neoproterozoic landmarks of the evolution of the Isakovka terrane are

  5. An isotopic perspective on growth and differentiation of Proterozoic orogenic crust: From subduction magmatism to cratonization

    Science.gov (United States)

    Johnson, Simon P.; Korhonen, Fawna J.; Kirkland, Christopher L.; Cliff, John B.; Belousova, Elena A.; Sheppard, Stephen

    2017-01-01

    The in situ chemical differentiation of continental crust ultimately leads to the long-term stability of the continents. This process, more commonly known as 'cratonization', is driven by deep crustal melting with the transfer of those melts to shallower regions resulting in a strongly chemically stratified crust, with a refractory, dehydrated lower portion overlain by a complementary enriched upper portion. Since the lower to mid portions of continental crust are rarely exposed, investigation of the cratonization process must be through indirect methods. In this study we use in situ Hf and O isotope compositions of both magmatic and inherited zircons from several felsic magmatic suites in the Capricorn Orogen of Western Australia to highlight the differentiation history (i.e. cratonization) of this portion of late Archean to Proterozoic orogenic crust. The Capricorn Orogen shows a distinct tectonomagmatic history that evolves from an active continental margin through to intracratonic reworking, ultimately leading to thermally stable crust that responds similarly to the bounding Archean Pilbara and Yilgarn Cratons. The majority of magmatic zircons from the main magmatic cycles have Hf isotopic compositions that are generally more evolved than CHUR, forming vertical arrays that extend to moderately radiogenic compositions. Complimentary O isotope data, also show a significant variation in composition. However, combined, these data define not only the source components from which the magmas were derived, but also a range of physio-chemical processes that operated during magma transport and emplacement. These data also identify a previously unknown crustal reservoir in the Capricorn Orogen.

  6. Cratonic roots and lower crustal seismicity: Investigating the role of deep intrusion in the Western rift, Africa

    Science.gov (United States)

    Drooff, C.; Ebinger, C. J.; Lavayssiere, A.; Keir, D.; Oliva, S. J.; Tepp, G.; Gallacher, R. J.

    2017-12-01

    Improved seismic imaging beneath the African continent reveals lateral variations in lithospheric thickness, and crustal structure, complementing a growing crust and mantle xenolith data base. Border fault systems in the active cratonic rifts of East Africa are characterized by lower crustal seismicity, both in magmatic sectors and weakly magmatic sectors, providing constraints on crustal rheology and, in some areas, magmatic fluid migration. We report new seismicity data from magmatic and weakly magmatic sectors of the East African rift zone, and place the work in the context of independent geophysical and geochemical studies to models for strain localization during early rifting stages. Specifically, multidisciplinary studies in the Magadi Natron rift sectors reveal volumetrically large magmatic CO2 degassing along border faults with seismicity along projections of surface dips to the lower crust. The magmatic CO2 degassing and high Vp/Vs ratios and reflectivity of the lower crust implies that the border fault serves a conduit between the lower crustal underplating and the atmospheric. Crustal xenoliths in the Eastern rift sector indicate a granulitic lower crust, which is relatively weak in the presence of fluids, arguing against a strong lower crust. Within magmatic sectors, seismic, structural, and geochemistry results indicate that frequent lower crustal earthquakes are promoted by elevated pore pressures from volatile degassing along border faults, and hydraulic fracture around the margins of magma bodies. Within some weakly magmatic sectors, lower crustal earthquakes also occur along projections of border faults to the lower crust (>30 km), and they are prevalent in areas with high Vp/Vs in the lower crust. Within the southern Tanganyika rift, focal mechanisms are predominantly normal with steep nodal planes. Our comparative studies suggest that pervasive metasomatism above a mantle plume, and melt extraction in thin zones between cratonic roots, lead to

  7. Mesoproterozoic evolution of the Río de la Plata Craton in Uruguay: at the heart of Rodinia?

    Science.gov (United States)

    Gaucher, Claudio; Frei, Robert; Chemale, Farid; Frei, Dirk; Bossi, Jorge; Martínez, Gabriela; Chiglino, Leticia; Cernuschi, Federico

    2011-04-01

    Mesoproterozoic volcanosedimentary units and tectonic events occurring in the Río de la Plata Craton (RPC) are reviewed. A belt consisting of volcanosedimentary successions exhibiting greenschist-facies metamorphism is exposed in the eastern RPC (Nico Pérez Terrane) in Uruguay. The Parque UTE Group consists of basic volcanics and gabbros at the base (1,492 ± 4 Ma, U-Pb on zircon), carbonates in its middle part and interbedded carbonates, shales and acid volcanics (1,429 ± 21 Ma, U-Pb on zircon) at the top. The Mina Verdún Group is made up of rhyolites and acid pyroclastics at its base and top, and Conophyton-bearing limestones and massive dolostones in the middle. A U-Pb LA-ICP MS zircon age of 1,433 ± 6 Ma is reported here for lapilli-tuffs at the base of the Mina Verdún Group (Cerro de las Víboras Formation). This age shows that the Mina Verdún Group immediately postdates the Parque UTE Group, a fact supported by carbon isotope chemostratigraphy. Both units were deformed and metamorphosed between 1.25 and 1.20 Ga, as shown by K-Ar and Ar-Ar ages. This tectonic event affected most of the RPC and led to the accretion of the Nico Pérez Terrane to the remainder of the RPC along the Sarandí del Yí megashear. We report a U-Pb LA-ICP MS zircon age (upper intercept) of 3,096 ± 45 Ma for metatonalites of the La China Complex (Nico Pérez Terrane), which yield a lower intercept age of 1,252 Ma. A proto-Andean, Mesoproterozoic belt is envisaged to account for abundant Mesoproterozoic detrital zircon ages occurring in Ediacaran sandstones of the RPC. If the RPC is fringed at both sides by Mesoproterozoic, Grenville-aged belts it is likely that it occupied a rather central position in Rodinia. A possible location between Laurentia and the Kalahari Craton, and to the south of Amazonia, is suggested.

  8. PALEOARCHEAN MAFIC ROCKS OF THE SOUTHWESTERN SIBERIAN CRATON: PRELIMINARY GEOCHRONOLOGY AND GEOCHEMICAL CHARACTERIZATION

    Directory of Open Access Journals (Sweden)

    A. V. Ivanov

    2017-01-01

    Full Text Available The Siberian craton consists of Archean blocks, which were welded up into the same large unit by ca 1.9 Ga [Gladkochub et al., 2006; Rojas-Agramonte et al., 2011]. The history of the constituent Archean blocks is mosaic because of limited number of outcrops, insufficient sampling coverage because of their location in remote regions and deep forest and difficulties with analytical studies of ancient rocks, which commonly underwent metamorphic modifications and secondary alterations. In this short note, we report data on discovery of unusual for Archean mafic rocks of ultimate fresh appearance. These rocks were discovered within southwestern Siberian craton in a region near a boundary between Kitoy granulites of the Sharyzhalgai highgrade metamorphic complex and Onot green-schist belt (Fig. 1. Here we present preliminary data on geochronology of these rocks and provide their geochemical characterization.

  9. Lower Crustal Seismicity, Volatiles, and Evolving Strain Fields During the Initial Stages of Cratonic Rifting

    Science.gov (United States)

    Lambert, C.; Muirhead, J.; Ebinger, C. J.; Tiberi, C.; Roecker, S. W.; Ferdinand-Wambura, R.; Kianji, G.; Mulibo, G. D.

    2014-12-01

    The volcanically active East African rift system in southern Kenya and northern Tanzania transects thick cratonic lithosphere, and comprises several basins characterized by deep crustal seismicity. The US-French-Tanzania-Kenya CRAFTI project aims to understand the role of magma and volatile movement during the initiation and evolution of rifting in cratonic lithosphere. Our 38-station broadband network spans all or parts of fault-bounded rift segments, enabling comparison of lithospheric structure, fault kinematics, and seismogenic layer thickness with age and proximity to the deeply rooted Archaen craton. Seismicity levels are high in all basins, but we find profound differences in seismogenic layer thickness along the length of the rift. Seismicity in the Manyara basin occurs almost exclusively within the lower crust, and in spatial clusters that have been active since 1990. In contrast, seismicity in the ~ 5 My older Magadi basin is localized in the upper crust, and the long border fault bounding the west side of the basin is seismically inactive. Between these two basins lies the Natron rift segment, which shows seismicity between ~ 20 and ~2 km depth, and high concentrations at Oldoinyo Lengai and Gelai volcanoes. Older volcanoes on the uplifted western flank (e.g., Ngorongoro) experience swarms of activity, suggesting that active magmatism and degassing are widespread. Focal mechanisms of the frequent earthquakes recorded across the array are spatially variable, and indicate a stress field strongly influenced by (1) Holocene volcanoes, (2) mechanical interactions between adjacent rift basins, and (3) a far-field ESE-WNW extensional stress regime. We explore the spatial correlation between zones of intense degassing along fault systems and seismicity, and examine the influence of high gas pressures on lower and upper crustal seismicity in this youthful cratonic rift zone.

  10. Exploring Moho sharpness in Northeastern North China Craton with frequency-dependence analysis of Ps receiver function

    Science.gov (United States)

    Zhang, P.; Yao, H.; Chen, L.; WANG, X.; Fang, L.

    2017-12-01

    The North China Craton (NCC), one of the oldest cratons in the world, has attracted wide attention in Earth Science for decades because of the unusual Mesozoic destruction of its cratonic lithosphere. Understanding the deep processes and mechanism of this craton destruction demands detailed knowledge about the deep structure of this region. In this study, we calculate P-wave receiver functions (RFs) with two-year teleseismic records from the North China Seismic Array ( 200 stations) deployed in the northeastern NCC. We observe both diffused and concentered PpPs signals from the Moho in RF waveforms, which indicates heterogeneous Moho sharpness variations in the study region. Synthetic Ps phases generated from broad positive velocity gradients at the depth of the Moho (referred as Pms) show a clear frequency dependence nature, which in turn is required to constrain the sharpness of the velocity gradient. Practically, characterizing such a frequency dependence feature in real data is challenging, because of low signal-to-noise ratio, contaminations by multiples generated from shallow structure, distorted signal stacking especially in double-peak Pms signals, etc. We attempt to address these issues by, firstly, utilizing a high-resolution Moho depth model of this region to predict theoretical delay times of Pms that facilitate more accurate Pms identifications. The Moho depth model is derived by wave-equation based poststack depth migration on both Ps phase and surface-reflected multiples in RFs in our previous study (Zhang et al., submitted to JGR). Second, we select data from a major back azimuth range of 100° - 220° that includes 70% teleseismic events due to the uneven data coverage and to avoid azimuthal influence as well. Finally, we apply an adaptive cross-correlation stacking of Pms signals in RFs for each station within different frequency bands. High-quality Pms signals at different frequencies will be selected after careful visual inspection and adaptive

  11. Mechanisms for strain localization within Archaean craton: A structural study from the Bundelkhand Tectonic Zone, north-central India

    Science.gov (United States)

    Sarkar, Saheli; Patole, Vishal; Saha, Lopamudra; Pati, Jayanta Kumar; Nasipuri, Pritam

    2015-04-01

    The transformation of palaeo-continents involve breakup, dispersal and reassembly of cratonic blocks by collisional suturing that develop a network of orogenic (mobile) belts around the periphery of the stable cratons. The nature of deformation in the orogenic belt depends on the complex interaction of fracturing, plastic deformation and diffusive mass transfer. Additionally, the degree and amount of melting during regional deformation is critical as the presence of melt facilitates the rate of diffusive mass transfer and weakens the rock by reducing the effective viscosity of the deformed zone. The nature of strain localization and formation of ductile shear zones surrounding the cratonic blocks have been correlated with Proterozoic-Palaeozoic supercontinent assembly (Columbia, Rodinia and Gondwana reconstruction). Although, a pre-Columbia supercontinent termed as Kenorland has been postulated, there is no evidence that supports the notion due to lack of the presence of shear zones within the Archaean cratonic blocks. In this contribution, we present the detailed structural analysis of ductile shear zones within the Bundelkhand craton. The ductlile shear zone is termed as Bundelkhand Tectonic Zone (BTZ) that extends east-west for nearly 300 km throughout the craton with a width of two-three kilometer . In the north-central India, the Bundelkhand craton is exposed over an area of 26,000 sq. The craton is bounded by Central Indian Tectonic zone in the south, the Great Boundary fault in the west and by the rocks of Lesser Himalaya in the north. A series of tonalite-trondjhemite-granodiorite gneiss are the oldest rocks of the Bundelkhand craton that also contains a succession of metamorphosed supracrustal rocks comprising of banded iron formation, quartzite, calc-silicate and ultramafic rocks. K-feldspar bearing granites intrude the tonalite-trondjhemite-granodiorite and the supracrustal rocks during the time span of 2.1 to 2.5 Ga. The TTGs near Babina, in central

  12. Geochemical fingerprinting of ∼2.5 Ga forearc-arc-backarc related magmatic suites in the Bastar Craton, central India

    Science.gov (United States)

    Asthana, Deepanker; Kumar, Sirish; Vind, Aditya Kumar; Zehra, Fatima; Kumar, Harshavardhan; Pophare, Anil M.

    2018-05-01

    The Pitepani volcanic suite of the Dongargarh Supergroup, central India comprises of a calc-alkaline suite and a tholeiitic suite, respectively. The rare earth element (REE) patterns, mantle normalized plots and relict clinopyroxene chemistry of the Pitepani calc-alkaline suite are akin to high-Mg andesites (HMA) and reveal remarkable similarity to the Cenozoic Setouchi HMA from Japan. The Pitepani HMAs are geochemically correlated with similar rocks in the Kotri-Dongargarh mobile belt (KDMB) and in the mafic dykes of the Bastar Craton. The rationale behind lithogeochemical correlations are that sanukitic HMAs represent fore-arc volcanism over a very limited period of time, under abnormally high temperature conditions and are excellent regional and tectonic time markers. Furthermore, the tholeiitic suites that are temporally and spatially associated with the HMAs in the KDMB and in the mafic dykes of the Bastar Craton are classified into: (a) a continental back-arc suite that are depleted in incompatible elements, and (b) a continental arc suite that are more depleted in incompatible elements, respectively. The HMA suite, the continental back-arc and continental arc suites are lithogeochemically correlated in the KDMB and in the mafic dykes of the Bastar Craton. The three geochemically distinct Neoarchaean magmatic suites are temporally and spatially related to each other and to an active continental margin. The identification of three active continental margin magmatic suites for the first time, provides a robust conceptual framework to unravel the Neoarchaean geodynamic evolution of the Bastar Craton. We propose an active continental margin along the Neoarchaen KDMB with eastward subduction coupled with slab roll back or preferably, ridge-subduction along the Central Indian Tectonic Zone (CITZ) to account for the three distinct magmatic suites and the Neoarchean geodynamic evolution of the Bastar Craton.

  13. The kinematic evolution of the Serra Central Salient, Eastern Brazil: A Neoproterozoic progressive arc in northern Espinhaço fold-thrust belt

    Science.gov (United States)

    Bersan, Samuel Moreira; Danderfer, André; Lagoeiro, Leonardo; Costa, Alice Fernanda de Oliveira

    2017-12-01

    Convex-to-the-foreland map-view curves are common features in fold-thrust belts around cratonic areas. These features are easily identifiable in belts composed of supracrustal rocks but have been rarely described in rocks from relatively deeper crustal levels where plastic deformation mechanisms stand out. Several local salients have been described in Neoproterozoic marginal fold-thrust belts around the São Francisco craton. In the northern part of the Espinhaço fold-thrust belt, which borders the eastern portion of the São Francisco craton, both Archean-Paleoproterozoic basement rocks and Proterozoic cover rocks are involved in the so-called Serra Central salient. A combination of conventional structural analysis and microstructural and paleostress studies were conducted to characterize the kinematic and the overall architecture and processes involved in the generation of this salient. The results allowed us to determine that the deformation along the Serra Central salient occur under low-grade metamorphic conditions and was related to a gently oblique convergence with westward mass transport that developed in a confined flow, controlled by two transverse bounding shear zones. We propose that the Serra Central salient nucleates as a basin-controlled primary arc that evolves to a progressive arc with secondary vertical axis rotation. This secondary rotation, well-illustrated by the presence of two almost orthogonal families of folds, was dominantly controlled by buttress effect exert by a basement high located in the foreland of the Serra Central salient.

  14. Compositional variations in the Mesoarchean chromites of the Nuggihalli schist belt, Western Dharwar Craton (India)

    DEFF Research Database (Denmark)

    Mukherjee, Ria; Mondal, Sisir Kanti; Rosing, Minik Thorleif

    2010-01-01

    in silicate-rich chromitite (similar to 50% modal chromite) and serpentinite (similar to 2% modal chromite) throughout the entire ultramafic sequence. However, the primary composition of chromite is preserved in the massive chromitites (similar to 60-75% modal chromite) from the Byrapur and the Bhaktarhalli...

  15. The Amazon-Laurentian connection as viewed from the Middle Proterozoic rocks in the central Andes, western Bolivia and northern Chile

    Science.gov (United States)

    Tosdal, R.M.

    1996-01-01

    between these cratons and seemingly precluding part of the Arequipa-Antofalla craton from being a detached fragment of another craton such as eastern Laurentia, which has been characterized by a different U/Pb history. Pb isotopic compositions for the Arequipa-Antofalla craton are, furthermore, distinct from those of the Proterozoic basement in the Precordillera terrane, western Argentina, indicating a Pb isotopic and presumably a tectonic boundary between them. The Pb isotopic compositions for the Precordillera basement are similar to those of eastern Laurentia, and support other data indicating that these rocks are a detached fragment of North America. Finally, the distinct Pb isotopic evolution history of the Arequipa-Antofalla craton and eastern Laurentia require minor modification to tectonic models linking eastern North America-Scotland to the oroclinal bend in western South America.

  16. Evolution of Hutti-Maski greenstone belt of the Eastern Dharwar ...

    Indian Academy of Sciences (India)

    53

    the Hutti-Maski greenstone belt have been studied by several workers (Iyer and Vasudev. 32. 1979 ..... In the present case it is clear that there is overgrowth of garnet on a. 246 core grain. ...... Mg) phase relations; Am. Jour. Science, 276 ...

  17. Gravity and magnetic modelling in the Vrancea Zone, south-eastern Carpathians: Redefinition of the edge of the East European Craton beneath the south-eastern Carpathians

    NARCIS (Netherlands)

    Bocin, A.; Stephenson, R.; Matenco, L.; Mocanu, V.

    2013-01-01

    A 2D gravity and magnetic data model has been constructed along a 71. km densely observed profile, called DACIA PLAN GRAV MAN's. The profile crosses part of the nappe pile of the south-eastern Carpathians and includes the seismically active Vrancea Zone and was acquired with the objective to

  18. The Amazonian Craton and its influence on past fluvial systems (Mesozoic-Cenozoic, Amazonia)

    NARCIS (Netherlands)

    Hoorn, C.; Roddaz, M.; Dino, R.; Soares, E.; Uba, C.; Ochoa-Lozano, D.; Mapes, R.; Hoorn, C.; Wesselingh, F.P.

    2010-01-01

    The Amazonian Craton is an old geological feature of Archaean/Proterozoic age that has determined the character of fluvial systems in Amazonia throughout most of its past. This situation radically changed during the Cenozoic, when uplift of the Andes reshaped the relief and drainage patterns of

  19. Gravity Data Interpretation in the Northern Edge of the Congo Craton, South-Cameroon

    Directory of Open Access Journals (Sweden)

    James Derek Fairhead

    2010-01-01

    Full Text Available Gravity data in the southern Cameroon are interpreted to better understand the organization of underlying structuresthroughout the northern edge of the Congo craton. The Bouguer anomaly maps of the region are characterized by an elongated trending trending negative gravity anomaly which correspond to a collapsed structure associated with a granitic intrusion beneath the cente center of the region r of the region of the region and limited by fault systems. �e applied 3�D gravity modelling and inversion in order to obtain the 3D density structure of the area. Our result demonstrated that observed gravity anomalies in the region are associated to tectonic structures in the subsurface. The resulting model agrees with the hypothesis of the existence of a major continental collision zone between the Congo Craton and the Pan�African belt. The presence of deep granulites structures in the northern part of the region expresses a continental collision.

  20. 1.60 Ga felsic volcanic blocks in the moraines of the Terre Adelie Craton, Antarctica: comparisons with the Gawler Range Volcanics, South Australia

    International Nuclear Information System (INIS)

    Peucat, J.J.; Capdevila, R.; Pecora, L.; Fanning, C.M.; Testut, L.

    2002-01-01

    Rhyodacite and rhyolite blocks found in numerous moraines on the Terre Adelie Craton in Antarctica are samples of a high-temperature high-K calc-alkaline to alkali-calcic igneous suite emplaced at ca 1.60Ga. They comprise lavas and pyroclastic rocks, including ignimbritic varieties, chemically representative of anorogenic and post-orogenic igneous suites. The eruptive centres are probably close to the coast according to radar satellite images that show the trace of the ice streams. The volcanic suite is similar in age, petrography and chemical composition (major and trace elements as well as Nd isotopes) to the Gawler Range Volcanics from the Gawler Craton of South Australia. These similarities strengthen correlations previously established between the Gawler Craton and the Terre Adelie Craton (Mawson Continent). Moreover, the present petrological, geochemical and geochronological data give a new insight into the last major thermal event affecting the Mawson Continent. The results also highlight the useful contribution of moraines to our knowledge of Antarctic geology. Copyright (2002) Geological Society of Australia

  1. An Integrated Geochronological, Petrological, Geochemical and Paleomagnetic Study of Paleoproterozoic and Mesoproterozoic Mafic Dyke Swarms in the Nain Craton, Labrador

    Science.gov (United States)

    Sahin, Tugce

    The Nain craton comprises the western, Labrador segment of the larger North Atlantic craton (NAC) which exposes Early through Late Archean gneisses. The NAC is bounded on all sides by Paleoproterozoic collisional orogens that involved either considerable structural reworking (Torngat-Nagssugtoqidian-Lewisian) or the accretion of juvenile arc magmas (Ketilidian-Makkovik). The NAC remains poorly understood compared to other Archean crustal blocks now dispersed globally. Compounding this problem is a lack of reliable paleomagnetic poles for NAC units that predate its assembly into the supercontinent Laurentia by ca. 1800 Ma, which could be used to test neighboring relationships with other cratonic fragments. In order to understand the history of the NAC as part of a possible, larger supercontinent, the record of mafic dyke swarms affecting the craton, particularly those that postdate the Late Archean terrane assembly, were examined in this study. Diabase or gabbroic dyke swarms are invaluable in such studies because their geometries offer possible locus points, they often have a punctuated emplacement and precisely datable crystallization histories, and they have cooling histories and oxide mineralogy amenable to recovering robust paleopoles. Coastal Labrador exposes a number of mafic dykes, some of which are demonstrably Paleoproterozoic (e.g. 2235 Ma Kikkertavak dykes; 2121 Ma Tikkigatsiagak dykes) or Mesoproterozoic (e.g. 1280-1270 Ma Nain and Harp dykes) in age (U-Pb; baddeleyite or zircon). The southern half of the Nain craton (Hopedale block) in particular preserves a rich array of mafic dykes. Dyke cross-cutting relationships are numerous and relatively well exposed, permitting multiple opportunities for paleomagnetic field tests (e.g. baked contact). The results presented here allow understanding of the tectonic evolution of the NAC with implications for strengthened Labrador-Greenland correlations, and testing possible Paleoproterozoic supercontinent

  2. Western cratonic domains in Uruguay: geochronology

    International Nuclear Information System (INIS)

    Preciozzi, F.; Peel, E.; Muzio, E.; Ledesma, R.; Guerequiz, R.

    2001-01-01

    The western cratonic domains in Uruguay are divided into three major units: Piedra Alta Terrane, Valentines Block and Pavas Block. Piedra Alta Terrane lacks of evidence of Neoproterozoic orogenesis (deformation, metamorphism or magmatism). Sarandí del Yi - Arroyo Solís Grande shear zone, separates it from Valentines Block. Valentines Block is separated from Pavas Block by Cueva del Tigre shear zone. Magmatic rocks with different ages, compositions and emplacements occur all over the Piedra Alta Terrane distributed in three metamorphic belts (Arroyo Grande, San José and Montevideo) as well as in the Central Gneissic-Migmatitic Complex (Figure 1). Samples from the Gneissic-Migmatitic complex, late tectonic granitoids and basic rocks associated to the metamorphic belts were analyzed using Rb/Sr, U/Pb, K/Ar and Sm/Nd methodologies. The age ranges obtained for granitoids

  3. Paleomagnetic Results of the 925 Ma Mafic Dykes From the North China Craton: Implications for the Neoproterozoic Paleogeography of Rodinia

    Science.gov (United States)

    Zhao, X.; Peng, P.

    2017-12-01

    Precambrian mafic dyke swarms are useful geologic records for Neoproterozoic paleogeographic reconstruction. We present a paleomagnetic study of the 925 Ma Dashigou dyke swarm from 3 widely separated locations in the central and northern parts of the North China Craton, which are previously unsampled regions. Stepwise thermal and alternating field demagnetizations were successful in isolating two magnetic components. The lower unblocking temperature component represents the recent Earth magnetic field. The higher unblocking temperature component is the characteristic remanent magnetization and yields positive baked contact test. Results from detailed rock magnetic measurements corroborate the demagnetization behavior and show that titanomagnetites are the main magnetic carrier in these rocks. There was no regional event that has reset the remanent magnetization of all the dyke sites, as indicated by the magnetization directions of both overlying and underlying strata. The similarity of the virtual paleomagnetic poles for the 3 sampled regions also argues that the characteristic remanent magnetizations are primary magnetization when the dykes were emplaced. The paleomagnetic poles from the Dashigou dyke swarm of the North China Craton are not similar to those of the identical aged Bahia dykes from the São Francisco Craton, Brazil, indicating that these mafic dykes may be not parts of a common regional magmatic event that affected North China Craton and NE Brazil at about 925 Ma.

  4. Some problems of geologic relations between the Amazon craton and east margins fold belts

    International Nuclear Information System (INIS)

    Almeida, F.F.M. de

    1986-01-01

    This paper deals with some geologic problems related to the limits between the Amazon craton and the fold belts developed at its margins during the Precambrian. These limits are diversified but clearly recognized. To the north, the Araguaia-Tocantins fold belt, of presumed Middle Proterozoic age, is separated from the cratonic block by a deep marginal fracture zone permeated by mafic and ultramafic rocks. The geologic, magmatic and aeromagnetic characteristics of this zone point out the presence of deep faults, supposed to be of Middle Proterozoic age. The southern Paraguay fold belt constitutes and accurated zone of linear structures supposed to be of Late Proterozoic development. Despite the great increase of knowledge during the last ten years many tectonic, stratigraphic and geochronologic problems remain unsolved. The aim of this paper is to point out some of these problems and suggest specific studies to solve them. (author)

  5. APW path traced for the Guiana Shield (2070-1960 Ma) and Paleogeographic Implications: Paleomagnetic data from the 1.98-1.96 Ga Surumu Group (Northern Amazonian Craton)

    Science.gov (United States)

    Bispo-Santos, F.; Dagrella Filho, M. S.; Reis, N. J.; Trindade, R. I.

    2013-05-01

    Definition of continental paleogeography for times prior to formation of Columbia Supercontinent (1900-1850 Ma) is very complex, since amalgamation of some continental blocks of Earth was still in progress, as in the case of Laurentia, Baltica and Amazonian Craton. So, paleogeographic models proposed for this time are still very speculative and/or subjective. The use of the paleomagnetic technique tracing apparent polar wander (APW) paths for the various cratonic blocks can contribute to understand the continental amalgamation and breakup, especially for times where all created oceanic lithosphere was fully consumed. In this study, we present the paleomagnetic data obtained for samples collected from 39 sites from the well-dated 1980-1960 Ma (U-Pb) volcanic rocks belonging to the Surumu Group, cropping out in the northern Roraima State (Guiana Shield, Amazonian Craton). AF and thermal treatment revealed northwestern directions with moderate downward inclinations on samples from 20 out of the 39 analyzed sites. Site mean directions cluster around the mean, Dm = 298.6°; Im = 39.4° (N = 20; α95 = 10.1°), which yielded a key paleomagnetic pole (SG) for the Guiana Shield, located at 234.8°E, 27.4°N (A95 = 9.8°). Magnetic mineralogy experiments show that the magnetization of these rocks, probably of primary origin, is carried by magnetite and/or hematite. The SG pole contributes to a better fit of the APW path traced for Guiana Shield during the Paleoproterozoic (2070-1960 Ma). Comparison with the APW path traced for the West-Africa Craton for the same time interval suggests that these cratonic blocks were linked at 2000-1960 Ma ago, forming a paleogeography in which the Guri (Guiana Shield) and Sassandra (West-Africa Craton) shear zones were aligned as suggested in previous geologic models. KEYWORDS: Paleoproterozoic, Paleomagnetism, APWP, Amazonian Craton, Surumu Group.

  6. Contrast of lithospheric dynamics across the southern and eastern margins of the Tibetan Plateau: a numerical study

    Science.gov (United States)

    Sun, Yujun; Fan, Taoyuan; Wu, Zhonghai

    2018-05-01

    Both of the southern and eastern margins of the Tibetan Plateau are bounded by the cratonic blocks (Indian plate and Sichuan basin). However, there are many differences in tectonic deformation, lithospheric structure and surface heat flow between these two margins. What dynamics cause these differences? With the constraints of the lithospheric structure and surface heat flow across the southern and eastern margins of Tibetan Plateau, we constructed 2-D thermal-mechanical finite-element models to investigate the dynamics across these two margins. The results show that the delamination of mantle lithosphere beneath the Lhasa terrane in Oligocene and the rheological contrast between the Indian and Tibetan crust are the two main factors that control the subduction of the Indian plate. The dynamics across the eastern margin of the Tibetan Plateau are different from the southern margin. During the lateral expansion of the Tibetan Plateau, pure shear thickening is the main deformation characteristic for the Songpan-Ganzi lithosphere. This thickening results in the reduction of geothermal gradient and surface heat flow. From this study, it can be seen that the delamination of the mantle lithosphere and the rheological contrast between the Tibetan Plateau and its bounding blocks are the two main factors that control the lithospheric deformation and surface heat flow.

  7. High-resolution sequence stratigraphy of lower Paleozoic sheet sandstones in central North America: The role of special conditions of cratonic interiors in development of stratal architecture

    Science.gov (United States)

    Runkel, Anthony C.; Miller, J.F.; McKay, R.M.; Palmer, A.R.; Taylor, John F.

    2007-01-01

    Well-known difficulties in applying sequence stratigraphic concepts to deposits that accumulated across slowly subsiding cratonic interior regions have limited our ability to interpret the history of continental-scale tectonism, oceanographic dynamics of epeiric seas, and eustasy. We used a multi-disciplinary approach to construct a high-resolution stratigraphic framework for lower Paleozoic strata in the cratonic interior of North America. Within this framework, these strata proved readily amenable to modern sequence stratigraphic techniques that were formulated based on successions along passive margins and in foreland basins, settings markedly different from the cratonic interior. Parasequences, parasequence stacking patterns, systems tracts, maximum flooding intervals, and sequence-bounding unconformities can be confidently recognized in the cratonic interior using mostly standard criteria for identification. The similarity of cratonic interior and foreland basin successions in size, geometry, constituent facies, and local stacking patterns of nearshore parasequences is especially striking. This similarity indicates that the fundamental processes that establish shoreface morphology and determine the stratal expression of retreat and progradation were likewise generally the same, despite marked differences in tectonism, physiography, and bathymetry between the two settings. Our results do not support the widespread perception that Paleozoic cratonic interior successions are so anomalous in stratal geometries, and constitute such a poor record of time, that they are poorly suited for modern sequence stratigraphic analyses. The particular arrangement of stratal elements in the cratonic interior succession we studied is no more anomalous or enigmatic than the variability in architecture that sets all sedimentary successions apart from one another. Thus, Paleozoic strata of the cratonic interior are most appropriately considered as a package that belongs in a

  8. Geochemistry of organic-rich river waters in Amazonia: Insights on weathering processes of intertropical cratonic terrain

    International Nuclear Information System (INIS)

    Horbe, Adriana Maria Coimbra; Lages, Anderson da Silva; Moquet, Jean-Sébastien; Santos, Roberto Ventura; Seyler, Patrick

    2016-01-01

    In this study, eight organic-rich rivers that flow through the Brazilian craton in the southwestern Amazon rainforest are investigated. This investigation is the first of its type in this area and focuses on the effects of lithology, long-term weathering, thick soils, forest cover and hydrological period on the dissolved load compositions in rivers draining cratonic terrain. The major dissolved ion concentrations, alkalinity (TAlk), SiO 2 , trace element concentrations, and Sr isotope contents in the water were determined between April 2009 and January 2010. In addition, the isotopic values of oxygen and hydrogen were determined between 2011 and 2013. Overall, the river water is highly dilute and dominated by the major dissolved elements TAlk, SiO 2 and K + and the major dissolved trace elements Al, Fe, Ba, Mn, P, Zn and Sr, which exhibit large temporal and spatial variability and are closely correlated with the silicatic bedrock and hydrology. Additionally, rainwater and recycled water vapor and the size of the basin contribute to the geochemistry of the waters. The total weathering flux estimated from our results is 2–4 t km −2 .yr −1 , which is one of the lowest fluxes in the world. The CO 2 consumption rate is approximately 21–61 10 3  mol km −2  yr −1 , which is higher than expected given the stability of the felsic to basic igneous and metamorphic to siliciclastic basement rocks and the thick tropical soil cover. Thus, weathering of the cratonic terrain under intertropical humid conditions is still an important consumer of CO 2 . - Highlights: • Were studied rivers flowing the Brazilian craton covered by lateritic soils. • The river waters are highly diluted and dominated by TAlk, SiO 2 and K + . • There is spatial and temporal variability in the chemical composition. • The rain amount and recycled water vapor affect the O and D isotopes. • Geology, weathering, discharge and seasonality highlight a singular composition.

  9. Preliminary Evidence for a Second -525-545 Ma old Event of ...

    African Journals Online (AJOL)

    (1995), the 630-700 Ma old event that produced the Eastern Granulites may record regional crustal thickening arising out of collision of India, Madagascar, parts of Easten Antarctica and the Kalahari craton (IMSLEK terranes) with the Congo craton and the Arabian Nubian Shield (ANS). The younger granulite event recorded ...

  10. Short-Wavelength Infrared (SWIR) spectroscopy of low-grade metamorphic volcanic rocks of the Pilbara Craton

    NARCIS (Netherlands)

    Abweny, Mohammad S.; van Ruitenbeek, Frank J A; de Smeth, Boudewijn; Woldai, Tsehaie; van der Meer, Freek D.; Cudahy, Thomas; Zegers, Tanja; Blom, Jan Kees; Thuss, Barbara

    This paper shows the results of Short-Wavelength Infrared (SWIR) spectroscopy investigations of volcanic rocks sampled from low-grade metamorphic greenstone belts of the Archean Pilbara Craton in Western Australia. From the reflectance spectra a range of spectrally active minerals were identified,

  11. The Lu-Hf isotope composition of cratonic lithosphere: disequilibrium between garnet and clinopyroxene in kimberlite xenoliths

    NARCIS (Netherlands)

    Simon, N.S.C.; Carlson, R.W.; Pearson, D.G.; Davies, G.R.

    2002-01-01

    12th Annual V.M. Goldschmidt Conference Davos Switzerland, The Lu-Hf isotope composition of cratonic lithosphere: disequilibrium between garnet and clinopyroxene in kimberlite xenoliths (DTM, Carnegie Institution of Washington), Pearson, D.G. (University of Durham)

  12. Surface Curvature in Island Groups and Discontinuous Cratonic Structures

    Science.gov (United States)

    McDowell, M. S.

    2002-05-01

    The Canadian Archipelago includes eight major islands and a host of smaller ones. They are separated by water bodies, of varying widths attributable to glacial activity and ocean currents. Land form varies from relatively rugged mountains (~2000 m) in eastern, glacial, islands, to low lying western, similar to the continental topography adjacent. The Arctic region is thought to have been low average elevation before the Pleistocene. To a picture puzzler, it all looks like it fit together. Experimentally cutting apart the islands from large scale maps shows that the rough edges match fairly well. However, when those independent pieces are sutured together, without restraint, as in free air, the fit is far better. Far more importantly, they consistently form a noticeably concave surface. This tendency is not at all apparent in flat surface or computer screen manipulation; the pieces need to be "hand joined" or on a molded surface to allow the assembly to freely form as it will. Fitting together the coastlines above 60 \\deg north, from 120 \\deg west to 45 \\deg east, and comparing the resulting contracted area to the original, obtains an 8 percent area reduction. The curvature "humps" a trial planar section of 15 cms by 1.6 cm, a substantial difference in the radius of curvature. If you rashly suggest applying that formula globally, the resulting sphere would have a surface area of 4.7 x108,(down from 5 x108), and therefore radius of 6117 km, down from 6400, which is a rather preposterous conclusion. As nobody would believe it, I tested the idea elsewhere. The Huronian succession of six named cratons is adjacent on the south. I cut this map apart, too, and fit it together, once again getting a curvature, this time more pronounced. I am trying it with the Indonesian Archipelago, although this area has volcanic complications, and with Precambrian Basins in western Australia and Nimibia, Africa. Indications are - an essentially similar pattern of fit, but non uniform

  13. Palaeomagnetism of neoproterozoic formations in the volta basin ...

    African Journals Online (AJOL)

    The Volta basin lies on the southern part of the West African craton, more precisely on the Leo (or Man) craton. The Dahomeyides chain is thrust onto its eastern fringe. The Volta basin is filled with Neoproterozoic to Cambro- Ordovician sediments. From bottom to top they are: the Boumbouaka Supergroup made of ...

  14. Archaean ultra-depleted komatiites formed by hydrous melting of cratonic mantle.

    Science.gov (United States)

    Wilson, A H; Shirey, S B; Carlson, R W

    2003-06-19

    Komatiites are ultramafic volcanic rocks containing more than 18 per cent MgO (ref. 1) that erupted mainly in the Archaean era (more than 2.5 gigayears ago). Although such compositions occur in later periods of Earth history (for example, the Cretaceous komatiites of Gorgona Island), the more recent examples tend to have lower MgO content than their Archaean equivalents. Komatiites are also characterized by their low incompatible-element content, which is most consistent with their generation by high degrees of partial melting (30-50 per cent). Current models for komatiite genesis include the melting of rock at great depth in plumes of hot, diapirically rising mantle or the melting of relatively shallow mantle rocks at less extreme, but still high, temperatures caused by fluxing with water. Here we report a suite of ultramafic lava flows from the Commondale greenstone belt, in the southern part of the Kaapvaal Craton, which represents a previously unrecognized type of komatiite with exceptionally high forsterite content of its igneous olivines, low TiO(2)/Al(2)O(3) ratio, high silica content, extreme depletion in rare-earth elements and low Re/Os ratio. We suggest a model for their formation in which a garnet-enriched residue left by earlier cratonic volcanism was melted by hydration from a subducting slab.

  15. THE STRUCTURE OF THE LITHOSPHERIC MANTLE OF THE SIBERAIN CRATON AND SEISMODYNAMICS OF DEFORMATION WAVES IN THE BAIKAL SEISMIC ZONE

    Directory of Open Access Journals (Sweden)

    A. A. Stepashko

    2013-01-01

    Full Text Available  The evolution and specific features of seismogynamics of the Baikal zones are reviewed in the context of interactions between deep deformation waves and the regional structure of the lithospheric mantle. The study is based on a model of the mantle structure with reference to chemical compositions of mantle peridotites from ophiolotic series located in the south-western framing of the Siberian craton (Fig. 1. The chemical zonation of the lithospheric mantle at the regional scale is determined from results of analyses of the heterogeneity of compositions of peridotites (Fig. 2, Table 1 and variations of contents of whole rock major components, such as iron, magnesium and silica (Fig. 3. According to spatial variations of the compositions of peridotites, the mantle has the concentric zonal structure, and the content of SiO2 is regularly decreasing, while concentrations of FeO∑ and MgO are increasing towards the centre of such structure (Fig. 4. This structure belongs to the mantle of the Siberian craton, which deep edge extends beyond the surface contour of the craton and underlies the north-western segment of the Central Asian orogenic belt.Results of the studies of peridotites of the Baikal region are consistent with modern concepts [Snyder, 2002; O’Reilly, Griffin, 2006; Chen et al., 2009] that suggest that large mantle lenses underlie the Archaean cratons (Fig. 5. The lenses are distinguished by high-density ultrabasic rocks and compose high-velocity roots of cratons which have remained isolated from technic processes. Edges of the mantle lenses may extend a few hundred kilometers beyond the limits of the cratons and underlie orogenic belts that frame the cratons, and this takes place in the south-western segment of the Siberian craton.The revealed structure of the lithospheric mantle is consistent with independent results of seismic and magmatectonical studies of the region. The Angara geoblock is located above the central part of the

  16. Abnormal lithium isotope composition from the ancient lithospheric mantle beneath the North China Craton.

    Science.gov (United States)

    Tang, Yan-Jie; Zhang, Hong-Fu; Deloule, Etienne; Su, Ben-Xun; Ying, Ji-Feng; Santosh, M; Xiao, Yan

    2014-03-04

    Lithium elemental and isotopic compositions of olivines in peridotite xenoliths from Hebi in the North China Craton provide direct evidence for the highly variable δ(7)Li in Archean lithospheric mantle. The δ(7)Li in the cores of olivines from the Hebi high-Mg# peridotites (Fo > 91) show extreme variation from -27 to +21, in marked deviation from the δ(7)Li range of fresh MORB (+1.6 to +5.6) although the Li abundances of the olivines are within the range of normal mantle (1-2 ppm). The Li abundances and δ(7)Li characteristics of the Hebi olivines could not have been produced by recent diffusive-driven isotopic fractionation of Li and therefore the δ(7)Li in the cores of these olivines record the isotopic signature of the subcontinental lithospheric mantle. Our data demonstrate that abnormal δ(7)Li may be preserved in the ancient lithospheric mantle as observed in our study from the central North China Craton, which suggest that the subcontinental lithospheric mantle has experienced modification of fluid/melt derived from recycled oceanic crust.

  17. Neoarchean granite-greenstone belts and related ore mineralization in the North China Craton: An overview

    Directory of Open Access Journals (Sweden)

    Li Tang

    2018-05-01

    Full Text Available Tectonic processes involving amalgamations of microblocks along zones of ocean closure represented by granite-greenstone belts (GGB were fundamental in building the Earth's early continents. The crustal growth and cratonization of the North China Craton (NCC are correlated to the amalgamation of microblocks welded by 2.75–2.6 Ga and ∼2.5 Ga GGBs. The lithological assemblages in the GGBs are broadly represented by volcano-sedimentary sequences, subduction-collision related granitoids and bimodal volcanic rocks (basalt and dacite interlayered with minor komatiites and calc-alkalic volcanic rocks (basalt, andesite and felsic rock. The geochemical features of meta-basalts in the major GGBs of the NCC display affinity with N-MORB, E-MORB, OIB and calc-alkaline basalt, suggesting that the microblocks were separated by oceanic realm. The granitoid rocks display arc signature with enrichment of LILE (K, Rb, Sr, Ba and LREE, and depletion of HFSE (Nb, Ta, Th, U, Ti and HREE, and fall in the VAG field. The major mineralization includes Neoarchean BIF-type iron and VMS-type Cu-Zb deposits and these, together with the associated supracrustal rocks possibly formed in back-arc basins or arc-related oceanic slab subduction setting with or without input from mantle plumes. The 2.75–2.60 Ga TTG rocks, komatiites, meta-basalts and metasedimentary rocks in the Yanlingguan GGB are correlated to the upwelling mantle plume with eruption close to the continental margin within an ocean basin. The volcano-sedimentary rocks and granitoid rocks in the late Neoarchean GGBs display formation ages of 2.60–2.48 Ga, followed by metamorphism at 2.52–2.47 Ga, corresponding to a typical modern-style subduction-collision system operating at the dawn of Proterozoic. The late Neoarchean komatiite (Dongwufenzi GGB, sanukitoid (Dongwufenzi GGB and Western Shandong GGB, BIF (Zunhua GGB and VMS deposit (Hongtoushan-Qingyuan-Helong GGB have closer connection to a combined

  18. Genesis of Neoproterozoic granitoid magmatism in the Eastern Aracuai Fold Belt, eastern Brazil: field, geochemical and Sr-Nd isotopic evidence

    International Nuclear Information System (INIS)

    Celino, Joil Jose; Botelho, Nilson Francisquini; Pimentel, Marcio Martins

    2000-01-01

    The Neoproterozoic granitoid magmatism of the Aracuai Fold Belt (AFB) is an important element for the discussion of the evolution of this belt and its relationships with the African counterpart, the West Congo Belt. In the eastern part of the AFB, four different granitoid suites were recognized. The Nanuque Suite (NQS) comprises syn-tectonic peraluminous cordierite-bearing monzogranites. The Sao Paulinho Suite (SPS) consists of Th-rich peraluminous two mica or biotite-only granitoids. Calc-alkalic granitoids with magmatic epidote were grouped into the Itagimirim Suite (ITS) and post-tectonic charnockitic rocks were grouped into the Salomao Suite (SLS). Sm-Nd mineral isochron and Rb- isochron yielded ages of yielded ages of respectively 761 Ma and 714 Ma for the Nanuque and Sao Paulino suites. The general Sr-Nd isotopic characteristics of the granitoid suites and some country rocks indicate that the parental magmas were mostly the product of melting of the Paraiba do Sul metasediments. The chronological and genetic evolution the Neoproterozoic plutonism can be envisaged in a model of est-dipping subduction zone, followed by a continental collision between the Brasiliano/Pan-African (Brazil) and Congo (Africa cratons and final episodes of uplift and collapse. (author)

  19. Timing of mafic magmatism in the Tapajós Province (Brazil) and implications for the evolution of the Amazon Craton: evidence from baddeleyite and zircon U Pb SHRIMP geochronology

    Science.gov (United States)

    Santos, João Orestes Schneider; Hartmann, Léo Afraneo; McNaughton, Neal Jesse; Fletcher, Ian Robert

    2002-09-01

    The precise timing and possible sources of the mafic rocks in the Amazon craton are critical for reconstruction of the Atlantica supercontinent and correlation of mafic magmatism worldwide. New SHRIMP U-Pb baddeleyite and zircon ages and the reinterpretation of 207 existing dates indicate one orogenic (Ingarana) and four postorogenic (Crepori, Cachoeira Seca, Piranhas, and Periquito) basaltic events in the Tapajós Province, south central Amazon craton. Orogenic gabbro dikes that host gold mineralization are 1893 Ma and interpreted as associated with the Ingarana gabbro intrusions of the bimodal calk-alkalic Parauari intrusive suite. The age of 1893 Ma can be used as a guide to discriminate older and mineralized orogenic dikes from younger and nonmineralized Crepori- and Cachoeira Seca-related mafic dikes. The baddeleyite U-Pb age of the postorogenic Crepori dolerite (gabbro-dolerite sills and dikes) is 1780±9 Ma, ˜150 my older than the ages provided by K-Ar. This value correlates well with the Avanavero tholeiitic intrusions in the Roraima group, in the northern part of the craton in Guyana, Venezuela, and Roraima in Brazil. Early Statherian tholeiitic magmatism was widespread not only in the Amazon craton, but also in the La Plata craton of southern South America, where it is known as the giant Piedra Alta swarm of Uruguay and the post-Trans-Amazonian dikes of Tandil in Argentina. The Cachoeira Seca troctolite represents laccoliths, Feixes, and São Domingos, whose baddeleyite U-Pb age is 1186±12 Ma, 120-150 my older than the known K-Ar ages. This age is comparable to other Stenian gabbroic rocks with alkalic affinity in the craton, such as the Seringa Formation in NE Amazonas and the basaltic flows of the Nova Floresta formation in Rondônia. Dolerite from the giant Piranhas dike swarm in the western Tapajós Province has a Middle Cambrian age (507±4 Ma, baddeleyite) and inherited zircons in the 2238-1229 Ma range. The Piranhas dikes fill extensional NNE and

  20. Thermal modeling and geomorphology of the south border of the Sao Francisco Craton: thermochronology by fission tracks in apatites;Modelagem termica e geomorfologia da borda sul do Craton do Sao Francisco: termocronologia por tracos de fissao em apatita

    Energy Technology Data Exchange (ETDEWEB)

    Hackspacher, Peter Christian [UNESP, Rio Claro, SP (Brazil). Inst. de Geociencias e Ciencias Exatas; Godoy, Daniel Francoso de; Franco, Ana Olivia Barufi [UNESP, Rio Claro, SP (Brazil). Pos-Graduacao em Geologia Regional; Ribeiro, Luiz Felipe Brandini [NUCLEARGEO, Rio Claro, SP (Brazil); Hadler Neto, Julio Cesar [Universidade Estadual de Campinas (IFGW/UNICAMP), SP (Brazil). Inst. de Fisica Gleb Wataghin

    2007-12-15

    Recent developments in Fission Track thermochronology associated to mesozoic-cenozoic erosion and tectonic presented trough thematic maps (isotemperature), permit to model the landscape evolution in the southern border of the Sao Francisco craton, southeastern Brazil. Paleotemperature, obtained by fission track analysis in apatite, is closely related to geomorphologic interpretations. The area suffered a complex imprint of endogenous and exogenous processes resulting diversified and differentiated relieves. The landscape is strongly controlled by exhumation between Jurassic and Lower Cretaceous, uplift with tectonic denudation related to crustal heating at the Upper Cretaceous and reactivation of faults until the Miocene. This scenario is a result of reactivations of different brittle structures that accommodate the deformation in the southern border of the Sao Francisco craton. The landscape reflects denudations of up to 3 km with preserved remains of erosive surfaces in the topographical tops and chronocorrelates deposits in the basins of the region. (author)

  1. Electrical Conductivity Model of the Mantle Lithosphere of the Slave Craton (NW Canada) and its tectonic interpretation in the context of Geochemical Results

    Science.gov (United States)

    Lezaeta, P.; Chave, A.; Evans, R.; Jones, A. G.; Ferguson, I.

    2002-12-01

    The Slave Craton, northwestern Canada, contains the oldest known rocks on Earth, with exposed outcrop over an area of about 600x400 km2. The discovery of economic diamondiferous kimberlite pipes during the early 1990s motivated extensive research in the region. Over the last six years, four types of deep-probing magnetotelluric (MT) surveys were conducted within the framework of diverse geoscientific programs, aimed at determining the regional-scale electrical structures of the craton. Two of the surveys involved novel acquisition; one through frozen lake ice along ice roads during winter, and the second deploying ocean-bottom instrumentation from float planes during summer. The latter surveys required one year of recording between summers, thus allowing long period transfer functions that lead to mantle penetration depths of over 300 km. Two-dimensional modeling of the MT data from along the winter road showed the existence of a high conductivity zone at depths of 80-120 km beneath the central Slave craton. This anomalous region is spatially coincident with an ultradepleted harzburgitic layer in the upper mantle that was interpreted by others to be related to a subducted slab emplaced during the mid-Archean. A 3-D electrical conductivity model of the Slave lithosphere has been obtained, by trial and error, to fit the magnetic transfer and MT response functions from the lake experiments. This 3-D model traces the central Slave conductor as a NE-SW oriented mantle structure. Its NE-SW orientation coincides with that of a late fold belt system, with the first phase of craton-wide plutonism at ca 2630-2590 Ma, three-part subdivision of the craton based on SKS results, and with a G10 (garnet) geochemical mantle boundaries. All of these highlight a NE-SW structural grain to the lithospheric mantle of the craton, in sharp contrast to the N-S grain of the crust. Constraints on the depth range and lateral extension of the electrical conductive structure are obtained

  2. Numerical modeling of convective erosion and peridotite-melt interaction in big mantle wedge: Implications for the destruction of the North China Craton

    Science.gov (United States)

    He, Lijuan

    2014-04-01

    The deep subduction of the Pacific Plate underneath East Asia is thought to have played a key role in the destruction of the North China Craton (NCC). To test this hypothesis, this paper presents a new 2-D model that includes an initial stable equilibrated craton, the formation of a big mantle wedge (BMW), and erosion by vigorous mantle convection. The model shows that subduction alone cannot thin the cold solid craton, but it can form a low-viscosity BMW. The amount of convective erosion is directly proportional to viscosity within the BMW (η0bmw), and the rheological boundary layer thins linearly with decreasing log10(η0bmw), thereby contributing to an increase in heat flow at the lithospheric base. This model also differs from previous modeling in that the increase in heat flow decays linearly with t1/2, meaning that the overall thinning closely follows a natural log relationship over time. Nevertheless, convection alone can only cause a limited thinning due to a minor increase in basal heat flow. The lowering of melting temperature by peridotite-melt interaction can accelerate thinning during the early stages of this convection. The two combined actions can thin the craton significantly over tens of Myr. This modeling, combined with magmatism and heat flow data, indicates that the NCC evolution has involved four distinct stages: modification in the Jurassic by Pacific Plate subduction and BMW formation, destruction during the Early Cretaceous under combined convective erosion and peridotite-melt interaction, extension in the Late Cretaceous, and cooling since the late Cenozoic.

  3. Genesis of the Hengling magmatic belt in the North China Craton: Implications for Paleoproterozoic tectonics

    Science.gov (United States)

    Peng, Peng; Guo, Jinghui; Zhai, Mingguo; Windley, Brian F.; Li, Tiesheng; Liu, Fu

    2012-09-01

    The 2200-1880 Ma igneous rocks in the central and eastern parts of the North China Craton (NCC) constitute a new Hengling magmatic belt (HMB), which includes the ~ 2147 Ma Hengling mafic sill/dyke swarm, the ~ 2060 Ma Yixingzhai mafic dyke swarm, and the ~ 1973 Ma Xiwangshan mafic dyke swarm. The three swarms are contiguous and have experienced variable degrees of metamorphism from greenschist to low amphibolite facies (Hengling), medium granulite facies (Yixingzhai), and medium/high-pressure granulite facies (Xiwangshan). They are all tholeiitic in composition typically with 47-52 wt.% SiO2 and 4-10 wt.% MgO, and all show light rare earth element enrichments and Nb- and Ta-depletion. Their Nd TDM ages are in the range of 2.5-3.0 Ga. Specifically, the Hengling and Yixingzhai dykes/sills are depleted in Th, U, Zr, Hf and Ti, whereas the Xiwangshan dykes are enriched in U and weakly depleted in other elements. Variable Sr-anomalies indicate significant feldspar accumulation (positive anomalies) or fractionation. The ɛNd(t) values of the three swarms are: - 3.2-+3.0 (Hengling), - 1.7-+ 1.8 (Yixingzhai) and - 1.4-+ 1.0 (Xiwangshan). These mafic representatives of the HMB originated from the > 2.5 Ga sub-continental lithospheric mantle of the NCC, and with A-type granites and other igneous associations in this belt they likely evolved in an intra-continental rift. The progressive changing compositions of the three swarms are interpreted in terms of their source regions at different depths, i.e., shallower and shallower through time. And the decrease in scale and size of the intrusions and their magma volumes indicate the progressive weakening of magmatism in this rift. The rocks in this belt are different chronologically, petrologically and chemically from those in the Xuwujia magmatic belt (XMB). We propose that the two magmatic belts represent two different magmatic systems in different blocks of the NCC, i.e., an eastern block (with the HMB) and a western block

  4. Compositional trends among Kaapvaal Craton garnet peridotite xenoliths and their effects on seismic velocity and density

    DEFF Research Database (Denmark)

    Schutt, Derek; Lesher, Charles

    2010-01-01

    and clinopyroxene enrichment possibly as a consequence of melt infiltration. More than half of the mineral mode variance among Kaapvaal Craton xenoliths can be accounted for by opx enrichment. Melt depletion effects can account for as much as 30% of the variance, while less than 20% of the variance is associated...

  5. Density structure of the cratonic mantle in southern Africa

    DEFF Research Database (Denmark)

    Artemieva, Irina; Vinnik, Lev P.

    2016-01-01

    contributions of the both factors to surface topography in the cratons of southern Africa. Our analysis takes advantage of the SASE seismic experiment which provided high resolution regional models of the crustal thickness.We calculate the model of density structure of the lithospheric mantle in southern Africa...... that mantle residual (dynamic) topography may be associated with the low-density region below the depth of isostatic compensation. A possible candidate is the low velocity layer between the lithospheric base and the mantle transition zone, where a temperature anomaly of 100-200. °C in a ca. 100-150. km thick...... layer may explain the observed reduction in Vs velocity and may produce ca. 0.5-1.0. km to the regional topographic uplift....

  6. Structures, microfabrics, fractal analysis and temperature-pressure estimation of the Mesozoic Xingcheng-Taili ductile shear zone in the North China craton

    Science.gov (United States)

    Liang, Chenyue; Neubauer, Franz; Liu, Yongjiang; Jin, Wei; Zeng, Zuoxun; Bernroider, Manfred; Li, Weimin; Wen, Quanbo; Han, Guoqing; Zhao, Yingli

    2014-05-01

    The ductile shear zone in Xingcheng-Taili area (western Liaoning Province in China) is tectonically located in the eastern section of the northern margin of the North China craton, and dominantly comprises deformed granitic rocks of Neoarchean and Triassic to Late Jurassic age, which were affected by shearing within middle- to low-grade metamorphic conditions. Because a high-temperature metamorphic overprint is lacking, microstructures attesting to low-temperature ductile deformation are well preserved. However, the rocks and its structures have not been previously analyzed in detail except by U-Pb zircon dating and some geochemistry. Here, we describe the deformation characteristics and tectonic evolution of the Xingcheng-Taili ductile shear zone, in order to understand the mode of lithosphericscale reactivation, extension and thinning of the North China craton. The ductile deformation history comprises four successive deformation phases: (1) In the Neoarchean granitic rocks, a steep gneissosity and banded structures trend nearly E-W (D1). (2) A NE-striking sinistral structure of Upper Triassic rocks may indicate a deformation event (D2) in Late Triassic times, which ductile deformation structures superimposed on Neoarchean granitic rocks. (3) A gneissose structure with S-C fabrics as well as an ENE-trending sinistral strike-slip characteristic (D3) developed in Upper Jurassic biotite adamellite and show the deformation characteristics of a shallow crustal level and generated mylonitic fabrics superimposed on previous structures. (4) Late granitic dykes show different deformational behavior, and shortening with D4 folds. The attitude of the foliation S and mineral stretching lineation of three main types of rocks shows remarkable differences in orientation. The shapes of recrystallized quartz grains from three main types of granitic rocks with their jagged and indented boundaries were natural records of deformation conditions (D1to D3). Crystal preferred

  7. Formation and temporal evolution of the Kalahari sub-cratonic lithospheric mantle: Constraints from Venetia xenoliths, South Africa

    NARCIS (Netherlands)

    Hin, R.C.; Morel, M.L.A.; Nebel, O.; Mason, P.R.D.; van Westrenen, W.; Davies, G.R.

    2009-01-01

    The ~533 Ma Venetia Diamond Mine is located between the Kaapvaal and Zimbabwe Cratons and the study of selected xenoliths provides the opportunity to investigate the temporal evolution of the sub-continental lithospheric mantle (SCLM) underneath southern Africa, as well as the extent and potentially

  8. Buried paleo-sedimentary basins in the north-eastern Black Sea-Azov Sea area and tectonic implications (DOBRE-2)

    Science.gov (United States)

    Starostenko, Vitaly; Stephenson, Randell; Janik, Tomasz; Tolkunov, Anatoly

    2014-05-01

    A number of independent but inter-related projects carried out under the auspices of various national and international programmes in Ukraine including DARIUS were aimed at imaging the upper lithosphere, crustal and sedimentary basin architecture in the north-eastern Black Sea, southern Crimea and Kerch peninsulas and the Azov Sea. This region marks the transition from relatively undisturbed Precambrian European cratonic crust and lithosphere north of the Azov Sea to areas of significant Phanerozoic tectonics and basin development, in both extensional as well as compressional environments, to the south, including the eastern Black Sea rift, which is the main sedimentary basin of the study area. The wide-angle reflection and refraction (WARR) profile DOBRE-2, a Ukrainian national project with international participation (see below), overlapping some 115 km of the southern end of the DOBREfraction'99 profile (that crosses the intracratonic Donbas Foldbelt) in the north and running to the eastern Black Sea basin in the south, utilised on- and offshore recording and energy sources. It maps crustal velocity structure across the craton margin and documents, among other things, that the Moho deepens from 40 km to ~47 km to the southwest below the Azov Sea and Crimean-Caucasus deformed zone. A regional CDP seismic profile coincident with DOBRE-2, crossing the Azov Sea, Kerch Peninsula and the north-eastern Black Sea southwest to the Ukraine-Turkey border, acquired by Ukrgeofisika (the Ukrainian national geophysical company) reveals in its inferred structural relationships the ages of Cretaceous and younger extensional and subsequent basin inversion tectonic events as well as the 2D geometry of basement displacement associated with post mid-Eocene inversion. A direct comparison of the results of the WARR velocity model and the near-vertical reflection structural image has been made by converting the former into the time domain. The results dramatically demonstrate that

  9. East-China Geochemistry Database (ECGD):A New Networking Database for North China Craton

    Science.gov (United States)

    Wang, X.; Ma, W.

    2010-12-01

    North China Craton is one of the best natural laboratories that research some Earth Dynamic questions[1]. Scientists made much progress in research on this area, and got vast geochemistry data, which are essential for answering many fundamental questions about the age, composition, structure, and evolution of the East China area. But the geochemical data have long been accessible only through the scientific literature and theses where they have been widely dispersed, making it difficult for the broad Geosciences community to find, access and efficiently use the full range of available data[2]. How to effectively store, manage, share and reuse the existing geochemical data in the North China Craton area? East-China Geochemistry Database(ECGD) is a networking geochemical scientific database system that has been designed based on WebGIS and relational database for the structured storage and retrieval of geochemical data and geological map information. It is integrated the functions of data retrieval, spatial visualization and online analysis. ECGD focus on three areas: 1.Storage and retrieval of geochemical data and geological map information. Research on the characters of geochemical data, including its composing and connecting of each other, we designed a relational database, which based on geochemical relational data model, to store a variety of geological sample information such as sampling locality, age, sample characteristics, reference, major elements, rare earth elements, trace elements and isotope system et al. And a web-based user-friendly interface is provided for constructing queries. 2.Data view. ECGD is committed to online data visualization by different ways, especially to view data in digital map with dynamic way. Because ECGD was integrated WebGIS technology, the query results can be mapped on digital map, which can be zoomed, translation and dot selection. Besides of view and output query results data by html, txt or xls formats, researchers also can

  10. Lithospheric expression of geological units in central and eastern North America from full waveform tomography

    Science.gov (United States)

    Yuan, Huaiyu; French, Scott; Cupillard, Paul; Romanowicz, Barbara

    2014-09-01

    The EarthScope TA deployment has provided dense array coverage throughout the continental US and with it, the opportunity for high resolution 3D seismic velocity imaging of both lithosphere and asthenosphere in the continent. Building upon our previous long-period waveform tomographic modeling in North America, we present a higher resolution 3D isotropic and radially anisotropic shear wave velocity model of the North American lithospheric mantle, constructed tomographically using the spectral element method for wavefield computations and waveform data down to 40 s period. The new model exhibits pronounced spatial correlation between lateral variations in seismic velocity and anisotropy and major tectonic units as defined from surface geology. In the center of the continent, the North American craton exhibits uniformly thick lithosphere down to 200-250 km, while major tectonic sutures of Proterozoic age visible in the surface geology extend down to 100-150 km as relatively narrow zones of distinct radial anisotropy, with Vsv >Vsh. Notably, the upper mantle low velocity zone is present everywhere under the craton between 200 and 300 km depth. East of the continental rift margin, the lithosphere is broken up into a series of large, somewhat thinner (150 km) high velocity blocks, which extend laterally 200-300 km offshore into the Atlantic Ocean. Between the craton and these deep-rooted blocks, we find a prominent narrow band of low velocities that roughly follows the southern and eastern Laurentia rift margin and extends into New England. We suggest that the lithosphere along this band of low velocities may be thinned due to the combined effects of repeated rifting processes and northward extension of the hotspot related Bermuda low-velocity channel across the New England region. We propose that the deep rooted high velocity blocks east of the Laurentia margin represent the Proterozoic Gondwanian terranes of pan-African affinity, which were captured during the Rodinia

  11. The 3.26-3.24 Ga Barberton asteroid impact cluster: Tests of tectonic and magmatic consequences, Pilbara Craton, Western Australia

    Science.gov (United States)

    Glikson, Andrew; Vickers, John

    2006-01-01

    The location in the Barberton Greenstone Belt (Kaapvaal Craton) of ∼3.26-3.24 Ga asteroid impact ejecta units at, and immediately above, a sharp break between a > 12 km-thick mafic-ultramafic volcanic crust (Onverwacht Group ∼3.55-3.26 Ga, including the ∼3.298 > 3.258 Ga Mendon Formation) and a turbidite-felsic volcanic rift-facies association (Fig Tree Group ∼3.258-3.225 Ga), potentially represents the first documented example of cause-effect relations between extraterrestrial bombardment and major tectonic and igneous events [D.R. Lowe, G.R. Byerly, F. Asaro, F.T. Kyte, Geological and geochemical record of 3400 Ma old terrestrial meteorite impacts, Science 245 (1989) 959-962; D.R. Lowe, G.R. Byerly, F.T. Kyte, A. Shukolyukov, F. Asaro, A. Krull, Spherule beds 3.47-3.34 Ga-old in the Barberton greenstone belt, South Africa: a record of large meteorite impacts and their influence on early crustal and biological evolution, Astrobiology 3 (2003) 7-48; A.Y. Glikson, The astronomical connection of terrestrial evolution: crustal effects of post-3.8 Ga mega-impact clusters and evidence for major 3.2 ± 0.1 Ga bombardment of the Earth-Moon system, J. Geodyn. 32 (2001) 205-229]. Here we correlate this boundary with a contemporaneous break and peak magmatic and faulting events in the Pilbara Craton, represented by the truncation of a 3.255-3.235 Ga-old volcanic sequence (Sulphur Springs Group-SSG) by a turbidite-banded iron formation-felsic volcanic association (Pincunah Hill Formation, basal Gorge Creek Group). These events are accompanied by ∼3.252-3.235 Ga granitoids (Cleland plutonic suite). The top of the komatiite-tholeiite-rhyolite sequence of the SSG is associated with a marker chert defined at 3.238 ± 3-3.235 ± 3 Ga, abruptly overlain by an olistostrome consisting of mega-clasts of felsic volcanics, chert and siltstone up to 250 × 150 m-large, intercalated with siliciclastic sedimentary rocks and felsic volcanics (Pincunah Hill Formation-basal Gorge

  12. Komatiites and nickel sulphide orebodies of the Black Swan area, Yilgarn Craton, Western Australia. 1. Petrology and volcanology of host rocks

    Science.gov (United States)

    Hill, R. E. T.; Barnes, S. J.; Dowling, S. E.; Thordarson, T.

    2004-11-01

    The Black Swan Succession is a bimodal association of dacitic and komatiitic volcanic rocks located about 50 km NNE of Kalgoorlie, within the 2.7-Ga Eastern Goldfields greenstone province of the Yilgarn Craton. The komatiite stratigraphy comprises a steep dipping, east facing package about 700 m in maximum thickness and about 2.5 km in strike length (Fig. 1), which hosts a number of economically exploitable Ni sulphide orebodies including the Silver Swan massive ore shoot (approximately half a million tonnes at about 10.5% Ni). The sequence can be subdivided into a Lower Felsic Unit, comprising coherent and autobrecciated facies of multiple dacite lava flows; an upper Eastern and lower Western Ultramafic Unit, each showing marked lateral facies variation, and an Upper Felsic Unit coeval with the Eastern Ultramafic Unit. The komatiite sequence has been metamorphosed at sub-greenschist facies in the presence of high proportions of CO2-rich fluid, giving rise to pervasive talc carbonate and talc carbonate quartz assemblages, with extensive preservation of pseudomorphed igneous textures. Cores of lizardite serpentinite are present in the thickest parts of the ultramafic succession. The degree of penetrative deformation is generally very low, and original stratigraphic relationships are largely intact in much of the sequence. The Eastern Ultramafic Unit and Western Ultramafic Unit are interpreted as components of a single large komatiite flow field, representing overlapping stages in the emplacement of a series of distributory lava pathways and flanking sheet flows. The Western Ultramafic Unit which hosts the bulk of the high-grade massive and disseminated ores is a sequence dominated by coarse-grained olivine cumulates, 2 km wide and up to 500 m thick, with major magma pathways represented by thick, homogenous olivine mesocumulate piles at its northern and southern ends: respectively 400 and 200 m thick. The sequence between the two major pathways consists of olivine

  13. Sequence stratigraphy of the Upper Cambrian (Furongian; Jiangshanian and Sunwaptan) Tunnel City Group, Upper Mississippi Valley: Transgressing assumptions of cratonic flooding

    Science.gov (United States)

    Eoff, Jennifer D.

    2014-01-01

    New data from detailed measured sections permit comprehensive analysis of the sequence framework of the Furongian (Upper Cambrian; Jiangshanian and Sunwaptan stages) Tunnel City Group (Lone Rock Formation and Mazomanie Formation) of Wisconsin and Minnesota. The sequence-stratigraphic architecture of the lower part of the Sunwaptan Stage at the base of the Tunnel City Group, at the contact between the Wonewoc Formation and Lone Rock Formation, records the first part of complex polyphase flooding (Sauk III) of the Laurentian craton, at a scale smaller than most events recorded by global sea-level curves. Flat-pebble conglomerate and glauconite document transgressive ravinement and development of a condensed section when creation of accommodation exceeded its consumption by sedimentation. Thinly-bedded, fossiliferous sandstone represents the most distal setting during earliest highstand. Subsequent deposition of sandstone characterized by hummocky or trough cross-stratification records progradational pulses of shallower, storm- and wave-dominated environments across the craton before final flooding of Sauk III commenced with carbonate deposition during the middle part of the Sunwaptan Stage. Comparison of early Sunwaptan flooding of the inner Laurentian craton to published interpretations from other parts of North America suggests that Sauk III was not a single, long-term accommodation event as previously proposed.

  14. Major element composition of the lithospheric mantle under the North Atlantic craton

    DEFF Research Database (Denmark)

    Bizzarro, Martin; Stevenson, R.K.

    2003-01-01

    nature of the Sarfartoq mantle showing comparable degrees of depletion to other cratonic roots. Modal analyses indicate that the Sarfartoq mantle is not typified by the orthopyroxene enrichment observed in the Kaapvaal root, but shows more affinity with the Canadian Arctic (Somerset Island), Tanzania...... is compositionally layered as follows: (1) an internally stratified upper layer (70 to 180 km) consisting of coarse, un-deformed, refractory garnet-bearing and garnet-free peridotites and, (2) a lower layer (180 to 225 km) characterized by fertile, CPX-bearing, porphyroclastic garnet lherzolites. The stratification...

  15. Intraplate Earthquakes and Deformation within the East Antarctic Craton

    Science.gov (United States)

    Lough, A. C.; Wiens, D.; Nyblade, A.

    2017-12-01

    The apparent lack of tectonic seismicity within Antarctica has long been discussed. Explanations have ranged from a lack of intraplate stress due to the surrounding spreading ridges and low absolute plate velocity (Sykes, 1978), to the weight of ice sheets increasing the vertical normal stress (Johnston, 1987). The 26 station GAMSEIS/AGAP array deployed in East Antarctica from late 2008 to early 2010 provides the first opportunity to study the intraplate seismicity of the Antarctic interior using regional data. Here we report 27 intraplate tectonic earthquakes that occurred during 2009. Depth determination together with their corresponding uncertainty estimates, show that most events originate in the shallow to middle crust, indicating a tectonic and not a cryoseismic origin. The earthquakes are primarily located beneath linear alignments of basins adjacent to the Gamburtsev Subglacial Mountains (GSM) that have been denoted as the East Antarctic rift system (Ferraccioli et al, 2011). The geophysical properties of the `rift' system contrast sharply with those of the GSM and Vostok Subglacial Highlands on either side. Crustal thickness, seismic velocity, and gravity anomalies all indicate large lateral variation in lithospheric properties. We propose the events outline an ancient continental rift, a terrain boundary feature, or a combination of the two where rifting exploited pre-existing weakness. It is natural to draw parallels between East Antarctica and the St. Lawrence depression where rifting and a collisional suture focus intraplate earthquakes within a craton (Schulte and Mooney, 2005). We quantify the East Antarctic seismicity by developing a frequency-magnitude relation, constraining the lower magnitudes with the 2009 results and the larger magnitudes with 1982-2012 teleseismic seismicity. East Antarctica and the Canadian Shield show statistically indistinguishable b-values (near 1) and seismicity rates as expressed as the number of events with mb > 4 per

  16. Time constraint based on zircon dating for the Jacareacanga group (Tapajos province, Amazon craton, Brazil)

    International Nuclear Information System (INIS)

    Almeida, M.E.; Ferreira, A.L; Macambira, M.J.B.; Sachett, C.R

    2001-01-01

    During long time the Jacareacanga meta-volcano sedimentary sequence have been interpreted as Archean greenstone belt terrain. However, recent data are indicating younger U-Pb ages about 2.1 Ga. In the Tapajos Province (Amazon Craton), the Cuiu-Cuiu Complex (2.00-2.03 Ga), Creporizao granitoids (1.99-1.96 Ga) and Jacareacanga Group are the oldest rocks. The Jacareancaga Group is composed by quartzmica schists, quartzites, ferruginous quartzite, metachert, and minor talc-tremolite-chlorite schist, actinolite-epidote schist, hornfels, metargilites and metawackes metamorphosed in low to medium-grade conditions. The aim of the present paper is to estabilish the maximum age of Jacareacanga sedimentation and identify probable sources in Espirito Santo region (Espirito Santo muscovite-biotite schist). In this research, similar and new results are obtained by zircon evaporation methodology. This research shows geochronological data about the Espirito Santo muscovite-biotite schist related to Jacareacanga Group (Ferreira et al., 2000) in Tapajos Province (Amazon Craton). The area is located near Amazonas and Para States boundary (Northern Brazil) and the sample was obtained at Espirito Santo (garimpo) small-scale gold mine (06 o 00min.48seg.S,58 o 08min.17seg.W) (au)

  17. Archean crustal growth of the Imataca complex, Amazonian craton: Evidence from U-Pb-Sm-Nd and Rb-Sr geochronology

    International Nuclear Information System (INIS)

    Tassinari, C.C.G.; Teixeira, W; Nutman, A.P; Szabo, G.; Mondin, M.; Sato, K; Santos, A.P; Siso, C.S

    2001-01-01

    The Archean Imataca Complex (IC), NW Amazonian Craton, forms a ENE-trending, fault-bounded block adjacent to the Paleoproterozoic Maroni-Itacai as magmatic arc (2.2 2.0 Ga) (Tassinari and Macambira, 1999). The IC rocks are complexely deformed, exhibiting elongated and symmetrical domes and thrusts combined with isoclinal folds. Transcurrent faults are also important, like the Guri Fault System - a zone of multiple faulting, shearing and mylonitization along the southeastern edge of the IC. In a pre-Pangean reconstruction using paleomagnetic data from rocks of the African counterpart, the Guri System is contiguous to the Sassandra (Ivory coast) and Zednes (Mauritaine) faults, in agreement also with the comparable geologic evolution between the NW Amazonian and the West Africa cratons, during the Archean and Late-Paleoproterozoic. The IC mainly composed of medium- to high grade quartz-feldspathic paragneiss, exhibits extensive mortar, augen, flaser and mylonitic textures. Calc-alkaline gneiss and granitoid rocks of igneous protolith are also present in the IC, as well as dolomitic marbles, orthopyroxene and magnetite quartzites, and BIFs that include huge ore deposits of Algoma type. Moreover, migmatite injections and anatexis (devoid of metasedimentary components) are widespread in the western part of Complex, the largest migmatite mass centered in Cerro La Ceiba. This paper reports zircon U-Pb SHRIMP, Sm-Nd and Rb-Sr isotopic data of different IC rocks in order to investigate their age and geological evolution within the tectonic framework of the Amazonian Craton (au)

  18. Bouguer images of the North American craton and its structural evolution

    Science.gov (United States)

    Arvidson, R. E.; Bowring, S.; Eddy, M.; Guinness, E.; Leff, C.; Bindschadler, D.

    1984-01-01

    Digital image processing techniques have been used to generate Bouguer images of the North American craton that diplay more of the granularity inherent in the data as compared with existing contour maps. A dominant NW-SE linear trend of highs and lows can be seen extending from South Dakota, through Nebraska, and into Missouri. The structural trend cuts across the major Precambrian boundary in Missouri, separating younger granites and rhyolites from older sheared granites and gneisses. This trend is probably related to features created during an early and perhaps initial episode of crustal assembly by collisional processes. The younger granitic materials are probably a thin cover over an older crust.

  19. Hierarchy of sedimentary discontinuity surfaces and condensed beds from the middle Paleozoic of eastern North America: Implications for cratonic sequence stratigraphy

    Science.gov (United States)

    McLaughlin, P.I.; Brett, Carlton E.; Wilson, M.A.

    2008-01-01

    Sedimentological analyses of middle Paleozoic epeiric sea successions in North America suggest a hierarchy of discontinuity surfaces and condensed beds of increasing complexity. Simple firmgrounds and hardgrounds, which are comparatively ephemeral features, form the base of the hierarchy. Composite hardgrounds, reworked concretions, authigenic mineral crusts and monomictic intraformational conglomerates indicate more complex histories. Polymictic intraformational conglomerates, ironstones and phosphorites form the most complex discontinuity surfaces and condensed beds. Complexity of discontinuities is closely linked to depositional environments duration of sediment starvation and degree of reworking which in turn show a relationship to stratigraphic cyclicity. A model of cratonic sequence stratigraphy is generated by combining data on the complexity and lateral distribution of discontinuities in the context of facies successions. Lowstand, early transgressive and late transgressive systems tracts are representative of sea-level rise. Early and late transgressive systems tracts are separated by the maximum starvation surface (typically a polymictic intraformational conglomerate or condensed phosphorite), deposited during the peak rate of sea-level rise. Conversely the maximum flooding surface, representing the highest stand of sea level, is marked by little to no break in sedimentation. The highstand and falling stage systems tracts are deposited during relative sea-level fall. They are separated by the forced-regression surface, a thin discontinuity surface or condensed bed developed during the most rapid rate of sea-level fall. The lowest stand of sea level is marked by the sequence boundary. In subaerially exposed areas it is occasionally modified as a rockground or composite hardground.

  20. Distribution and Diversity of Carboniferous and Permian Colonial Rugose Coral Faunas in Western North America: Clues for Placement of Allochthonous Terranes

    Directory of Open Access Journals (Sweden)

    Calvin H. Stevens

    2012-05-01

    Full Text Available Colonial rugose corals are common in western cratonal North America and in some of the allochthonous terranes, now amalgamated against its western margin. Throughout the Late Paleozoic, the coral faunas in these two different settings were significantly different. Comparisons of these faunas suggest that during the Mississippian the Alexander terrane probably was southwest of Arctic Alaska and the Stikine terrane probably lay west of the southern part of the North American craton. The Cache Creek terrane lay far out in the Paleopacific Ocean. The Pennsylvanian faunas suggest that the Quesnellia and Eastern Klamath terranes were situated southwest of Arctic Alaska and the Alexander terrane was somewhat farther southwest and farther from cratonal North America. The Stikine terrane continued to be positioned west of the southern part of the North American craton. During the Early Permian, terranes with a cratonal faunal aspect may have lain 2000–3000 km west of cratonal North America and latitudinally generally southwest of their present positions. In the Middle Permian these terranes were carried southward relative to the North American craton. Simultaneously the Tethyan Realm expanded eastward.

  1. Kanfenggou UHP Metamorphic Fragment in Eastern Qinling Orogen and Its Relationship to Dabie-Sulu UHP and HP Metamorphic Belts, Central China

    Institute of Scientific and Technical Information of China (English)

    Suo Shutian; Zhong Zengqiu; Zhou Hanwen; You Zhendong

    2003-01-01

    In the Central Orogenic Belt, China, two UHP metamorphic belts are discriminated mainly based on a detailed structural analysis of the Kanfenggou UHP metamorphic fragment exposed in the eastern Qinling orogen, and together with previous regional structural, petrological and geochronological data at the scale of the orogenic domain. The first one corresponds to the South Altun-North QaidamNorth Qinling UHP metamorphic belt. The other is the Dabie-Sulu UHP and HP metamorphic belts. The two UHP metamorphic belts are separated by a series of tectonic slices composed by the Qinling rock group, Danfeng rock group and Liuling or Foziling rock group etc. respectively, and are different in age of the peak UHP metamorphism and geodynamic implications for continental deep subduction and collision. Regional field and petrological relationships suggest that the Kanfenggou UHP metamorphic fragment that contains a large volume of the coesite- and microdiamond-bearing eclogite lenses is compatible with the structures recognized in the South Altun and North Qaidam UHP metamorphic fragments exposed in the western part of China, thereby forming a large UHP metamorphic belt up to 1 000 km long along the orogen strike. This UHP metamorphic belt represents an intercontinental deep subduction and collision belt between the Yangtze and Sino-Korean cratons, occurred during the Paleozoic. On the other hand, the well-constrained Dabie-Sulu UHP and HP metamorphic belts occurred mainly during Triassic time (250-220 Ma), and were produced by the intrucontinental deep subduction and collision within the Yangtze craton. The Kanfenggou UHP metamorphic fragment does not appear to link with the Dabie-Sulu UHP and HP metamorphic belts along the orogen. There is no reason to assume the two UHP metamorphic belts us a single giant deep subduction and collision zone in the Central Orogenic Belt situated between the Yangtze and Sino-Korean cratons. Therefore, any dynamic model for the orogen must account

  2. (142)Nd evidence for an enriched Hadean reservoir in cratonic roots.

    Science.gov (United States)

    Upadhyay, Dewashish; Scherer, Erik E; Mezger, Klaus

    2009-06-25

    The isotope (146)Sm undergoes alpha-decay to (142)Nd, with a half-life of 103 million years. Measurable variations in the (142)Nd/(144)Nd values of rocks resulting from Sm-Nd fractionation could therefore only have been produced within about 400 million years of the Solar System's formation (that is, when (146)Sm was extant). The (142)Nd/(144)Nd compositions of terrestrial rocks are accordingly a sensitive monitor of the main silicate differentiation events that took place in the early Earth. High (142)Nd/(144)Nd values measured in some Archaean rocks from Greenland hint at the existence of an early incompatible-element-depleted mantle. Here we present measurements of low (142)Nd/(144)Nd values in 1.48-gigayear-(Gyr)-old lithospheric mantle-derived alkaline rocks from the Khariar nepheline syenite complex in southeastern India. These data suggest that a reservoir that was relatively enriched in incompatible elements formed at least 4.2 Gyr ago and traces of its isotopic signature persisted within the lithospheric root of the Bastar craton until at least 1.48 Gyr ago. These low (142)Nd/(144)Nd compositions may represent a diluted signature of a Hadean (4 to 4.57 Gyr ago) enriched reservoir that is characterized by even lower values. That no evidence of the early depleted mantle has been observed in rocks younger than 3.6 Gyr (refs 3, 4, 7) implies that such domains had effectively mixed back into the convecting mantle by then. In contrast, some early enriched components apparently escaped this fate. Thus, the mantle sampled by magmatism since 3.6 Gyr ago may be biased towards a depleted composition that would be balanced by relatively more enriched reservoirs that are 'hidden' in Hadean crust, the D'' layer of the lowermost mantle or, as we propose here, also within the roots of old cratons.

  3. U-Pb thermochronology of the lower crust: producing a long-term record of craton thermal evolution

    Science.gov (United States)

    Blackburn, T.; Bowring, S. A.; Mahan, K. H.; Perron, T.; Schoene, B.; Dudas, F. O.

    2010-12-01

    The EarthScope initiative is focused on providing an enhanced view of the North American lithosphere and the present day stress field of the North American continent. Of key interest is the interaction between convecting asthenosphere and the conducting lithospheric mantle that underlie the continents, especially the cold ‘keels’ that underlie Archean domains. Cratonic regions are in general characterized by minimal erosion and or sediment accumulation. The Integration of seismic tomography, and mantle xenolith studies reveal a keel of seismically fast and relatively buoyant and viscous mantle; physical properties that are intimately linked with the long-term stability and topographic expression of the region. Missing from this model of the continental lithosphere is the 4th dimension--time--and along with it our understanding of the long-term evolution of these stable continental interiors. Here we present a thermal record from the North American craton using U-Pb thermochronology of lower crustal xenoliths. The use of temperature sensitive dates on lower crustal samples can produce a unique time-temperature record for a well-insulated and slowly cooling lithosphere. The base of the crust is insulated enough to remain unperturbed by any plausible changes to surface topography, yet unlike the subadjacent lithospheric mantle, contains accessory phases amenable to U-Pb dating (rutile, apatite, titanite). With near steady state temperatures in the lower crust between 400-600 °C, U-Pb thermochronometers with similar average closure temperatures for Pb are perfectly suited to record the long-term cooling of the lithosphere. Xenoliths from multiple depths, and across the craton yield time-temperature paths produced from U-Pb thermochronometers that record extremely slow cooling (<0.25 °C/Ma) over time scales of billions of years. Combining these data with numerical thermal modeling allow constraints to be placed on the dominant heat transfer mechanisms operating

  4. Juvenile crust formation in the Zimbabwe Craton deduced from the O-Hf isotopic record of 3.8-3.1 Ga detrital zircons

    Science.gov (United States)

    Bolhar, Robert; Hofmann, Axel; Kemp, Anthony I. S.; Whitehouse, Martin J.; Wind, Sandra; Kamber, Balz S.

    2017-10-01

    Hafnium and oxygen isotopic compositions measured in-situ on U-Pb dated zircon from Archaean sedimentary successions belonging to the 2.9-2.8 Ga Belingwean/Bulawayan groups and previously undated Sebakwian Group are used to characterize the crustal evolution of the Zimbabwe Craton prior to 3.0 Ga. Microstructural and compositional criteria were used to minimize effects arising from Pb loss due to metamorphic overprinting and interaction with low-temperature fluids. 207Pb/206Pb age spectra (concordance >90%) reveal prominent peaks at 3.8, 3.6, 3.5, and 3.35 Ga, corresponding to documented geological events, both globally and within the Zimbabwe Craton. Zircon δ18O values from +4 to +10‰ point to both derivation from magmas in equilibrium with mantle oxygen and the incorporation of material that had previously interacted with water in near-surface environments. In εHf-time space, 3.8-3.6 Ga grains define an array consistent with reworking of a mafic reservoir (176Lu/177Hf ∼0.015) that separated from chondritic mantle at ∼3.9 Ga. Crustal domains formed after 3.6 Ga depict a more complex evolution, involving contribution from chondritic mantle sources and, to a lesser extent, reworking of pre-existing crust. Protracted remelting was not accompanied by significant mantle depletion prior to 3.35 Ga. This implies that early crust production in the Zimbabwe Craton did not cause complementary enriched and depleted reservoirs that were tapped by later magmas, possibly because the volume of crust extracted and stabilised was too small to influence (asthenospheric) mantle isotopic evolution. Growth of continental crust through pulsed emplacement of juvenile (chondritic mantle-derived) melts, into and onto the existing cratonic nucleus, however, involved formation of complementary depleted subcontinental lithospheric mantle since the early Archaean, indicative of strongly coupled evolutionary histories of both reservoirs, with limited evidence for recycling and lateral

  5. First record of 1.2 Ga quartz dioritic magmatism in the Archaean Yilgarn Craton, Western Australia, and its significance

    Energy Technology Data Exchange (ETDEWEB)

    Qiu, Y.; McNaughton, N.J.; Groves, D.I.; Dunphy, J.M. [University of Western Australia, Nedlands, WA (Australia). Centre for Strategic Mineral Deposits, Department of Geology and Geophysics

    1999-06-01

    Ion microprobe (SHRIMP) U-Pb zircon dating. Pb-Nd isotope tracer studies and major, trace and rare-earth element analyses have identified, for the first time. a Mesoproterozoic (1.2 Ga) quartz diorite intrusion in the central part of the Archaean Yilgarn Craton. Western Australia The quartz diorite is characterised by intergrowths of quartz and plagioclase, having low A/CNK (0 8). low K{sub 2}O (0.28 wt%), Ba (54 ppm), Rb (11 ppm), Sr (92 ppm), Pb (13 ppm), U (1.7 ppm) and Th (6 ppm) contents, high Nd (41 ppm), Sm (10.5 ppm), Zr (399 ppm). Nb (18.5 ppm). Y (57.5 ppm) and Sc (19 ppm) contents. a low Pb isotope two-stage model {mu} value (6.3), and a primitive initial e{sub Nd} value (+3.4) at 1.2 Ga. It is interpreted that the 1.2 Ga quartz diorite was derived from a predominantly mantle source, with minor crustal contamination, possibly from the surrounding Archaean monzogranites or their source region, during magma ascent. The age (1215 {+-} 11 Ma) of the intrusion overlaps with the timing of a major continental collisional orogeny in the Albany-Fraser Orogen, about 400km south, and is broadly coeval with the diamond-bearing Argyle lamproites in the east Kimberley Block. This study extends the history of granitoid magmatism in the central craton by more than 1.0 billion years (2.6 to 1.2 Ga), and has implications for isotopic data interpretations of tectonothermal events in the craton. Copyright (1999) Blackwell Science Pty Ltd 33 refs., 3 tabs., 6 figs.

  6. A re-evaluation of the Kumta Suture in western peninsular India and its extension into Madagascar

    Science.gov (United States)

    Armistead, Sheree E.; Collins, Alan S.; Payne, Justin L.; Foden, John D.; De Waele, Bert; Shaji, E.; Santosh, M.

    2018-05-01

    It has long been recognised that Madagascar was contiguous with India until the Late Cretaceous. However, the timing and nature of the amalgamation of these two regions remain highly contentious as is the location of Madagascar against India in Gondwana. Here we address these issues with new U-Pb and Lu-Hf zircon data from five metasedimentary samples from the Karwar Block of India and new Lu-Hf data from eight previously dated igneous rocks from central Madagascar and the Antongil-Masora domains of eastern Madagascar. New U-Pb data from Karwar-region detrital zircon grains yield two dominant age peaks at c. 3100 Ma and c. 2500 Ma. The c. 3100 Ma population has relatively juvenile εHf(t) values that trend toward an evolved signature at c. 2500 Ma. The c. 2500 Ma population shows a wide range of εHf(t) values reflecting mixing of an evolved source with a juvenile source at that time. These data, and the new Lu-Hf data from Madagascar, are compared with our new compilation of over 7000 U-Pb and 1000 Lu-Hf analyses from Madagascar and India. We have used multidimensional scaling to assess similarities in these data in a statistically robust way. We propose that the Karwar Block of western peninsular India is an extension of the western Dharwar Craton and not part of the Antananarivo Domain of Madagascar as has been suggested in some models. Based on εHf(t) signatures we also suggest that India (and the Antongil-Masora domains of Madagascar) were palaeogeographically isolated from central Madagascar (the Antananarivo Domain) during the Palaeoproterozoic. This supports a model where central Madagascar and India amalgamated during the Neoproterozoic along the Betsimisaraka Suture.

  7. The extent of the Cratonic keel underneath the Southern African region: A 3D image using Finite-Frequency Tomograph

    DEFF Research Database (Denmark)

    Soliman, Mohammad Youssof Ahmad; Bezada, Max; Thybo, Hans

    2010-01-01

    We have re-examined the P body wave data from the South Africa Seismic Experiment (Carlson et al, EOS 77, 1996) across the Kaapvaal and Zimbabwe cratons and the Bushveld complex. Using finite-frequency kernels, we inverted the P-wave delay times to obtain 3-D images of compressional velocity...

  8. Paleoproterozoic volcanic centers of the São Félix do Xingu region, Amazonian craton, Brazil: Hydrothermal alteration and metallogenetic potential

    Science.gov (United States)

    da Cruz, Raquel Souza; Fernandes, Carlos Marcello Dias; Villas, Raimundo Netuno Nobre; Juliani, Caetano; Monteiro, Lena Virgínia Soares; Lagler, Bruno; Misas, Carlos Mario Echeverri

    2016-06-01

    Geological, petrographic, scanning electron microscopy, and X-ray diffraction studies revealed hydrothermalized lithotypes evidenced by overprinted zones of potassic, propylitic, sericitic, and intermediate argillic alterations types, with pervasive and fracture-controlled styles, in Paleoproterozoic volcano-plutonic units of the São Félix do Xingu region, Amazonian craton, northern Brazil. The Sobreiro Formation presents propylitic (epidote + chlorite + carbonate + clinozoisite + sericite + quartz ± albite ± hematite ± pyrite), sericitic (sericite + quartz + carbonate), and potassic (potassic feldspar + hematite) alterations. The prehnite-pumpellyite pair that is common in geothermal fields also occurs in this unit. The Santa Rosa Formation shows mainly potassic (biotite + microcline ± magnetite), sericitic (sericite + quartz + carbonate ± chlorite ± gold), and intermediate argillic (montmorillonite + kaolinite/halloysite + illite) alterations. These findings strongly suggest the involvement of magma-sourced and meteoric fluids and draw attention to the metallogenetic potential of these volcanic units for Paleoproterozoic epithermal and rare and base metal porphyry-type mineralizations, similar to those already identified in other portions of the Amazonian craton.

  9. Coexistence of enriched and modern-like 142Nd signatures in Archean igneous rocks of the eastern Kaapvaal Craton, southern Africa

    Science.gov (United States)

    Schneider, Kathrin P.; Hoffmann, J. Elis; Boyet, Maud; Münker, Carsten; Kröner, Alfred

    2018-04-01

    The short-lived 146Sm-142Nd isotope system is an important tool for tracing Hadean crust-mantle differentiation processes and constraining their imprint on much younger rocks from Archean cratons. We report the first comprehensive set of high-precision 142Nd analyses for granitoids and amphibolites of the Ancient Gneiss Complex (AGC; Swaziland) and the oldest metavolcanic units of the Barberton Greenstone Belt (BGB; South Africa). The investigated samples span an age range from 3.66 Ga to 3.22 Ga and are representative of major geological units of the AGC and the lower Onverwacht Group of the BGB. Measured samples yielded μ142Nd values in the range from -8 ppm to +3 ppm relative to the JNdi-1 terrestrial standard, with typical errors smaller than 4.4 ppm. The distribution of the μ142Nd values for these 17 measured samples is bimodal with ten samples showing a tendency towards slightly negative μ142Nd anomalies, whereas seven samples have 142Nd similar to the terrestrial reference. The only confidently resolvable μ142Nd anomalies were found in a 3.44 Ga Ngwane Gneiss sample and in amphibolites of the ca. 3.45 Ga Dwalile Greenstone Remnant, revealing μ142Nd values ranging from - 7.9 ± 4.4 to - 6.1 ± 4.3 ppm. The μ142Nd deficits do not correlate with age, lithological unit, or sample locality. Instead, our results reveal that two distinct mantle domains were involved in the formation of the AGC crust. The two reservoirs can be distinguished by their μ142Nd signatures. Mantle-derived rocks tapped the enriched reservoir with negative μ142Nd at least until 3.46 Ga, whereas the granitoids preserved a negative μ142Nd signature that formed by incorporation of older AGC crust at least until 3.22 Ga. The oldest gneisses with no μ142Nd anomaly are up to 3.64 Ga in age, indicating that a modern terrestrial 142Nd reservoir was already present by early Archean times.

  10. Structure of the lithosphere below the southern margin of the East European Craton (Ukraine and Russia) from gravity and seismic data.

    NARCIS (Netherlands)

    Yegorova, T.P.; Stephenson, R.A.; Kostyuchenko, S.L.; Baranova, E.P.; Starostenko, V.I.; Popolitov, K.E.

    2004-01-01

    The present study was undertaken with the objective of deriving constraints from available geological and geophysical data for understanding the tectonic setting and processes controlling the evolution of the southern margin of the East European Craton (EEC). The study area includes the inverted

  11. Introduction to nickel sulfide orebodies and komatiites of the Black Swan area, Yilgarn Craton, Western Australia

    Science.gov (United States)

    Barnes, S. J.

    2004-11-01

    The Black Swan district, 70 km north east of Kalgoorlie in the Archaean Yilgarn Craton of Western Australia, hosts massive and disseminated nickel sulfide orebodies associated with komatiites. The host rocks and ores preserve some remarkable primary igneous features, which provide important clues as to the origin of komatiite-hosted nickel ores. The series of papers that follow report an extremely detailed study of the petrology, volcanology and geochemistry of these unusually well-preserved orebodies and their host rocks.

  12. Infrared spectral and carbon isotopic characteristics of micro- and macro-diamonds from the Panda kimberlite (Central Slave Craton, Canada)

    Science.gov (United States)

    Melton, G. L.; Stachel, T.; Stern, R. A.; Carlson, J.; Harris, J. W.

    2013-09-01

    One hundred and twenty-one micro-diamonds (Panda kimberlite (Ekati mine, Central Slave Craton, Canada) were analyzed for nitrogen content, nitrogen aggregation state (%B) and platelet and hydrogen peak areas (cm- 2). Micro-diamond nitrogen concentrations range from 2‰, but mostly vary by bearing metasomatic fluid/melt that isotopically evolves as it percolates upward through the lithosphere.

  13. Seismic crustal structure of the North China Craton and surrounding area: Synthesis and analysis

    Science.gov (United States)

    Xia, B.; Thybo, H.; Artemieva, I. M.

    2017-07-01

    We present a new digital model (NCcrust) of the seismic crustal structure of the Neoarchean North China Craton (NCC) and its surrounding Paleozoic-Mesozoic orogenic belts (30°-45°N, 100°-130°E). All available seismic profiles, complemented by receiver function interpretations of crustal thickness, are used to constrain a new comprehensive crustal model NCcrust. The model, presented on a 0.25° × 0.25°grid, includes the Moho depth and the internal structure (thickness and velocity) of the crust specified for four layers (the sedimentary cover, upper, middle, and lower crust) and the Pn velocity in the uppermost mantle. The crust is thin (30-32 km) in the east, while the Moho depth in the western part of the NCC is 38-44 km. The Moho depth of the Sulu-Dabie-Qinling-Qilian orogenic belt ranges from 31 km to 51 km, with a general westward increase in crustal thickness. The sedimentary cover is 2-5 km thick in most of the region, and typical thicknesses of the upper crust, middle crust, and lower crust are 16-24 km, 6-24 km, and 0-6 km, respectively. We document a general trend of westward increase in the thickness of all crustal layers of the crystalline basement and as a consequence, the depth of the Moho. There is no systematic regional pattern in the average crustal Vp velocity and the Pn velocity. We examine correlation between the Moho depth and topography for seven tectonic provinces in the North China Craton and speculate on mechanisms of isostatic compensation.

  14. Blueschist facies fault tectonites from the western margin of the Siberian Craton: Implications for subduction and exhumation associated with early stages of the Paleo-Asian Ocean

    Science.gov (United States)

    Likhanov, Igor I.; Régnier, Jean-Luc; Santosh, M.

    2018-04-01

    The tectonic evolution of the Siberian Cratonic margins offers important clues for global paleogeographic reconstructions, particularly with regard to the complex geological history of Central Asia. The Yenisey Ridge fold-and-thrust belt at the western margin of the Siberian Craton forms part of the Central Asian Orogenic Belt (CAOB) and is a key to understand the Precambrian tectonic evolution of the Siberian Craton and crustal growth in the CAOB, the world's largest Phanerozoic accretionary orogenic belt. Here we report for the first time, the occurrence of glaucophane schist relics in tectonites within the Yenisey shear zone which provides insights on Chilean-type convergent boundary. We present results from isotope geochronology (SHRIMP zircon analysis and mica 40Ar/39Ar dating), coupled with P-T calculations derived from conventional geothermobarometry and pseudosections in the system NCKFMASH that suggest two superimposed metamorphic events. During the first stage, glaucophane schists formed at around 640-620 Ma at P-T conditions of 8-10 kbar and 400-450 °C. In the second stage, the rocks experienced dynamic metamorphism (c. 600 Ma) at 11-15 kbar/550-640 °C. The differences in P-T parameters between weakly deformed rocks and intensely deformed tectonites and P-T paths suggest distinct tectonic processes. Geochemical features of the mafic tectonites suggest N-MORB and E-MORB affinity, and the zircon U-Pb ages suggest formation of the protoliths at 701.6 ± 8.4. The sequence of spreading, subduction and shear deformation identified in our study correlate with the early stages of development of the Paleo-Asian Ocean at the western margin of the Siberian Craton and supports the spatial proximity of Siberia and Laurentia at 700-600 Ma, as proposed for the Late Neoproterozoic paleogeographic reconstructions and as robustly constrained from large igneous province (LIP) record.

  15. Reworking of Archean mantle in the NE Siberian craton by carbonatite and silicate melt metasomatism: Evidence from a carbonate-bearing, dunite-to-websterite xenolith suite from the Obnazhennaya kimberlite

    Science.gov (United States)

    Ionov, Dmitri A.; Doucet, Luc S.; Xu, Yigang; Golovin, Alexander V.; Oleinikov, Oleg B.

    2018-03-01

    The Obnazhennaya kimberlite in the NE Siberian craton hosts a most unusual cratonic xenolith suite, with common rocks rich in pyroxenes and garnet, and no sheared peridotites. We report petrographic and chemical data for whole rocks (WR) and minerals of 20 spinel and garnet peridotites from Obnazhennaya with Re-depletion Os isotope ages of 1.8-2.9 Ga (Ionov et al., 2015a) as well as 2 pyroxenites. The garnet-bearing rocks equilibrated at 1.6-2.8 GPa and 710-1050 °C. Some xenoliths contain vermicular spinel-pyroxene aggregates with REE patterns in clinopyroxene mimicking those of garnet. The peridotites show significant scatter of Mg# (0.888-0.924), Cr2O3 (0.2-1.4 wt.%) and high NiO (0.3-0.4 wt.%). None are pristine melting residues. Low-CaO-Al2O3 (≤0.9 wt.%) dunites and harzburgites are melt-channel materials. Peridotites with low to moderate Al2O3 (0.4-1.8 wt.%) usually have CaO > Al2O3, and some have pockets of calcite texturally equilibrated with olivine and garnet. Such carbonates, exceptional in mantle xenoliths and reported here for the first time for the Siberian mantle, provide direct evidence for modal makeover and Ca and LREE enrichments by ephemeral carbonate-rich melts. Peridotites rich in CaO and Al2O3 (2.7-8.0 wt.%) formed by reaction with silicate melts. We infer that the mantle lithosphere beneath Obnazhennaya, initially formed in the Mesoarchean, has been profoundly modified. Pervasive inter-granular percolation of highly mobile and reactive carbonate-rich liquids may have reduced the strength of the mantle lithosphere leading the way for reworking by silicate melts. The latest events before the kimberlite eruption were the formation of the carbonate-phlogopite pockets, fine-grained pyroxenite veins and spinel-pyroxene symplectites. The reworked lithospheric sections are preserved at Obnazhennaya, but similar processes could erode lithospheric roots in the SE Siberian craton (Tok) and the North China craton, where ancient melting residues and

  16. Reassessment of the geologic evolution of selected precambrian terranes in Brazil, based on SHRIMP U-Pb data, part 2: mineiro and Aracuai orogens and Southern Sao Francisco craton; Reavaliacao da evolucao geologica em terrenos pre-cambrianos brasileiros com base em novos dados U-Pb SHRIMP, parte 2: orogeno Aracuai, cinturao mineiro e craton Sao Francisco Meridional

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Luiz Carlos da; Pimentel, Marcio [Brasilia Univ., DF (Brazil). Inst. de Geociencias]. E-mail: luizcarlos@aneel.gov.br; Leite, Carlos Augusto; Vieira, Valter Salino; Silva, Marcio Antonio da; Paes, Vinicius Jose de Castro; Cardoso Filho, Joao Moraes [Companhia de Pesquisas de Recursos Minerais (CPRM), Belo Horizonte, MG (Brazil); Armstrong, Richard [Australian National Univ., Canberra (Australia). Research School of Earth Sciences; Noce, Carlos Mauricio; Pedrosa-Soares, Antonio Carlos [Minas Gerais Univ., Belo Horizonte (Brazil). Inst. de Geociencias. Centro de Pesquisa Manuel Teixeira da Costa; Carneiro, Mauricio Antonio [Ouro Preto Univ., MG (Brazil). Dept. de Geologia

    2002-12-15

    This paper discusses new zircon SHRIMP (Sensitive High Resolution Ion Microprobe) U-Pb geochronological data for 19 key-exposures of several geological units exposed at the eastern border of the Southern Sao Francisco Craton and at the adjacent Proterozoic Mineiro and Aracuai orogens. Samples were collected along several E-W tran sects, aiming at tracing the precise limit of the Sao Francisco Craton Archean basement, as well as assessing the extension of the successive proterozoic orogenic collages. Due to the complex geologic history and/or high grade metamorphism which most of the rock units investigated have undergone, zircon morphology and the U-Pb analytical data exhibit very complex patterns. These are characterized by a combination of inheritance, partial resetting and new zircon growth during high-grade metamorphism. As a consequence, very careful and detailed analyses of cathodoluminescence imagery were required to allow distinction between inheritance, newly melt-precipitated zircon and partially reset zircons, as well as between the ages of magmatic and metamorphic events. In the southeastern border of the craton 5 units yielded Archean crystallization ages ranging from ca. 3000-2700 Ma, with poorly constrained metamorphic ages ranging from ca. 2850 to 550 Ma. The TTG gneissic complex exposed to the east and south of the Quadrilatero Ferrifero, formerly ascribed to the Archean basement, have crystallization ages from ca. 2210 Ma to 2050 Ma, and can now be interpreted as representing pre- to syn-collisional magmatic phases of the Mineiro Belt. Metamorphic ages of ca. 2100 Ma and 560 Ma are also well constrained in zircon populations from these gneisses. The crystallization age of ca 1740 Ma observed for an alkaline granite of the Borrachudos Suite (intrusive into the Archean basement east of the Southern Espinhaco Range) confirmed previous conventional U-Pb data for this Paleoproterozoic rift-related magmatism. One of the major basement inliers within the

  17. Strong crustal seismic anisotropy in the Kalahari Craton based on Receiver Functions

    DEFF Research Database (Denmark)

    Thybo, Hans; Soliman, Mohammad Youssof Ahmad; Artemieva, Irina

    2015-01-01

    Earlier seismic studies of the Kalahari Craton in southern Africa infer deformation of upper mantle by flow with fast direction of seismic anisotropy being parallel to present plate motion, and/or report anisotropy frozen into the lithospheric mantle. We present evidence for very strong seismic...... is uniform within tectonic units and parallel to orogenic strike in the Limpopo and Cape fold belts. It is further parallel to the strike of major dyke swarms which indicates that a large part of the observed anisotropy is controlled by lithosphere fabrics and macroscopic effects. The directions of the fast...... that the crust and lithospheric mantle may have been coupled since cratonisation. If so, the apparent match between mantle anisotropy and the present plate motion is coincidental....

  18. U-Pb SHRIMP and {sup 40}Ar/{sup 39}Ar constraints on the timing of mineralization in the Paleoproterozoic Caxias orogenic gold deposit, Sao Luis cratonic fragment, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Evandro Luiz, E-mail: evandro.klein@cprm.gov.br [Servico Geologico do Brasil (CPRM), Belem, PA (Brazil); Tassinari, Colombo Celso Gaeta, E-mail: ccgtassi@usp.br [Universidade de Sao Paulo (USP), SP (Brazil). Instituto de Geociencias. Centro de Pesquisas Geocronologicas; Vasconcelos, Paulo Marcos, E-mail: paulo@earth.uq.edu.au [University of Queensland, School of Earth Sciences, Brisbane (Australia)

    2014-07-01

    Caxias is an orogenic gold deposit in the Sao Luis cratonic fragment, which is correlated with the Rhyacian terranes of the West-African Craton. The deposit postdates peak metamorphism (estimated at 2100 ± 15 Ma) and is hosted in a shear zone that cuts across schists of the Aurizona Group (2240 ± 5 Ma) and the Caxias Microtonalite. The emplacement age of the microtonalite, as determined in this work by SHRIMP U-Pb zircon dating, is 2009 ± 11 Ma and represents a latest age magmatic event in the Sao Luis cratonic fragment. Older zircon age of 2139 ± 10 Ma is interpreted as due to inheritance from the older granitoid or volcanic suites (magmatic sources?) or to contamination during emplacement. Lead isotope compositions indicate that the Pb incorporated in ore-related pyrite was probably sourced from regional, orogenic calc-alkaline granitoids of ca. 2160 Ma. Hydrothermal sericite from Caxias yielded a {sup 40}Ar/{sup 39}Ar plateau age of 1990 ± 30 Ma, which combined with the emplacement age of the Caxias Microtonalite brackets the age of gold mineralization between 2009 ± 11 and 1990 ± 30 Ma. (author)

  19. Ancient terrane boundaries as probable seismic hazards: A case study from the northern boundary of the Eastern Ghats Belt, India

    Directory of Open Access Journals (Sweden)

    Saibal Gupta

    2014-01-01

    Full Text Available In the eastern part of the Indian shield, late Paleozoic–Mesozoic sedimentary rocks of the Talchir Basin lie precisely along a contact of Neoproterozoic age between granulites of the Eastern Ghats Mobile Belt (EGMB and amphibolite facies rocks of the Rengali Province. At present, the northern part of the basin experiences periodic seismicity by reactivation of faults located both within the basin, and in the Rengali Province to the north. Detailed gravity data collected across the basin show that Bouguer anomalies decrease from the EGMB (∼+15 mGal, through the basin (∼−10 mGal, into the Rengali Province (∼−15 mGal. The data are consistent with the reportedly uncompensated nature of the EGMB, and indicate that the crust below the Rengali Province has a cratonic gravity signature. The contact between the two domains with distinct sub-surface structure, inferred from gravity data, coincides with the North Orissa Boundary Fault (NOBF that defines the northern boundary of the Talchir Basin. Post-Gondwana faults are also localized along the northern margin of the basin, and present-day seismic tremors also have epicenters close to the NOBF. This indicates that the NOBF was formed by reactivation of a Neoproterozoic terrane boundary, and continues to be susceptible to seismic activity even at the present-day.

  20. Fractal behavior in continental crustal heat production

    Science.gov (United States)

    Vedanti, N.; Srivastava, R. P.; Pandey, O. P.; Dimri, V. P.

    2011-02-01

    The distribution of crustal heat production, which is the most important component in the elucidation of continental thermal structure, still remains a theoretical assumption. In general the heat production values must decrease with depth, but the form of decrease of heat production in the crust is not well understood. The commonly used heat production models are: "block model", in which heat production is constant from the surface to a given depth and the "exponential model", in which heat production diminishes as an exponential function of depth. The exponential model is more widely used wherein sources of the errors are heterogeneity of rock and long wavelength changes due to changes in lithology and tectonic elements, and as such exponential distribution does not work satisfactorily for the entire crust. In the present study, we analyze for the first time, deep crustal heat production data of six global areas namely Dharwar craton (India), Kaapvaal craton (South Africa), Baltic shield (Kola, Russia), Hidaka metamorphic belt (Japan), Nissho pluton (Japan) and Continental Deep Drilling site (KTB, Germany). The power spectrum of all the studied data sets exhibits power law behaviour. This would mean slower decay of heat production with depth, which conforms to the known geologic composition of the crust. Minimum value of the scaling exponent has been found for the KTB borehole, which is apparently related to higher heat production of gneisses, however for other study areas, scaling exponent is almost similar. We also found that the lower values of scaling exponents are related to higher heat production in the crust as is the case in KTB. Present finding has a direct relevance in computation of temperature-depth profiles in continental regions.

  1. Evolving electrical SCLM models of the Australian continent - results of the South Australia AusLAMP deployment

    Science.gov (United States)

    Robertson, K. E.; Thiel, S.; Heinson, G. S.

    2017-12-01

    The Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) is an Australian initiative to map the Australian continental lithosphere using magnetotelluric (MT) stations to obtain a resistivity model of the subsurface. It is a joint project between Geoscience Australia, state surveys, and Universities. We present new MT 3D inversion results of the largest coherent array of the AusLAMP MT deployments to date covering two-thirds of South Australia, funded largely by the Geological Survey of South Australia with additional funding by Geoscience Australia and The University of Adelaide. The model extends across the South Australian Gawler Craton, including the Eucla Basin to the west of the craton and the Flinders Ranges and Curnamona Province to the east. The MT array covers parts of the Australian lithosphere, which has been largely unexplored with seismic tomography methods and provide a unique insight into the tectonic evolution of the continent. We incorporate 284 long-period (10s-10,000s) MT stations separated roughly every half degree latitude and longitude across an area spanning 1200 km x 800 km, south of latitude -28.5 degrees and from longitude 129 degrees to 141 degrees. We invert 24 discrete periods of the impedance tenor between 7 s and 13,000 s, and 22 different periods of the tipper data between 7s-8000 s period. The results show a heterogeneous lower crust and mantle lithosphere with a primarily resistive mantle (>1000 Ωm) lithosphere in the central and western part of the Gawler Craton and Eucla Domain. The model shows a generally NS oriented electric LAB offset from deeper cratonic lithosphere in the west to a shallow lithosphere along the eastern margin of the Gawler Craton extending further east towards the Proterozoic and Phanerozoic eastern part of Australia. The lower crust is generally resistive with elongated lower crustal conductivity anomalies, which are associated with major translithospheric shear zones likely existent

  2. Neoarchean history of the conjunction zone between the Belomorian mobile belt and the Karelian craton, Baltic shield: new isotopic data

    International Nuclear Information System (INIS)

    Alekseev, N.L.; Balaganskij, V.V.; Zinger, T.F.; Levchenkov, O.A.; Glebovitskij, V.A.; Makeev, A.F.; Yakovleva, S.Z.

    2004-01-01

    To study the neoarchean magmatism history of the conjunction zone between the Belomorian mobile belt and the Karelian craton one carried out U-Pb-isotope dating of volcanic zircons of the Kukas lake region. At the mentioned region one detected two pulses of the neoarchean volcanism that took place about 2877±45-2680.7±3.6 million years ago [ru

  3. NEW DATA ON AGE AND NATURE OF CARBONIZATION WITHIN SOUTHERN FLANK OF THE BAIKAL LEDGE OF THE SIBERIAN CRATON BASEMENT

    Directory of Open Access Journals (Sweden)

    Yu. V. Danilova

    2017-01-01

    Full Text Available The Baikal ledge rock formations in the Siberian craton structure are included in the Akitkan mobile belt which is considered as the Late Paleoproterozoic independent island arc system moved up to the ancient basement during the terrains amalgamation 1.91–2.00 Ga ago (Fig. 1 [Rosen, 2003; Gladkochub et al., 2009; Didenko et al., 2013].

  4. Seismic velocity structure of the crust and shallow mantle of the Central and Eastern United States by seismic surface wave imaging

    Science.gov (United States)

    Pollitz, Fred; Mooney, Walter D.

    2016-01-01

    Seismic surface waves from the Transportable Array of EarthScope's USArray are used to estimate phase velocity structure of 18 to 125 s Rayleigh waves, then inverted to obtain three-dimensional crust and upper mantle structure of the Central and Eastern United States (CEUS) down to ∼200 km. The obtained lithosphere structure confirms previously imaged CEUS features, e.g., the low seismic-velocity signature of the Cambrian Reelfoot Rift and the very low velocity at >150 km depth below an Eocene volcanic center in northwestern Virginia. New features include high-velocity mantle stretching from the Archean Superior Craton well into the Proterozoic terranes and deep low-velocity zones in central Texas (associated with the late Cretaceous Travis and Uvalde volcanic fields) and beneath the South Georgia Rift (which contains Jurassic basalts). Hot spot tracks may be associated with several imaged low-velocity zones, particularly those close to the former rifted Laurentia margin.

  5. Sulfur and lead isotope characteristics of the Pontes e Lacerda gold deposits, SW Amazonian Craton Brazil

    International Nuclear Information System (INIS)

    Geraldes, M.C.; Tassinari, C.C.G.; Babinski; M; Iyer, S

    2001-01-01

    This work deals with the characterization of the S and Pb isotope signatures in sulfides from the Pontes e Lacerda mesothermal gold deposits located in the SW sector of Amazonian craton. Stable and radiogenic isotopes have played an important role in the study of ore deposited and hydrothermal processes and they are most useful when can be used together. The purpose of this study is to constrain the sources and the mechanisms of gold deposition in Pontes e Lacerda region which may be a helpful contribution to an exploratory model in the area (au)

  6. Lateral heterogeneity and vertical stratification of cratonic lithospheric keels: examples from Europe, Siberia, and North America

    DEFF Research Database (Denmark)

    Artemieva, Irina; Cherepanova, Yulia; Herceg, Matija

    of the Precambrian lithosphere based on surface heat flow data, (ii) non-thermal part of upper mantle seismic velocity heterogeneity based on a joint analysis of thermal and seismic tomography data, and (iii) lithosphere density heterogeneity as constrained by free-board and satellite gravity data. The latter...... of the Gondwanaland does not presently exceed 250 km depth. An analysis of temperature-corrected seismic velocity structure indicates strong vertical and lateral heterogeneity of the cratonic lithospheric mantle, with a pronounced stratification in many Precambrian terranes; the latter is supported by xenolith data...

  7. Late Archaean mantle metasomatism below eastern Indian craton ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    crop NDD display mainly four distinct orientations viz., N-S, NNE-SSW, ...... also be trapped either along the grain boundary ... faster plate movements, high angle subduction would be ..... istry of oxide minerals in polymictic xenoliths from the.

  8. Reassessment of the geologic evolution of selected precambrian terranes in Brazil, based on SHRIMP U-Pb data, part 2: mineiro and Aracuai orogens and Southern Sao Francisco craton

    International Nuclear Information System (INIS)

    Silva, Luiz Carlos da; Pimentel, Marcio; Armstrong, Richard; Noce, Carlos Mauricio; Pedrosa-Soares, Antonio Carlos; Carneiro, Mauricio Antonio

    2002-01-01

    This paper discusses new zircon SHRIMP (Sensitive High Resolution Ion Microprobe) U-Pb geochronological data for 19 key-exposures of several geological units exposed at the eastern border of the Southern Sao Francisco Craton and at the adjacent Proterozoic Mineiro and Aracuai orogens. Samples were collected along several E-W tran sects, aiming at tracing the precise limit of the Sao Francisco Craton Archean basement, as well as assessing the extension of the successive proterozoic orogenic collages. Due to the complex geologic history and/or high grade metamorphism which most of the rock units investigated have undergone, zircon morphology and the U-Pb analytical data exhibit very complex patterns. These are characterized by a combination of inheritance, partial resetting and new zircon growth during high-grade metamorphism. As a consequence, very careful and detailed analyses of cathodoluminescence imagery were required to allow distinction between inheritance, newly melt-precipitated zircon and partially reset zircons, as well as between the ages of magmatic and metamorphic events. In the southeastern border of the craton 5 units yielded Archean crystallization ages ranging from ca. 3000-2700 Ma, with poorly constrained metamorphic ages ranging from ca. 2850 to 550 Ma. The TTG gneissic complex exposed to the east and south of the Quadrilatero Ferrifero, formerly ascribed to the Archean basement, have crystallization ages from ca. 2210 Ma to 2050 Ma, and can now be interpreted as representing pre- to syn-collisional magmatic phases of the Mineiro Belt. Metamorphic ages of ca. 2100 Ma and 560 Ma are also well constrained in zircon populations from these gneisses. The crystallization age of ca 1740 Ma observed for an alkaline granite of the Borrachudos Suite (intrusive into the Archean basement east of the Southern Espinhaco Range) confirmed previous conventional U-Pb data for this Paleoproterozoic rift-related magmatism. One of the major basement inliers within the

  9. Crustal structure and rift tectonics across the Cauvery–Palar basin ...

    Indian Academy of Sciences (India)

    The Cauvery–Palar basin is a major peri-cratonic rift basin located along the Eastern Continental. Margin of India ..... density P(k) of a magnetized body having infinite extensions in the .... aly data must be brought down to the sea level through ...

  10. Petrology, geochemistry and zirconology of impure calcite marbles from the Precambrian metamorphic basement at the southeastern margin of the North China Craton

    Science.gov (United States)

    Liu, Yi-Can; Zhang, Pin-Gang; Wang, Cheng-Cheng; Groppo, Chiara; Rolfo, Franco; Yang, Yang; Li, Yuan; Deng, Liang-Peng; Song, Biao

    2017-10-01

    Impure calcite marbles from the Precambrian metamorphic basement of the Wuhe Complex, southeastern margin of the North China Craton, provide an exceptional opportunity to understand the depositional processes during the Late Archean and the subsequent Palaeoproterozoic metamorphic evolution of one of the oldest cratons in the world. The studied marbles are characterized by the assemblage calcite + clinopyroxene + plagioclase + K-feldspar + quartz + rutile ± biotite ± white mica. Based on petrography and geochemistry, the marbles can be broadly divided into two main types. The first type (type 1) is rich in REE with a negative Eu anomaly, whereas the second type (type 2) is relatively poor in REE with a positive Eu anomaly. Notably, all marbles exhibit remarkably uniform REE patterns with moderate LREE/HREE fractionation, suggesting a close genetic relationship. Cathodoluminescence imaging, trace elements and mineral inclusions reveal that most zircons from two dated samples display distinct core-rim structures. Zircon cores show typical igneous features with oscillatory growth zoning and high Th/U ratios (mostly in the range 0.3-0.7) and give ages of 2.53 - 2.48 Ga, thus dating the maximum age of deposition of the protolith. Zircon rims overgrew during granulite-facies metamorphism, as evidenced by calcite + clinopyroxene + rutile + plagioclase + quartz inclusions, by Ti-in-zircon temperatures in the range 660-743 °C and by the low Th/U (mostly marbles are ascribed to syn-depositional felsic hydrothermal activity which occurred at 2.53 - 2.48 Ga. Our results, together with other published data and the inferred tectonic setting, suggest that the marbles' protolith is an impure limestone, rich in detrital silicates of igneous origin, deposited in a back-arc basin within an active continental margin during the late Archean and affected by synchronous high-T hydrothermalism at the southeastern margin of the North China Craton.

  11. Present mantle flow in North China Craton constrained by seismic anisotropy and numerical modelling

    Science.gov (United States)

    Qu, W.; Guo, Z.; Zhang, H.; Chen, Y. J.

    2017-12-01

    North China Carton (NCC) has undergone complicated geodynamic processes during the Cenozoic, including the westward subduction of the Pacific plate to its east and the collision of the India-Eurasia plates to its southwest. Shear wave splitting measurements in NCC reveal distinct seismic anisotropy patterns at different tectonic blocks, that is, the predominantly NW-SE trending alignment of fast directions in the western NCC and eastern NCC, weak anisotropy within the Ordos block, and N-S fast polarization beneath the Trans-North China Orogen (TNCO). To better understand the origin of seismic anisotropy from SKS splitting in NCC, we obtain a high-resolution dynamic model that absorbs multi-geophysical observations and state-of-the-art numerical methods. We calculate the mantle flow using a most updated version of software ASPECT (Kronbichler et al., 2012) with high-resolution temperature and density structures from a recent 3-D thermal-chemical model by Guo et al. (2016). The thermal-chemical model is obtained by multi-observable probabilistic inversion using high-quality surface wave measurements, potential fields, topography, and surface heat flow (Guo et al., 2016). The viscosity is then estimated by combining the dislocation creep, diffusion creep, and plasticity, which is depended on temperature, pressure, and chemical composition. Then we calculate the seismic anisotropy from the shear deformation of mantle flow by DREX, and predict the fast direction and delay time of SKS splitting. We find that when complex boundary conditions are applied, including the far field effects of the deep subduction of Pacific plate and eastward escaping of Tibetan Plateau, our model can successfully predict the observed shear wave splitting patterns. Our model indicates that seismic anisotropy revealed by SKS is primarily resulting from the LPO of olivine due to the shear deformation from asthenospheric flow. We suggest that two branches of mantle flow may contribute to the

  12. Paleointensity determination on Neoarchaean dikes within the Vodlozerskii terrane of the Karelian craton

    Science.gov (United States)

    Shcherbakova, V. V.; Lubnina, N. V.; Shcherbakov, V. P.; Zhidkov, G. V.; Tsel'movich, V. A.

    2017-09-01

    The results of paleomagnetic studies and paleointensity determinations from two Neoarchaean Shala dikes with an age of 2504 Ma, located within the Vodlozerskii terrane of the Karelian craton, are presented. The characteristic components of primary magnetization with shallow inclinations I = -5.7 and 1.9 are revealed; the reliability of the determinations is supported by two contact tests. High paleointensity values are obtained by the Thellier-Coe and Wilson techniques. The calculated values of the virtual dipole moment (11.5 and 13.8) × 1022 A m2 are noticeably higher than the present value of 7.8 × 1022 A m2. Our results, in combination with the previous data presented in the world database, support the hypothesized existence of a period of high paleointensity in the Late Archaean-Early Proterozoic.

  13. Middle Eastern rhinoplasty.

    Science.gov (United States)

    Azizzadeh, Babak; Mashkevich, Grigoriy

    2010-02-01

    The ethnic appearance of the Middle Eastern nose is defined by several unique visual features, particularly a high radix, wide overprojecting dorsum, and an amorphous hanging nasal tip. These external characteristics reflect distinct structural properties of the osseo-cartilaginous nasal framework and skin-soft tissue envelope in patients of Middle Eastern extraction. The goal, and the ultimate challenge, of rhinoplasty on Middle Eastern patients is to achieve balanced aesthetic refinement, while avoiding surgical westernization. Detailed understanding of the ethnic visual harmony in a Middle Eastern nose greatly assists in preserving native nasal-facial relationships during rhinoplasty on Middle Eastern patients. Esthetic alteration of a Middle Eastern nose follows a different set of goals and principles compared with rhinoplasties on white or other ethnic patients. This article highlights the inherent nasal features of the Middle Eastern nose and reviews pertinent concepts of rhinoplasty on Middle Eastern patients. Essential considerations in the process spanning the consultation and surgery are reviewed. Reliable operative techniques that achieve a successful aesthetic outcome are discussed in detail. Copyright 2010 Elsevier Inc. All rights reserved.

  14. Emplacement and deformation of the A-type Madeira granite (Amazonian Craton, Brazil)

    Science.gov (United States)

    Siachoque, Astrid; Salazar, Carlos Alejandro; Trindade, Ricardo

    2017-04-01

    The Madeira granite is one of the Paleoproterozoic (1.82 Ga) A-type granite intrusions in the Amazonian Craton. It is elongated in the NE-SW direction and is composed of four facies. Classical structural techniques and the anisotropy of magnetic susceptibility (AMS) method were applied to the study of its internal fabric. Magnetic susceptibility measurements, thermomagnetic curves, remanent coercivity spectra, optical microscopy and SEM (scanning electron microscopy) analyses were carried out on the earlier and later facies of the Madeira granite: the rapakivi granite (RG) and the albite granite (AG) respectively. The last one is subdivided into the border albite granite (BAG) and the core albite granite (CAG) subfacies. AMS fabric pattern is controlled by pure magnetite in all facies, despite significant amounts of hematite in the BAG subfacies. Microstructural observations show that in almost all sites, magnetic fabric correlates to magmatic state fabrics that are defined by a weak NE-SW orientation of mafic and felsic silicates. However, strain mechanisms in both subfacies of AG also exhibit evidence for solid-state deformation at high to moderate temperatures. Pegmatite dyke, strike slip fault (SFA-B-C), hydrothermal vein, normal fault (F1-2) and joint (J) structures were observed and their orientation and kinematics is consistent with the magmatic and solid-state structures. Dykes, SFA-C and F1, are usually orientated along the N70°E/40°N plane, which is nearly parallel to the strike of AMS and magmatic foliations. In contrast, veins, SFB, F2 and some J are oriented perpendicular to the N70°E trend. Kinematic analysis in these structures shows evidence for a dextral sense of movement in the system in the brittle regime. The coherent structural pattern for the three facies of Madeira granite suggests that the different facies form a nested pluton. The coherence in orientation and kinematics from magmatic to high-temperature solid-state, and into the brittle

  15. The Dom Feliciano belt (Brazil-Uruguay)and its fore land (Rio de la Plata Craton): framework, tectonic evolution and correlations with similar terranes of southwestern Africa

    International Nuclear Information System (INIS)

    Basei, M.; Siga, O.; Masquelin, H.; Harara, O.; Reis Neto, J.; Preciozzi, F.

    2000-01-01

    The Dom Feliciano Belt (DFB) stretches for ca. 1,200 km along southeastern Brazil and eastern Uruguay, with an average width of 150 km. From its northern limit in Santa Catarina to its termination m Uruguay, DFB is internally organized according three crustal segments characterized, from southeast to northwest, by a Granitoid belt (calci-alkaline to alkaline granitoid rocks deformed to different degrees); a Schist belt (volcano-sedimentary rocks metamorphosed from green schist to amphibolite facies), and a Fore land belt (sedimentary and anchimetamorphic volcanic rocks), the latter situated between the Schist belt and the old western terranes. Despite discontinuously covered by younger sediments, the continuity of these three segments is suggested by the similar lithotypes and structural characteristics, as well as by the gravimetric geophysical signature.In this work, DBF is interpreted as the product of successive subduction s and collisions related to the agglutination of different terranes generated or intensely reworked from the Neoproterozoic to the Cambrian, during the Brasiliano and Rio Doce orogenesis, with maximum time starting at 900 Ma (opening of the Adamastor Ocean) and ending at 530 Ma (deformation of the fore land basins) related to the tecto no-magmatic events associated with the formation of the Western Gondwana.Besides the Neoproterozoic DFB and its fore land, the Rio de la Plata Craton and the Luis Alves Microplate, constituted by Paleoproterozoic gneissic-migmatitic rocks, two other tectonic units can be recognized in southeastern Brazil and eastern Uruguay: the Sao Gabriel Block (RS) where Neoproterozoic juvenile material can be characterized in regional scale (in great part associated with an island are), and the Punta del Este Terrane, which presents, in southern Uruguay, an ortho gneiss basement with ages around 1,000 Ma and a meta sedimentary cover (Rocha Group), which can correspond in the South-American portion, to the Namaqua and Gariep

  16. Carbon, nitrogen, and sulfur geochemistry of Archean and Proterozoic shales from the Kaapvaal Craton, South Africa

    Science.gov (United States)

    Watanabe, Yumiko; Naraoka, Hiroshi; Wronkiewicz, David J.; Condie, Kent C.; Ohmoto, Hiroshi

    1997-08-01

    The C, N, and S contents and VC and δ 13Cδ 34S values were analyzed for 100 shale samples from ten formations, 3.0 to 2.1 Ga in age, in the central and eastern regions of the Kaapvaal Craton, South Africa. The Kaapvaal shales are characterized by generally low contents of organic C (range 0.06-2.79 wt%, average 0.47 wt%), N (range facies). From the theoretical relationships between the H/C ratios of kerogen and organic C contents of shales, the original C contents of the Archean and Proterozoic shales from the Kaapvaal Craton are estimated to be on average ˜2 wt%. These values are similar to the average organic C content of modern marine sediments. This suggests that the primary organic productivity and the preservation of organic matter in the ocean during the period of 3.0 to 2.1 Ga were similar to those in the Phanerozoic era, provided the flux of clastic sediments to the ocean was similar. This would also imply that the rate of O 2 accumulation in the atmosphere-ocean system, which has equaled the burial rate of organic matter in sediments, has been the same since ˜3.0 Ga. The δ 34S values of bulk-rock sulfides (mostly pyrite) range from +2.7 to +7.4%‰ for seven sulfide-rich samples of ˜2.9 Ga to ˜2.6 Ga. These values are consistent with a suggestion by Ohmoto (1992) and Ohmoto et al. (1993) that most pyrite crystals in Archean shales were formed by bacterial reduction of seawater sulfate with δ 34S values between +2 and +10‰, and that the Archean seawater was sulfate rich. Changes in the δ 13C org values during maturation of kerogen were evaluated with theoretical calculations from the experimental data of Peters et al. (1981) and Lewan (1983), and from the observations by Simoneit et al. (1981) on natural samples. These evaluations suggest that the magnitudes of δ 13C org increase are much less than those estimated by Hayes et al. (1983) and Des Marais et al. (1992), and only about 2 to 3%‰ for the kerogens that decreased their H/C ratios from

  17. Audio-magnetotelluric investigation of sulfide mineralization in Proterozoic-Archean greenstone belts of Eastern Indian Craton

    Science.gov (United States)

    Singh, Shailendra; Maurya, Ved P.; Singh, Roshan K.; Srivastava, Shalivahan; Tripathi, Anurag; Adhikari, P. K.

    2018-04-01

    Greenstone belts are well known for gold occurrences at different regions of the world. The Dhanjori basin in the eastern Singhbhum region shows major characteristics of a rifted greenstone belt. Initially, we conducted 14 audio-magnetotelluric (AMT) measurements for a profile of ˜ 20 km in the frequency range of 1 kHz to 10 Hz over this rather complex geologic environment covering Dhanjori Volcanics (DhV) and Kolhan Group (KG). Subsequently, gravity and magnetic surveys were also conducted over this AMT profile. The purpose of the survey was to identify and map conductive features and to relate them to metallogeny of the area along with the mapping of the basement of Dhanjori basin. The strike analysis showed N30°W strike for DhV for all the frequencies and for sites over KG domain in the frequency range of 100-10 Hz, but for KG domain, the obtained strike in 1 kHz to 100 Hz is N45°E. As the combination of transverse electric (TE), transverse magnetic (TM) and tipper (Tzy) can recover the electrical signature in complex geological environment, we discuss the conductivity model obtained from TE+TM+Tzy only. The inversion was carried for the regional profile with 14 sites and for 7 sites over KG domain. Conductivity model shows two well resolved conductors, one each in KG and Quartz Pebble Conglomerate Dhanjori (QPCD) domains respectively showing common linked concordant features between these regional and KG profiles. The conductors are interpreted as sulfide mineralization linked with QPCD group of rocks which may host gold. These conductors are also horizontally disposed due to the intrusive younger Mayurbhanj Granite. These intrusives correlate well with the gravity modeling as well. The thickness of the Dhanjori basin at the central is about 3.0 km, similar to that from gravity modeling. The conductivity model also indicates the presence of shallow conductors, but could not be resolved due to lack of high frequency data. However, the results from the close

  18. Fractal behavior in continental crustal heat production

    Directory of Open Access Journals (Sweden)

    N. Vedanti

    2011-02-01

    Full Text Available The distribution of crustal heat production, which is the most important component in the elucidation of continental thermal structure, still remains a theoretical assumption. In general the heat production values must decrease with depth, but the form of decrease of heat production in the crust is not well understood. The commonly used heat production models are: "block model", in which heat production is constant from the surface to a given depth and the "exponential model", in which heat production diminishes as an exponential function of depth. The exponential model is more widely used wherein sources of the errors are heterogeneity of rock and long wavelength changes due to changes in lithology and tectonic elements, and as such exponential distribution does not work satisfactorily for the entire crust. In the present study, we analyze for the first time, deep crustal heat production data of six global areas namely Dharwar craton (India, Kaapvaal craton (South Africa, Baltic shield (Kola, Russia, Hidaka metamorphic belt (Japan, Nissho pluton (Japan and Continental Deep Drilling site (KTB, Germany. The power spectrum of all the studied data sets exhibits power law behaviour. This would mean slower decay of heat production with depth, which conforms to the known geologic composition of the crust. Minimum value of the scaling exponent has been found for the KTB borehole, which is apparently related to higher heat production of gneisses, however for other study areas, scaling exponent is almost similar. We also found that the lower values of scaling exponents are related to higher heat production in the crust as is the case in KTB. Present finding has a direct relevance in computation of temperature-depth profiles in continental regions.

  19. STAGE MODEL FOR GONDWANA ASSEMBLY

    African Journals Online (AJOL)

    the Eastern Granulites, the Kitumbi rocks occur as small enclaves ... out of collision of India, Madagascar, parts of Easten Antarctica and the Kalahari craton (IMSLEK ... Hepworth (1972) describes other granulite occurrences in the western and central parts of ..... of Gondwana. In: A. Kroner (ed) Precambrian Plate Tectonics,.

  20. U-Pb geochronology of Martín García, Sola, and Dos Hermanas Islands (Argentina and Uruguay): Unveiling Rhyacian, Statherian, Ectasian, and Stenian of a forgotten area of the Río de la Plata Craton

    Science.gov (United States)

    Santos, João O. S.; Chernicoff, Carlos J.; Zappettini, Eduardo O.; McNaughton, Neal J.; Greau, Y.

    2017-12-01

    The Río de la Plata Craton is one of the three major cratons of South America. The craton is largely covered by sedimentary basins where its most exposed area is Buenos Aires-Piedra Alta Province (Chernicoff et al., 2014). This province includes the Martín García Island in the confluence of Uruguay River and the Río de la Plata estuary. Despite to be a reference area for the craton the Martín García Island lacks modern geological investigation. We present U-Pb SIMS (secondary ion mass spectrometer) geochronological data on zircon and titanite, as well as Hf isotope determinations on zircon, from rocks of Martín García Island (Argentina), Sola and Dos Hermanas Islands (Uruguay) and from Paso Severino Formation (Uruguay). We investigated: 1) Rhyacian intermediate-to acidic plutonic, arc-type rocks of the Florida Belt dated between 2090 Ma and 2115 Ma, derived from juvenile Neoarchean crust (TDMHf: 2.52 Ga; average εHf: +3.62); 2) Rhyacian metadacite (San José metamorphic belt) of 2127 Ma; 3) Statherian metagabbros of 1724-1734 Ma, with Transplatense inheritance; 4) Early Ectasian metagabbro of 1392 Ma, with Rhyacian inheritance; and 5) Stenian metagabbros of 1193 Ma (TDMHf: 2.00 Ga, εHf: 0.1). Most of the dated orthogneisses show Brasilian-age (from 778 to 550 Ma) Pb loss in the zircons, interpreted to be caused by shearing or uplifting during Neoproterozoic. The results show that the area is not exclusively Rhyacian in age but encompasses Statherian, Ectasian, and Stenian gabbros. The last two are interpreted as distal intrusions associated to the Sunsás Orogen. All post-Transplatense metagabbros have geochemical signature of island arc basalt derived from primitive mantle with enrichment of LILE and depletion of HFSE. These characteristics point to the recurrence of magma chambers intermittently active during the Rhyacian, Statherian, Ectasian, and Stenian, all with a similar source. The term "Transplatense" is used to replace "Trans-Amazonian" events

  1. Sedimentology and stratigraphy of Neoproterozoic-lower Paleozoic carbonate-siliciclastic succession of the southwesternmost Amazon Craton, state of Rondônia, Brazil

    OpenAIRE

    Afonso, Jhon Willy Lopes; Nogueira, Afonso César Rodrigues

    2018-01-01

    ABSTRACT: Facies and stratigraphic analysis were carried out in Neoproterozoic-Lower Paleozoic carbonate-siliciclastic deposits of Cacoal and Pimenta Bueno formations exposed on basement rocks and into the Pimenta Bueno Graben, northwestern portion of Parecis Basin, southwesternmost Amazon Craton. The redescription and redefinion of this succession confirmed the previous interpretation for the Cacoal Formation as a Marinoan (~ 635 Ma) cap carbonate. The Cacoal Formation is subdivided here in ...

  2. Combined teleseismic imaging of the structure of southern African cratons using P-receiver functions and P-and S-finite-frequency tomography

    DEFF Research Database (Denmark)

    Soliman, Mohammad Youssof Ahmad; Thybo, Hans; Levander, Alan

    2011-01-01

    bands (1, 0.5 and 0.25 Hz for P and 0.1, 0.05 and 0.02 Hz for S) to obtain 3-D P- and S-wave perturbation models for the upper mantle. Crustal corrections are based on the RF models. Tests showed that our dataset is able to resolve structure of 3°x3° up to 400 km depth. The high-velocity cratonic roots...

  3. Deep physical structure and geotectonic implications of the eastern margin of the Qinghai–Tibet Plateau

    Directory of Open Access Journals (Sweden)

    Jun Li

    2016-10-01

    Full Text Available The eastern margin of the Qinghai–Tibet Plateau (QTP is the focus of studies on eastward lateral extrusion of the latter’s crustal material. This study aims to explore the structural response of the QTP’s eastern crust–mantle to the extrusion, and the basis for the latter’s geological structure. Data on long-period magnetotelluric sounding of cross-tectonic units and Bouguer gravity were used to determine the physical structure of the crust–mantle at the plateau’s eastern margin. The findings are as follows: (i the apparent density structure indicates extensive presence of a low-density material in the middle–lower crusts of the Songpan and Sichuan–Yunnan blocks at the QTP’s eastern margin. On the other hand, the Yangtze cratonic block (Sichuan Basin contains a material with a significantly higher density. To the west of the Longmenshan–Panxi tectonic zones, and along the lower crust at 40–50 km depth, is an obvious low-density zone aligned in a northeast–southwest orientation; (ii the electrical structural model spanning Songpan block–Longmenshan tectonic zone–Yangtze block reveals three distinct electrical structural units along the cross-section bounded by the Longmenshan tectonic zone. The first is the Songpan block, which has high and low resistivity at the shallow layer and middle–lower crusts, respectively. Next is the Yangtze craton, which has low and relatively higher resistivity at the shallow layer and middle–lower crusts, respectively. Third is the Longmenshan transitional tectonic zone, whose shallow layer and deep structure are characterized by an electrical structure with a thrust nappe towards the east, and a high-conductivity material extending to the lithospheric mantle, respectively; (iii the apparent density and electrical structures indicate that the Panxi tectonic zone has a weakened structure in the lower crust; and (iv physical properties of the QTP’s deep structure indicate that its

  4. Architecture and mineral deposit settings of the Altaid orogenic collage: a revised model

    Science.gov (United States)

    Yakubchuk, Alexander

    2004-09-01

    The Altaids are an orogenic collage of Neoproterozoic-Paleozoic rocks located in the center of Eurasia. This collage consists of only three oroclinally bent Neoproterozoic-Early Paleozoic magmatic arcs (Kipchak, Tuva-Mongol, and Mugodzhar-Rudny Altai), separated by sutures of their former backarc basins, which were stitched by new generations of overlapping magmatic arcs. In addition, the Altaids host accreted fragments of the Neoproterozoic to Early Paleozoic oceanic island chains and Neoproterozoic to Cenozoic plume-related magmatic rocks superimposed on the accreted fragments. All these assemblages host important, many world-class, Late Proterozoic to Early Mesozoic gold, copper-molybdenum, lead-zinc, nickel and other deposits of various types. In the Late Proterozoic, during breakup of the supercontinent Rodinia, the Kipchak and Tuva-Mongol magmatic arcs were rifted off Eastern Europe-Siberia and Laurentia to produce oceanic backarc basins. In the Late Ordovician, the Siberian craton began its clockwise rotation with respect to Eastern Europe and this coincides with the beginning of formation of the Mugodzhar-Rudny Altai arc behind the Kipchak arc. These earlier arcs produced mostly Cu-Pb-Zn VMS deposits, although some important intrusion-related orogenic Au deposits formed during arc-arc collision events in the Middle Cambrian and Late Ordovician. The clockwise rotation of Siberia continued through the Paleozoic until the Early Permian producing several episodes of oroclinal bending, strike-slip duplication and reorganization of the magmatic arcs to produce the overlapping Kazakh-Mongol and Zharma-Saur-Valerianov-Beltau-Kurama arcs that welded the extinct Kipchak and Tuva-Mongol arcs. This resulted in amalgamation of the western portion of the Altaid orogenic collage in the Late Paleozoic. Its eastern portion amalgamated only in the early Mesozoic and was overlapped by the Transbaikal magmatic arc, which developed in response to subduction of the oceanic crust

  5. Lamprophyres from the Harohalli dyke swarm in the Halaguru and Mysore areas, Southern India: Implications for backarc basin magmatism

    Science.gov (United States)

    Lanjewar, Shubhangi; Randive, Kirtikumar

    2018-05-01

    The Bangalore and Harohalli dyke swarms occur in the eastern part of the Dharwar craton. The older Bangalore dyke swarm is made up of dolerites, trending east-west, and the younger contains alkaline dykes that trend approximately north-south. The lamprophyres of the Harohalli dyke swarm occur in the Halaguru and Mysore industrial areas where they are exposed as fresh porphyritic - panidiomorphic dykes, containing crustal xenoliths, and showing chilled contacts with the country rock charnokites. They are chiefly composed of amphiboles which form well-developed phenocrysts. Clinopyroxenes are present in some of the dykes. Compositional zoning is observed in clinopyroxenes and amphiboles; their zoning patterns indicate that the magma experienced cryptic variations and that fractional crystallization was a dominant process in the evolution of the Harohalli Lamprophyres (HRL). The HRL are calc-alkaline with shoshonitic affinity and exhibit a K2O/Na2O ratio of ∼1. They show primitive (MORB-like) trace-element characters. LILE and LREE both show marginally enriched patterns; whereas HFSE and HREE show strongly depleted patterns. In the regional geologic sense, HRL dykes are characterised by two major influences; namely, (i) primary source region characteristics, which are geochemically more primitive, roughly falling within fields of primitive - MORB and enriched- MORB and (ii) the continental lithosphere. The data points for the HRL distinctly show their proximity to N-MORB and scatter towards the continental crust. Moreover, features like xenolith assimilation might influence the trace-element characteristics of the HRL dykes. Such magmas with mixed characters can be formed in a backarc basin environment. Geochemical proxies such as Ba/Nb vs Nb/Yb, Ba/Th vs Th/Nb, and the water content of magmas; which have been effectively used for discriminating backarc basin magmas worldwide, also indicate that the HRL magmas were generated in a backarc environment with inputs from

  6. Metallogenesis of Precambrian gold deposits in the Wutai greenstone belt: Constrains on the tectonic evolution of the North China Craton

    Directory of Open Access Journals (Sweden)

    Ju-Quan Zhang

    2018-03-01

    Full Text Available The Wutai greenstone belt in central North China Craton (NCC hosts a number of Precambrian gold deposits and ore occurrences. Based on the host rock association, these can be divided into Banded Iron Formation (BIF, meta-volcano-sedimentary and meta-conglomerate types. The two former types formed during ∼2.5–2.3 Ga and the third one at ∼1.85 Ga. The characteristics of these Precambrian gold deposits are broadly similar with those of the orogenic gold deposits. Based on available geochronological data, here we reconstruct the major tectonic events and their relationship with gold mineralization in the Wutai-Hengshan-Fuping region during Neoarchean to Paleoproterozoic as follows. (1 ∼2.6–2.5 Ga: widespread intrusion of tonalite-trondhjemite-granodiorite (TTG magmas in the Hengshan terrane and Fuping continental arc, formation of the Wutai volcanic arc in the southern margin of Hengshan terrane with granitoids emplacement, and the Hengshan-Wutai intra-oceanic arc accretion to the Fuping arc at the end of Neoarchean. (2 ∼2.5–2.3 Ga: the subduction of Hengshan arc from north leading to persistent magmatism and orogenic gold mineralization. (3 ∼2.2–2.1 Ga: extension leading to the formation of graben structure in the Wutai and Fuping region, deposition of the Hutuo and Wanzi Group sediments, formation of placer gold through erosion of the orogenic gold deposits. (4 ∼2.2–2.0 Ga: widespread magmatism in the Wutai-Hengshan-Fuping region. (5 ∼1.95–1.8 Ga: regional metamorphism associated with collision of the Western and Eastern Blocks of the NCC and associated orogenic gold deposits. The multiple subduction-accretion-collision history and subsequent deep erosion has significantly affected most of the Precambrian gold deposits in the Wutai greenstone belt.

  7. U-Pb geochronology and paleomagnetism of the Neoproterozoic St Simeon dolerite dykes, Quebec: an eastern Laurentian perspective of Ediacaran Rodinia breakup

    Science.gov (United States)

    Pisarevsky, Sergei; Murphy, Brendan; Hamilton, Mike; Söderlund, Ulf; Hodych, Joseph

    2013-04-01

    The St Simeon (SS) mafic dykes (150 km NE of Quebec City) are now dated at 548 ± 1 Ma (U-Pb; baddeleyite). This age is similar to a published LA-ICPMS zircon age of 550 ± 7 Ma for the Mt. St-Anselme (MS) basalts, which supports previous inferences of (i) a genetic relationship between them, (ii) the pene-contemporaneity of OIB-type mafic magmatism in East Laurentia and (iii) the existence of two late Ediacaran plumes that attended the final breakup of Rodinia and opening of the Iapetus Ocean and Tornquist Sea. Both the SS dykes and the MS basalts were sampled for paleomagnetic study. The paleomagnetic pole for SS is similar to the previously published pole for coeval basalts (Skinner Cove, SC) from Newfoundland. Unlike SC, the St Simeon pole represents rocks which are unambiguously coherent tectonically with the Laurentian Craton. This new pole is also coeval with high quality poles from the Winter Coast (Baltica) and provides paleomagnetic constraints on the history of the final breakup of Rodinia and opening of Eastern Iapetus and Tornquist Sea.

  8. Magnetic studies and U Pb geochronology of the Uruguayan dyke swarm, Rio de la Plata craton, Uruguay: paleomagnetic and economic implications

    Science.gov (United States)

    Halls, Henry C.; Campal, Nestor; Davis, Don W.; Bossi, Jorge

    2001-09-01

    A U-Pb age on baddeleyite of 1790±5 Ma has been obtained from a single dyke of the Uruguayan tholeiitic dyke swarm from the Rio de la Plata craton. Palaeomagnetic results from this and 10 other dykes yield two components, one (A) has the following paleomagnetic parameters: declination=12°, inclination=-16°, α95=7°, latitude of paleopole=61°, longitude=-31°, dp=4°, dm=7°, paleolatitude=-8°, whereas another (B), about 20° steeper, has a direction closer to the present Earth's field direction in Uruguay. Neither magnetisation is considered primary, although the A component may represent a composite between B and a primary component. A field test for the primary nature of the remanences was inconclusive, and no primary pole positions of similar age from other South American cratons are available for comparison. The magnetic results demonstrate that darker-coloured andesite dykes that are sought for facing and monument stone (as 'black granite') can be easily differentiated from more andesi-basaltic, lighter coloured, less valuable dykes of the same swarm, using aeromagnetic data. The results suggest that a high resolution airborne magnetic survey could constitute an important exploration tool for the Uruguayan 'black granite' industry.

  9. Sedimentology and stratigraphy of Neoproterozoic-lower Paleozoic carbonate-siliciclastic succession of the southwesternmost Amazon Craton, state of Rondônia, Brazil

    Directory of Open Access Journals (Sweden)

    Jhon Willy Lopes Afonso

    2018-02-01

    Full Text Available ABSTRACT: Facies and stratigraphic analysis were carried out in Neoproterozoic-Lower Paleozoic carbonate-siliciclastic deposits of Cacoal and Pimenta Bueno formations exposed on basement rocks and into the Pimenta Bueno Graben, northwestern portion of Parecis Basin, southwesternmost Amazon Craton. The redescription and redefinion of this succession confirmed the previous interpretation for the Cacoal Formation as a Marinoan (~ 635 Ma cap carbonate. The Cacoal Formation is subdivided here in two units separate by sharp contact found exclusively overlying Mesoproterozoic crystalline basement rocks: 1 a homonymous formation characterized by diamictites, sandstones and siltstones with dropstones interpreted as glacio-marine deposits; and 2 the Espigão d’Oeste Formation that consists of dolostone, dolomitic stromatolites, dolostone-siltstone rhythmite and siltstone interpreted as shallow to moderately deep platform deposits. The Ordovician to Silurian Pimenta Bueno Formation is a filling of Pimenta Bueno graben and overlies locally the Meso and Neoproterozoic rocks. This unit consists in diamictites, sandstones, siltstones and pelites interpreted as glacial-marine and tide- to storm-influenced platform deposits, recording a glacio-eustatic regressive-transgressive event. This new stratigraphic proposal modify the current stratigraphy for the Parecis Basin and suggest, at least, two levels of glaciation exposed in the sothwesternmost Amazon Craton related to the Marinoan and Late Ordovician-Early Silurian events.

  10. Did clockwise rotation of Antarctica cause the break-up of Gondwanaland? An investigation in the 'deep-keeled cratons' frame for global dynamics

    Science.gov (United States)

    Osmaston, M. F.

    2012-04-01

    Introduction. The 'deep-keeled cratons' frame for global dynamics is the result of seeking Earth-behaviour answers to the following outside-the-box proposition:- "If cratons have tectospheric keels that reach or approach the 660 km discontinuity, AND the 660 level is an effective barrier to mantle circulation, then obviously (i) when two cratons separate, the upper mantle to put under the nascent ocean must arrive by a circuitous route and, conversely, (ii) if they approach one another, the mantle volume that was in between them must get extruded sideways." Surprisingly it has turned out [1 - 4] that Earth dynamical behaviour for at least the past 150 Ma provides persuasive affirmation of both these expectations and that there is a rational petrological explanation for the otherwise-unexpected immobility of subcratonic material to such depths [5 - 7]. Clockwise rotation of Antarctica? This contribution greatly amplifies my original plate dynamical arguments for suggesting [8] that such rotation is ongoing. Convection is unsuited to causing rotation about a pole within the plate so, as noted then, a gearwheel-like linkage to Africa at the SWIR would provide its clearly CCW (Biscay-Caucasus) relationship to the Mediterranean belt for the past 100 Ma, also seen in its separation from South America. Gearwheel-like linkage of motion requires the presence of some kind of E-W restraint further north. In that case it was the N Africa/Arabia involvement in the Alpide belt, but the earlier opening of the central Atlantic by the eastward motion of Africa, suggests its rigid Gondwanan attachment to Antarctica rotation at that time, with little constraint in the north. Further east, the seafloor data show that Australia-Antarctica separation involved no such opposite rotational linkage, so, with no E-W mechanical constraint in the north by Indonesia, they must have rotated together, as is recorded by Australia's eastward motion to generate the Mesozoic seafloor at its western

  11. Lithospheric diamond formation as a consequence of methane-rich volatile flooding: An example from diamondiferous eclogite xenoliths of the Karelian craton (Finland)

    Science.gov (United States)

    Smart, K. A.; Cartigny, P.; Tappe, S.; O'Brien, H.; Klemme, S.

    2017-06-01

    A collection of 61 xenocrystic and 12 eclogite xenolith-derived diamonds from the 600 Ma Lahtojoki kimberlite in central Finland has been investigated. Calculated pressure and temperature conditions for the diamondiferous eclogites are in excess of 5.5 GPa and 1300 °C, suggesting residence depths greater than 180 km, near the base of the Karelian cratonic mantle lithosphere. Geochemically, the eclogite xenoliths have gabbroic compositions showing positive Eu and Sr anomalies, relatively low ΣREE and elevated Al2O3 contents, yet garnets have ambiguous δ18O values of 5.7‰ and 5.9‰. Gabbroic eclogite formation could therefore be linked to either subduction processes during the 1.9 Ga Svecofennian orogeny or to cumulate processes during 2.1 Ga rift-induced magmatism. Determination of the oxygen fugacity of Lahtojoki eclogite xenoliths from both this work and previous studies suggests that diamond-bearing eclogites may be more reduced (ΔFMQ-3.5) compared to barren eclogites (ΔFMQ-1.7). While recycled oceanic crust protoliths for the eclogites remain a possibility, the carbon isotopic compositions and nitrogen abundances of the Lahtojoki diamonds indicate mantle-derived volatile sources. All diamonds (i.e., loose and eclogite xenolith-derived) display a restricted range of δ13C values from -7.8‰ to -3.7‰ that overlaps with the carbon isotopic composition of Earth's mantle. The Lahtojoki diamond δ13C values form a negatively skewed distribution, indicating diamond growth from reduced mantle-derived carbon sources such as methane- (CH4) bearing fluids. Nitrogen contents of the Lahtojoki diamonds range from 40 to 1830 atomic ppm with a mean of ∼670 atomic ppm; these elevated nitrogen contents combined with the close association to eclogites suggest an eclogitic or crustal volatile source. However, the Karelian craton was periodically intruded by ultramafic alkaline magmas since at least 1.8 Ga, noting in particular the occurrence of phlogopite

  12. Aulacogens, the Donets Basin (Eastern Ukraine, Southwestern Russia, and the new classification of rifts: Towards a proper terminology

    Directory of Open Access Journals (Sweden)

    Ruban Dmitry A.

    2012-01-01

    Full Text Available Some intra-cratonic basins are traditionally called “aulacogens”. This term has persisted in the geoscience literature since its invention by Soviet geologists in the mid-20th century before the triumph of the plate tectonics, but its meaning has evolved. Attempts to change its meaning from descriptive to genetic have led to a broad spectrum of opinions on the definition of aulacogens. Some specialists related them to continental rifts, while others have restricted aulacogens to the only particular rift systems or peculiar stages in the evolution of young cratons. The Donets Basin is a typical aulacogen stretching across the southern margin of the East European Craton. A brief review of present knowledge of this basin shows that its nature is rather incompatible with the present understanding of aulacogens. Instead, the new classification of rifts offers a more precise terminology for its exact characteristics. It is suggested that the term “aulacogen” should only be restricted to those basins for which it has been applied historically.

  13. Preliminary study of geotectonic evolution of the southern region of Sao Francisco (MG, Brazil) craton: an interpretation based on Rb-Sr, K-Ar, Pb-Pb and fission track data

    International Nuclear Information System (INIS)

    Teixeira, W.; Fonseca, A.C.; Poupeau, G.; Padilha, A.V.; Zapparolli, L.H.; Kawashita, K.; Khoury, M.C.

    1985-01-01

    The results obtained from isotopic dating techniques (Rb-Sr, K-Ar, Pb-Pb and fission tracks) applied to samples from the southern region of Sao Francisco craton (Mg, Brazil) are discussed. Rb-Sr and Pb-Pb ages, in total rock, allowed the determination of crust enlargement, with eventual modifications of the pre-existing crust, during the Late Archean period (3000 to 2600 million years) and the Inferior Proterozoic period (2400 to 2100 m.y.). Three main cooling periods of time were determined by K-Ar dating of mica, amphiboles and total rock at the craton border: 2200 to 1700 m.y., 1300 to 1100 m.y. and 900 to 400 m.y. related, respectively, to superposition of three cycles: Transamazonico, Uruacuano and Brasiliano. Cooling below 110 0 C, detected by the fission track method applied to apatites, pointed out an age of 850 m.y. at the internal parts and 550 m.y. at the craton periphery, thus showing a progressive action of Brazilian marginal movable zones in the studied region. The application of these two techniques together enabled the evaluation of the rocks cooling shape. Cooling of these samples was complex between 2700 and 2200 m.y. and slow from 2000 m.y. onwards. The integrated treatment of data from the various dating techniques is of great importance to know the geotectonic evolution of ancient polycyclic sites. (C.L.B.) [pt

  14. EARLY STAGE OF THE CENTRAL ASIAN OROGENIC BELT BUILDING: EVIDENCES FROM THE SOUTHERN SIBERIAN CRATON

    Directory of Open Access Journals (Sweden)

    D. P. Gladkochub

    2017-01-01

    Full Text Available The origin of the Central-Asian Orogenic Belt (CAOB, especially of its northern segment nearby the southern margin of the Siberian craton (SC is directly related to development and closure of the Paleo-Asian Ocean (PAO. Signatures of early stages of the PAO evolution are recorded in the Late Precambrian sedimentary successions of the Sayan-Baikal-Patom Belt (SBPB on the southern edge of SC. These successions are spread over 2000 km and can be traced along this edge from north-west (Sayan area to south-east (Baikal area and further to north-east (Patom area. Here we present the synthesis of all available and reliable LA-ICP-MS U-Pb geochronological studies of detrital zircons from these sedimentary successions.

  15. A constrained African craton source for the Cenozoic Numidian Flysch: Implications for the palaeogeography of the western Mediterranean basin

    Science.gov (United States)

    Thomas, M. F. H.; Bodin, S.; Redfern, J.; Irving, D. H. B.

    2010-07-01

    The provenance of the Numidian Flysch in the western Mediterranean remains a controversial subject which hinders understanding of this regionally widespread depositional system. The Numidian Flysch is a deep marine formation dated as Oligocene to Miocene which outcrops throughout the Maghreb and into Italy. Evidence that is widely used for provenance analysis has not previously been reviewed within the context of the Maghrebian Flysch Basin as a whole. The structural location within the Alpine belt indicates deposition proximal to the African margin, while the uniformity of the Numidian Flysch petrofacies suggests a single cratonic source, in stark contrast to heterolithic and immature flysch formations from the north of the basin. Detrital zircon ages constrain a source region with Pan-African and Eburnian age rocks, unaffected by either Hercynian or Alpine tectonic events, which precludes the European basement blocks to the north of the basin. Palaeocurrent trends which suggest a northern source are unreliable given foreland basin analogues and observed structural complications. An African craton source remains the only viable option once these data are reviewed in their entirety, and the Numidian Flysch therefore represents a major Cenozoic drainage system on the North African margin. Deposition is concurrent with regional Atlas uplift phases, and coincidental with globally cooling climates and high sea levels. The Numidian Flysch is therefore interpreted to represent a highstand passive margin deposit, with timing of deposition controlled primarily by hinterland uplift and climatic fluctuations.

  16. New SHRIMP U-Pb zircon ages of the metapelitic granulites from NW of Madurai, Southern India

    International Nuclear Information System (INIS)

    Prakash, D.

    2010-01-01

    Zircon cathodoluminescent imaging and SHRIMP U-Pb dating were carried out for metapelitic rocks (sapphirine-hearing granulites and garnet-cordierite gneisses) from the NW of Madurai, Southern India. The cathodoluminescence images reveal the complex, inhomogeneous internal structure having irregular-shaped core and overgrowths. Zircon grains have obliterated oscillatory zoning. SHRIMP U-Pb chronological results yield ages of 550 ± 15 Ma and 530 ± 50 Ma as a time of metamorphic overprint, and the age of 2509 ± 12 Ma and 2509 ± 30 Ma corresponding to a timing of protolith formation for sapphirine-bearing granulites and garnet-cordierite gneisses respectively. Zircon ages reflect that continental crust in the NW of Madurai region resulted from the recycling of Archaean protolith of an igneous origin similar to the preserved crust in the southern part of Dharwar craton. The present SHRIMP U-Pb zircon ages are in close agreement with earlier published Nd isotopic data which suggest an extended precrustal history of their protoliths. The abraded zircon grains indicate multiple recycling and repeated metamorphism that has ultimately resulted in present day continental crust exposed in Madurai region. These SHRIMP U-Pb zircon ages from metapelitic UHT granulites are also significant to understanding the architecture of the SGT during the amalgamation of Gondwana in Neoproterozoic time. (author)

  17. Present-day geothermal characteristics of the Ordos Basin, western North China Craton: new findings from deep borehole steady-state temperature measurements

    Science.gov (United States)

    Gao, Peng; Qiu, Qianfeng; Jiang, Guangzheng; Zhang, Chao; Hu, Shengbiao; Lei, Yuhong; Wang, Xiangzeng

    2018-07-01

    Heat flow and associated thermal regimes are related to the tectonic evolution and geophysical properties of the lithosphere. The Ordos Basin is located in a tectonic transitional zone: areas to the east of the basin are characterized as tectonically active, while regions to the west of the basin are characterized as tectonically stable. It is of general interest to learn the geothermal characteristics of the basin in such tectonic conditions. To clarify the spatial variability of the present-day geothermal field across the basin and its implications, we report 13 terrestrial heat flow points based on the first systematic steady-state deep borehole temperature measurements in the basin. The new data together with existing data show that the geothermal gradients in the basin range from 12.6 to 42.3 °C km-1 with a mean of 27.7 ± 5.3 °C km-1; the terrestrial heat flow values range from 43.3 to 88.7 mW m-2 with a mean of 64.7 ± 8.9 mW m-2. Such values are higher than those of typical cratonic basins and lower than those of tectonically active areas. By using all these data in the basin and adjacent areas, we plot geothermal gradient and heat flow distribution maps. The maps reveal that the basin is cooling westwards and northwards. The distribution pattern of the geothermal field is consistent with the lithospheric thickness variation in the basin. This similarity suggests that the geothermal spatial variability of the Ordos Basin is mainly influenced by heat from the deep mantle. In the southeastern basin, we locate a positive geothermal anomaly caused by the convergence of heat flow in basement highs and the high radiogenic heat production. In addition, the high heat flow in the eastern basin is related to the intense uplift during the Cenozoic Era.

  18. Present-day geothermal characteristics of the Ordos Basin, western North China Craton: new findings from deep borehole steady-state temperature measurements

    Science.gov (United States)

    Gao, Peng; Qiu, Qianfeng; Jiang, Guangzheng; Zhang, Chao; Hu, Shengbiao; Lei, Yuhong; Wang, Xiangzeng

    2018-03-01

    Heat flow and associated thermal regimes are related to the tectonic evolution and geophysical properties of the lithosphere. The Ordos Basin is located in a tectonic transitional zone: areas to the east of the basin are characterized as tectonically active, while regions to the west of the basin are characterized as tectonically stable. It is of general interest to learn the geothermal characteristics of the basin in such tectonic conditions. To clarify the spatial variability of the present-day geothermal field across the basin and its implications, we report 13 terrestrial heat flow points based on the first systematic steady-state deep borehole temperature measurements in the basin. The new data together with existing data show that the geothermal gradients in the basin range from 12.6 to 42.3° C km-1 with a mean of 27.7 ± 5.3° C km-1; the terrestrial heat flow values range from 43.3 to 88.7 mW/m2 with a mean of 64.7 ± 8.9 mW/m2. Such values are higher than those of typical cratonic basins and lower than those of tectonically active areas. By using all these data in the basin and adjacent areas, we plot geothermal gradient and heat flow distribution maps. The maps reveal that the basin is cooling westward and northward. The distribution pattern of the geothermal field is consistent with the lithospheric thickness variation in the basin. This similarity suggests that the geothermal spatial variability of the Ordos Basin is mainly influenced by heat from the deep mantle. In the southeastern basin, we locate a positive geothermal anomaly caused by the convergence of heat flow in basement highs and the high radiogenic heat production. In addition, the high heat flow in the eastern basin is related to the intense uplift during the Cenozoic Era.

  19. Trace element and isotopic compositions of Vietnamese basalts: implications for mantle dynamics in the southeast Asian region

    International Nuclear Information System (INIS)

    Nguyen, H.; Fower, M.; Nguyen, H.; Nguyen, X.B.; Nguyen, T.Y.

    1996-01-01

    Cenozoic basalts in Indo-China are part of a regional melting episode along the rifted Eurasian margin. Trace element and isotopic compositions of Vietnamese basalts are used to place constraints on the extent of lithospheric and asthenosphere contributions to the melts and possible mantle dynamic implications. The 87 Sr/ 86 Sr, 207 Pb/ 204 Pb, and 208 Pb/ 204 Pb isotopic ratios of the basalts reflect minimal crustal wall rock reaction, and variable enrichment in EM1 and EM2 of a 208 Pb-rich MORB-like source. Some, but not all, of this variation corresponds to the age of lithospheric sector penetrated. Basalts erupted through a cratonic, central sector (e.g. at Quang Ngai, Pleiku, Song Cau, Kong Plong, and Buon Ma Thuot) and off-cratonic, southwest sector (e.g. Phuoc Long) resemble those of EM2-rich basalts from southern and southeaster China and the South China Sea. Basalts from an off-cratonic, southeast sector (e.g. from Dalat, Xuan Loc, and the offshore Ile des Cendres-Phu Cuy complex) reflect mixing between a low- 206 Pb/ 204 Pb, high- 208 Pb/ 204 Pb, EM1-like component, and resemble basalts from northwest Taiwan, eastern and northeastern China, and parts of the Japan Sea. While EM2 tends to characterise lithospheric sectors, presence of EM1 in off-cratonic rather than cratonic basalts implies an asthenosphere rather than lithospheric source. Pervasive presence of EM1 in southeast Asian and marginal basin asthenosphere corresponds with thermally-anomalous mantle and may involve delaminated cratonic substrate entrained by mobile, extruded asthenosphere. (authors)

  20. Journal of Earth System Science | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Trace, rare earth elements (REE), Rb-Sr, Sm-Nd and O isotope studies have been carried out on ultramafic (harzburgite and lherzolite) dykes belonging to the newer dolerite dyke swarms of eastern Indian craton. The dyke swarms were earlier considered to be the youngest mafic magmatic activity in this region having ages ...

  1. Seismic Refraction & Wide-angle Reflection Experiment on the Northern Margin of North China Craton -Data Acquisition and Preliminary Processing Result

    Science.gov (United States)

    Li, W.; Gao, R.; Keller, G. R.; Hou, H.; Li, Q.; Cox, C. M.; Chang, J. C.; Zhang, J.; Guan, Y.

    2010-12-01

    The evolution history of Central Asian Orogen Belt (CAOB) is still the main tectonic problems in northeastern Asia. The Siberia Craton (NC), North China Craton (NCC) and several blocks collided, and the resulting tectonic collage formed as the Paleo-Asian Ocean disappeared. Concerning the northern margin of North China Craton, many different geological questions remain unanswered, such as: the intracontinental orogenic process in the Yanshan orogen and the nature and location of the suture between the southern NC and the northern NCC. In Dec 2009, a 400 km long seismic refraction and wide-angle reflection profile was completed jointly by Institute of Geology, CAGS and University of Oklahoma. The survey line extended from the west end of the Yanshan orogen, across a granitoid belt to the Solonker suture zone. The recording of seismic waves from 8 explosions (500~1500 kg each) was conducted in four deployments of 300 Reftek125 (Texan) seismic recorders, with an average spacing of 1 km. For the calculations, we used the Rayinvr, Vmed and Zplot programs for ray tracing, model modification and phase picking. The initial result show that: 1)the depth of low velocity sediment cover ranges from 0.6 to 2.7 km (velocity: 2.8~5.6 km/s); 2)the depth of basement is 5.6~10 km (the depth of basement under the granitoid belt deepens to 10 km and velocity increases to 6.2 km/s); 3)the upper crust extends to a depth of 15.5~21 km and has the P-wave velocities between 5.6 and 6.4 km/s; 4)the thickness of the lower crust ranges from 22~28 km(velocity: 6.4~6.9 km/s); and 5)the depth of Moho varies from 39.5 km under the granitoid belt to 49 km under the Yanshan orogen. Based on these results, we can preliminarily deduce that: 1) the concave depression of the Moho observed represents the root of the Yanshan orogen, and it may prove that the orogen is dominated by thick-skinned tectonics; 2) the shape of velocity variations under the granitoid belt is suggestive of a magma conduit. It

  2. Linking craton stability and deep earth processes using thermochronology; a case study in the Superior Province of the Canadian Shield.

    Science.gov (United States)

    Sturrock, C. P.; Flowers, R. M.; Zhong, S.; Metcalf, J. R.; Kohn, B. P.

    2017-12-01

    Ancient, cratonic continental interiors are often presumed to be stable in the long term, neither accumulating nor shedding significant amounts of overlying sediment. However, recent low-temperature thermochronologic work suggests that such long term stability is an overly simplistic view and that forces besides plate tectonics, such as dynamic topography, may play a significant role. New apatite (U-Th)/He (AHe) and apatite fission track (AFT) data from Archean-Proterozoic basement rocks along a 1400km NW-SE transect in the Superior Province of the Canadian Shield record a spatially variable thermal history for the craton in Paleozoic through the end of Mesozoic time. Dates range from 600­­­­­­±60 Ma (AHe) and 529­±48 Ma (AFT) in the west to 184±14 Ma (AHe) and 174±9 Ma (AFT) in the east. Tectonic activity within the Superior Province ceased by 1.8 Ga, with the latest activity at the margins ending at 1 Ga. Widespread resetting of both AHe and AFT systems post 1 Ga is most likely due to regional scale burial at one or more times since the Cambrian. The temperature sensitivity of the AHe and AFT systems (30-90°C and 60-120°C, respectively) require at least a few km of burial across the craton that has since been stripped away. Preliminary inverse thermal history models, utilizing geologic constraints and radiation damage effects on He diffusion in apatite, indicate significant reheating in the Paleozoic-early Mesozoic (37 to >120°C) and a possible lesser reheating event since the mid Mesozoic (geothermal gradient and 0°C surface temperature, burial in some areas must have been at least 2-5km in the Paleozoic and was <4km in the Mesozoic. These burial and denudation patterns do not correlate with global sea level changes, making dynamic topography a good candidate for a driving mechanism. New AHe data from kimberlites emplaced in the early to mid-Jurassic will provide an important new constraint on the post-Jurassic thermal history of the Superior

  3. Assessing health literacy in the eastern and middle-eastern cultures

    Directory of Open Access Journals (Sweden)

    Satish Chandrasekhar Nair

    2016-08-01

    Full Text Available Abstract Background Health literacy is a term employed to assess the ability of people to meet the increasing demands related to health in a rapidly evolving society. Low health literacy can affect the social determinants of health, health outcomes and the use of healthcare services. The purpose of the study was to develop a survey construct to assess health literacy within the context of regional culture. Different socioeconomic status among the Eastern and Middle Eastern countries may restrict, health information access and utilization for those with low literacy. Methods By employing expert panel, Delphi technique, focus group methodologies, and pre-testing using participants (N = 900 from the UAE and India, a survey construct to the Eastern-Middle Eastern cultures was developed. Reliability was assessed using Cronbach’s α and validity using Factor analysis. Kiaser-Meyer-Olkin (KMO sampling adequacy and Bartlett’s tests were used to assess the strength of the relationship among the variables. Results Inclusion of non-health related items were found to be critical in the authentic assessment of health literacy in the Eastern and Middle Eastern population given the influence of social desirability. Thirty-two percentage of the original 19-item construct was eliminated by the focus group for reasons of relevance and impact for the local culture. Field pretesting participants from two countries, indicated overall construct reliability (Cronbach’s α =0.85, validity and consistency (KMO value of 0.92 and Bartlett’s test of sphericity was significant. Conclusion The Eastern-Middle Eastern Adult Health Literacy (EMAHL13, screening instrument is brief, simple, a useful indicator of whether or not a patient can read. It assessespatients’ ability to comprehend by distinguishing between health and non-health related items. The EMAHL13 will be a useful too for the reliable assessment of health literacy in countries, where culture plays a

  4. Assessing health literacy in the eastern and middle-eastern cultures.

    Science.gov (United States)

    Nair, Satish Chandrasekhar; Satish, Karthyayani Priya; Sreedharan, Jayadevan; Ibrahim, Halah

    2016-08-19

    Health literacy is a term employed to assess the ability of people to meet the increasing demands related to health in a rapidly evolving society. Low health literacy can affect the social determinants of health, health outcomes and the use of healthcare services. The purpose of the study was to develop a survey construct to assess health literacy within the context of regional culture. Different socioeconomic status among the Eastern and Middle Eastern countries may restrict, health information access and utilization for those with low literacy. By employing expert panel, Delphi technique, focus group methodologies, and pre-testing using participants (N = 900) from the UAE and India, a survey construct to the Eastern-Middle Eastern cultures was developed. Reliability was assessed using Cronbach's α and validity using Factor analysis. Kiaser-Meyer-Olkin (KMO) sampling adequacy and Bartlett's tests were used to assess the strength of the relationship among the variables. Inclusion of non-health related items were found to be critical in the authentic assessment of health literacy in the Eastern and Middle Eastern population given the influence of social desirability. Thirty-two percentage of the original 19-item construct was eliminated by the focus group for reasons of relevance and impact for the local culture. Field pretesting participants from two countries, indicated overall construct reliability (Cronbach's α =0.85), validity and consistency (KMO value of 0.92 and Bartlett's test of sphericity was significant). The Eastern-Middle Eastern Adult Health Literacy (EMAHL13), screening instrument is brief, simple, a useful indicator of whether or not a patient can read. It assessespatients' ability to comprehend by distinguishing between health and non-health related items. The EMAHL13 will be a useful too for the reliable assessment of health literacy in countries, where culture plays a significant impact. This will be the first steptowards providing

  5. Eastern Europe

    International Nuclear Information System (INIS)

    Baret, J.P.; Corcuff, A.; Jousten, M.; Cherie, J.B.; Gorge, X.; Augustin, X.; Belime, F.

    1999-01-01

    By its economical and political impact, nuclear energy has an important contribution the countries of Eastern Europe that goes beyond simple energy source. The most important challenge is to gain a safety culture. Improvements have been noted but the reactors safety must stay a priority of the international cooperation in Eastern Europe. The plan for the completion and improvement of Mochovce nuclear plant is described, the situation of Chernobyl and how to make the sarcophagus in safe is discussed, the experience of a french P.M.E. ( small and medium size firm) called Corys Tess that has chosen to position itself on the Eastern Europe nuclear market is related. (N.C.)

  6. The peculiar case of Marosticano xenoliths: a cratonic mantle fragment affected by carbonatite metasomatism in the Veneto Volcanic Province (Northern Italy)

    Science.gov (United States)

    Brombin, Valentina; Bonadiman, Costanza; Coltorti, Massimo; Florencia Fahnestock, M.; Bryce, Julia G.; Marzoli, Andrea

    2017-04-01

    The Tertiary Magmatic Province of Veneto, known as Veneto Volcanic Province (VVP), in the Northern Italy, represents one of the most important volcanic provinces of the Adria Plate. It is composed by five volcanic districts: Val d'Adige, Marosticano, Mts. Lessini, Berici Hills and Euganean Hills. Most of the volcanic products are relatively undifferentiated lavas, from nephelinites to tholeiites in composition. Commonly VVP nephelinites and basanites carry mantle xenoliths. This study presents a petrological characterization of the new xenolith occurrence of Marosticano and comparison with previously studied VVP xenolith populations (i.e. from the Lessinean and Val d'Adige areas), which represent off-craton lithospheric mantle fragment affected by Na-alkaline silicate metasomatism (Siena & Coltorti 1989; Beccaluva et al., 2001; Gasperini et al., 2006). Marosticano (MA) peridotites are anhydrous spinel-bearing lherzolites and harzburgites, which are geochemically well distinguishible from the other VVP mantle xenoliths. Primary minerals record the "most restitic" composition of the VVP sampled mantle, even calling the geochemical features of a sub-cratonic mantle. Olivines in both lherzolites and harzburgites show high Ni contents compared with the Fo values (Ni→ lherzolite: 2600-3620 ppm; harzburgite: 2600-3540 ppm; Fo → lh: 91-92; hz: 90-93) that follow the trend of olivine from a cratonic area (Kelemen, 1998). Orthopyroxenes have mg# values with 1:1 ratio with coexisting olivines and Al2O3 contents always 0.5 wt%) contents are also the chemical characteristics of the clinopyroxenes. On the whole both MA pyroxenes show major element contents that recall the characteristics of those from cratonic (sp-bearing) peridotites (e.g. from Greenland, South Africa and Tanzania; Downes et al., 2004). In addition, the relationship between the high Fo content of olivine and the high chromium contents (cr#=(Cr/(Cr+Al)X100); lh: 30-53; hz: 38-67) in coexisting spinel, out of

  7. Identification of thermotectonics events by 40Ar/39Ar methodology, in Jauru, Pontes e Lacerda and Rio Alegre Terrane - southwest portion of Amazon Craton

    International Nuclear Information System (INIS)

    Paulo, Valeria Guimaraes de

    2005-01-01

    The southwest portion of Amazon Craton, subject of these work, correspond to the southwest region of Mato Grosso State and is inserted on Rio Negro-Juruena, Rondoniana-San Ignacio and Sunsas-Aguapei geochronologic Provinces. This region is surrounded by three big terranes: Jauru, Pontes e Lacerda and Rio Alegre. The main aim of this study is to use the ages of termochronologic events obtained by 40 Ar/ 39 Ar methodology, including data of literature, to contribute with the study of the geotectonic evolution on this region. Twenty samples were analyzed and 40 Ar/ 39 Ar ages found for the Jauru Terrane vary of 1539 ± 3 Ma to 1338 ± 3 Ma, for the Pontes e Lacerda Terrane the interval obtained was of 946,1 ± 0,8 Ma to 890 ± 2 Ma and for Rio Alegre Terrane the ages are between 1407 ± 3 Ma to 1321 ± 2 Ma. U/Pb, Rb/Sr and Sm/Nd data from previous works, together with 40 Ar/ 39 Ar results allowed to obtain cooling average rates to each terrane. The Jauru Terrane units cooling age is equivalent to 1,52 Ga. The cooling average rates found to Alto Jauru Greenstone belt rocks is 2,4 deg C - 1,0 Ma and to Magmatic Arc Cachoeirinha is 10,8 deg C - 1,0 Ma. Stabilization age obtained for Pontes and Lacerda Terrane is about 900 Ma coherent with the cooling age of the Sunsas Aguapei Event (1,0 - 0,9 Ga) and cooling average rates calculate were the lower, equivalent to 1,0 deg C - 1,0 Ma. Cooling age found in Rio Alegre Terrane was 1,35 Ga, possibility correspond to collision age these terrane with Amazonian protoCraton and cooling average rates of 5,0 deg C - 1,0 Ma. Finally, younger age found of 900 Ma, coherent to the Sunsas - Aguapei Event, probably represent the last regional event that affected these rocks, characterizing the stabilization period of the southwest portion of Amazon Craton. (author)

  8. Pangea: Geochronological correlation of successive environmental and strati-tectonic phases in Europe and Australia

    Science.gov (United States)

    Veevers, J. J.

    2013-12-01

    A robust geochronology based on U-Pb zircon ages in Australia (n = 158) and Europe (n = 376) provides a rigorous test of (1) the model of a climatic-tectonic cycle of a single continent (Pangea) and ocean (Panthalassa) with an icehouse climate alternating with many continents and oceans with a greenhouse climate, and (2) the idea of coeval (320 to 300 Ma) right-lateral shear events in Eastern Australia and Europe followed by earliest Permian (~ 300 Ma) extension. During Pangean assembly, stress from the oblique collision of Laurussia and Gondwanaland bent the oroclines in Iberia, drove the intense shortening in Central Australia and terminal megakinking in the Lachlan orogen, and possibly drove the bending of oroclines in Eastern Australia. Extension I (~ 300 Ma, Carboniferous/Permian) followed the first outburst of self-induced (monsoonal) heat from the newly assembled Pangea, and generated fresh accommodation space for globally synchronous sedimentary successions, including the glacial base and succeeding coals of the Gondwana facies. Extension was relieved by sags on (isotropic) cratons and rifts on (anisotropic) fold belts with voluminous volcanics. In Europe, the Variscan orogen was cut into right-lateral magmatic rifts and the craton sagged to accumulate magmatic basins; likewise, the convergent margin of Eastern Australia was cut into a long magmatic rift and the cratonic foreland covered by the Gondwana facies. The end-Permian (251 Ma) sea-level drawdown, climate warming, and severe biotic extinction, with no obvious tectonic cause, were responsible for the Early-Middle Triassic coal gap. A second outburst of heat drove Extension II (235 Ma, Carnian, Late Triassic), expressed as rifts and sags that accumulated a second set of coal-bearing strata. At this time of its largest extent, Pangea underwent incipient breakup by rifting of the Atlantic Margins of North America, Morocco, and Western Europe that developed into 190 Ma drifting.

  9. NEW LATE JURASSIC PALEOMAGNETIC RESULTS FROM SHARILYN FORMATION, SOUTHERN MONGOLIA, AMURIA BLOCK, AND THEIR IMPLICATIONS FOR THE TECTONIC EVOLUTION OF THE MONGOL–OKHOTSK SUTURE

    Directory of Open Access Journals (Sweden)

    Qiang Ren

    2017-01-01

    Full Text Available The Amuria block occupies the eastern part of the Central Asian Orogenic Belt between the Siberia craton and the North China block (NCB and bears important information to understand the evolution of the MongolOkhotsk suture and the amalgamation of East Asia. However, the paleomagnetic database of Amuria remains very poor.

  10. Petrological study of the eastern part of Rio Maria batholith located in the SE of Para State

    International Nuclear Information System (INIS)

    Medeiros, H. de.

    1987-01-01

    This work is a petrological and geochronological study in the eastern part of Rio Maria batholith located in the SE of Para State (Brazil), in which granodioritic composition predominates. Selected samples including all varieties present in the eastern portion of Rio Maria granodioritic batholith were analyzed for major, minor and some trace elements. The results suggest two differentiation trends. The first is (BHGd + HBGd) - HBM sub(z)G, with decrease in CaO, TiO sub(2), Fe total, MgO and Sr contents, whereas K2O and Rb increase. The second trend is (BHGd + HBGd) - BGd, where the BGd have the highest values of SiO sub(2), and low CaO, TiO sub(2), Fe total, MgO and Sr contents. This results are in agreement with that obtained to the calc-alkaline rock series. Six selected samples, including all varieties, were dated by the Rb/Sr Whole-rock method, producing a isochronic age of 2564 +- 68 m.y. with an initial Sr sup(87)/Sr sup(86) ratio of 0.70288 +- 00092. The crystallization sequence proposed to the BHGd and BHGd, when correlated to the experimental results obtained in the rocks of granodioritic composition, suggests that the magma crystallization was in low pressure conditions (2 to 4kb). The temperature interval would be between 950 and +- 700 sup(0)C. The best explanation to the granodioritic magma origin is by partial fusion in the crustal base, with contribution of mantle material or not. The association of the rock units, including granodiorites, trondhjemites, meta-volcan-sedimentary sequences and gneisses of tonalitic to granodioritic composition observed in the Rio Maria region, and the Archaeyan ages obtained by the Rb/Sr method suggest that this region can be correlated with granite-greenstone terrains exposed in the Rhodesian, Kaapvaal and western Australia cratons. (author)

  11. Low temperature thermochronology and topographic evolution of the South Atlantic passive continental margin in the region in eastern Argentina

    Science.gov (United States)

    Pfister, Sabrina; Kollenz, Sebastian; Glasmacher, Ulrich A.

    2014-05-01

    To understand the evolution of the passive continental margin in Argentina low temperature thermochronology is an appropriate method, which will lead to new conclusions in this area. The Tandilia System, also called Sierras Septentrionales, is located south of the Río de la Plato Craton in eastern Argentina in the state of Buenos Aires. North of the hills Salado basin is located whereas the Claromecó basin is situated south of the mountain range. In contrary to most basins along the southamerican passive continental margin the Tandilia-System and the neighbouring basins trend perpendicular to the coast line. The topography is fairly flat with altitudes of. The igneous-metamorphic basement is pre-proterozoic in age and build up of mainly granitic-tonalitic gneisses, migmatites, amphibolites, some ultramafic rocks and granitoid plutons it is overlain by a series of Neoproterozoic to early Paleozoic sediments (Cingolani, 2010), like siliciclastics, dolostones, shales and limestones (Demoulin et al., 2005). The aim of the study is to quantify the long-term landscape evolution of the passive continental margin in eastern Argentina in terms of thermal history, exhumation and tectonic activities. For that purpose, samples were taken from the Sierra Septentrionales and analyzed with the apatite fission-track method. Further 2-D thermokinematic modeling was conducted with the computer code HeFTy (Ketcham, 2005; Ketcham 2007; Ketcham et al., 2009). The results indicate apatite fission track ages between 101.6 (9.4) to 228.9 (22.3) Ma, what means all measured ages are younger as their formation age. That shows all samples have been reset. Six samples accomplished enough confined tracks and were used to test geological t-T models against the AFT data set. These models give a more detailed insight on the cooling history and tectonic activities in the research area. References: Cingolani C. A. (2010): The Tandilia System of Argentina as a southern extension of the Río de la

  12. Crustal Poisson’s ratio anomalies in the eastern part of North China and their origins

    Directory of Open Access Journals (Sweden)

    Wencai Yang

    2011-07-01

    Full Text Available Seismic tomography can provide both fine P-wave and S-wave velocity structures of the crust and upper mantle. In addition, with proper computation, Poisson’s ratio images from the seismic velocities can be determined. However, it is unknown whether Poisson’s ratio images have any advantages when compared with the P-wave and S-wave velocity images. For the purposes of this study, high-resolution seismic tomography under the eastern part of North China region was used to determine detailed 3-D crustal P- and S-wave seismic velocities structure, as well as Poisson’s ratio images. Results of Poisson’s ratio imaging show high Poisson’s ratio (high-PR anomalies located in the Hengshan-North Taihang-Zhangjiakou (H-NT-Z region, demonstrating that Poisson’s ratio imaging can provide new geophysical constraints for regional tectonic evolution. The H-NT-Z region shows a prominent and continuous high-PR anomaly in the upper crust. Based on Poisson’s ratio images at different depths, we find that this high-PR anomaly is extending down to the middle crust with thickness up to about 26 km. According to rock physical property measurements and other geological data, this crustal Poisson’s ratio anomaly can be explained by Mesozoic partial melting of the upper mantle and basaltic magma underplating related to the lithospheric thinning of the North China craton.

  13. Trace element and isotopic compositions of Vietnamese basalts: implications for mantle dynamics in the southeast Asian region; Compositions isotopiques et en elements en trace des basaltes vietnamiens: implications pour la dynamique du manteau en Asie du Sud-Est

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, H.; Fower, M. [Illinois Univ., Chicago, IL (United States); Nguyen, H. [Tokyo Univ. (Japan); Nguyen, X.B.; Nguyen, T.Y. [Institute of Nuclear Science and Technology, Hanoi (Viet Nam)

    1996-12-31

    Cenozoic basalts in Indo-China are part of a regional melting episode along the rifted Eurasian margin. Trace element and isotopic compositions of Vietnamese basalts are used to place constraints on the extent of lithospheric and asthenosphere contributions to the melts and possible mantle dynamic implications. The {sup 87}Sr/{sup 86}Sr, {sup 207}Pb/{sup 204}Pb, and {sup 208}Pb/{sup 204}Pb isotopic ratios of the basalts reflect minimal crustal wall rock reaction, and variable enrichment in EM1 and EM2 of a {sup 208}Pb-rich MORB-like source. Some, but not all, of this variation corresponds to the age of lithospheric sector penetrated. Basalts erupted through a cratonic, central sector (e.g. at Quang Ngai, Pleiku, Song Cau, Kong Plong, and Buon Ma Thuot) and off-cratonic, southwest sector (e.g. Phuoc Long) resemble those of EM2-rich basalts from southern and southeaster China and the South China Sea. Basalts from an off-cratonic, southeast sector (e.g. from Dalat, Xuan Loc, and the offshore Ile des Cendres-Phu Cuy complex) reflect mixing between a low- {sup 206}Pb/{sup 204}Pb, high-{sup 208}Pb/{sup 204}Pb, EM1-like component, and resemble basalts from northwest Taiwan, eastern and northeastern China, and parts of the Japan Sea. While EM2 tends to characterise lithospheric sectors, presence of EM1 in off-cratonic rather than cratonic basalts implies an asthenosphere rather than lithospheric source. Pervasive presence of EM1 in southeast Asian and marginal basin asthenosphere corresponds with thermally-anomalous mantle and may involve delaminated cratonic substrate entrained by mobile, extruded asthenosphere. (authors) 85 refs.

  14. Episodic crustal growth in the Bundelkhand craton of central India ...

    Indian Academy of Sciences (India)

    Hiredya Chauhan

    2018-04-12

    Apr 12, 2018 ... geochemical features indicate formation of the K-granites by anhydrous partial melting of the Paleo- ...... A metamorphic episode from white mica schist is reported ...... monian G 2013 Central/eastern Indian Bundelkhand and.

  15. Pan African Collisional Tectonics Along the Moroccan West African Craton Continued to Ediacaran-Cambrian Boundary

    Science.gov (United States)

    Hefferan, K. P.; Samson, S. D.; Rice, K.; Soulaimani, A.

    2016-12-01

    Precision geochronologic dating and field mapping in the Anti-Atlas Mountains of Morocco document a Neoproterozoic Pan African orogenic cycle consisting of three distinct orogenic events: Iriri-Tichibanine orogeny (760-700 Ma), Bou Azzer orogeny (680-640 Ma) and the WACadomian orogeny (620 Ma to either 555 or 544 Ma). The Iriri-Tichibanine and Bou Azzer orogenies involved northward directed subduction beneath island arc volcanic terranes. These orogenic events generated calc-alkaline magmatism and supra-subduction zone ophiolites exposed in the Bou Azzer and Siroua erosional inliers. The WACadomian orogeny involved subduction and collision of the Cadomia arc complex with the West African Craton and generation of clastic sedimentary basins. The termination of the WACadomian orogeny has been the subject of debate as calc-alkaline to high K magmatism and folding continued to 544 Ma: Was 620-544 Ma calc-alkaline to high K magmatism and clastic basin development due to a) continental rift basin tectonics or b) southward directed subduction and collisional tectonics with associated back arc basin tectonism? We present field and geochemical data supporting the continuation of subduction-collisional tectonics to the Ediacaran-Cambrian boundary 544 Ma. Field mapping in the Central Anti-Atlas (Agadir Melloul) clearly documents an angular unconformity between Ouarzazate Group and Adoudounian limestones (N 30°31'28.91", W07°48'29.12"). Volcaniclastic rocks of Ouarzazate Group (615-545 Ma) are clearly folded and unconformably overlain by Adoudou Formation (541-529 Ma) limestones to the north. Geochemical discrimination diagrams on Latest Neoproterozoic calc-alkaline to high K igneous rocks throughout the Anti-Atlas plot in subduction and collisional arc magma domains. Back arc basin tectonism is likely responsible for localized extensional basins but continental rift tectonics and passive margin sedimentation did not begin in the Anti-Atlas Mountains until Early

  16. Paleoproterozoic volcanism in the southern Amazon Craton (Brazil): insight into its origin and deposit textures

    Science.gov (United States)

    Roverato, Matteo; Juliani, Caetano

    2014-05-01

    The Brazilian Amazon craton hosts a primitive volcanic activity that took place in a region completely stable since 1.87 Ga. The current geotectonic context is very different from what caused the huge volcanism that we are presenting in this work. Volcanic rocks in several portions of the Amazon craton were grouped in the proterozoic Uatumã supergroup, a well-preserved magmatic region that covers an area with more than 1,200,000 km2. In this work one specific region is considered, the southwestern Tapajos Gold province (TGP) that is part of the Tapajós-Parina tectonic province (Tassinari and Macambri, 1999). TGP consists of metamorphic, igneous and sedimentary sequences resulted from a ca. 2.10-1.87 Ga ocean-continent orogeny. High-K andesites to felsic volcanic sequences and plutonic bodies, andesitic/rhyolitic epiclastic volcanic rocks and A-type granitic intrusions form part of this volcanism/plutonism. In this work we focus particularly our attention on welded, reomorphic and lava-like rhyolitic ignimbrites and co-ignimbrite brecchas. Fiamme texture of different welding intensity, stretched obsidian fragments, "glassy folds", relict pumices, lithics, rotated crystals of feldspars, bipiramidal quarz, and devetrification spherulites are the common features represented by our samples. Microscopical images are provided to characterize the deposits analyzed during this preliminary research. The lack of continuum outcrops in the field made more difficult the stratigraphic reconstruction, but the superb preservation of the deposits, apparently without any metamorphic evidences (not even low-grade), permits a clearly description of the textures and a differentiation between deposits. A detailed exploration of this ancient andesitic and rhyolitic volcanic activity could contribute greatly to the knowledge of the Amazon territory and in particular for the recognition of the various units that form the supergroup Uatumã, especially in relation to different eruptive

  17. Provenance and tectonic significance of the Palaeoproterozoic metasedimentary successions of central and nothern Madagascar

    Science.gov (United States)

    De Waele, B.; Thomas, Ronald J.; Macey, P.H.; Horstwood, M.S.A.; Tucker, R.D.; Pitfield, P.E.J.; Schofield, D.I.; Goodenough, K.M.; Bauer, W.; Key, R.M.; Potter, C.J.; Armstrong, R.A.; Miller, J.A.; Randriamananjara, T.; Ralison, V.; Rafahatelo, J.-M.; Rabarimanana, M.; Bejoma, M.

    2011-01-01

    New detrital zircon U–Pb age data obtained from various quartzite units of three spatially separated supracrustal packages in central and northern Madagascar, show that these units were deposited between 1.8 and 0.8 Ga and have similar aged provenances. The distribution of detrital zircon ages indicates an overwhelming contribution of sources with ages between 2.5 and 1.8 Ga. Possible source rocks with an age of 2.5 Ga are present in abundance in the crustal segments (Antananarivo, Antongil and Masora Domains) either side of a purported Neoproterozoic suture ("Betsimisaraka Suture Zone"). Recently, possible source rocks for the 1.8 Ga age peak have been recognised in southern Madagascar. All three supracrustal successions, as well as the Archaean blocks onto which they were emplaced, are intruded by mid-Neoproterozoic magmatic suites placing a minimum age on their deposition. The similarities in detrital pattern, maximum and minimum age of deposition in the three successions, lend some support to a model in which all of Madagascar's Archaean blocks form a coherent crustal entity (the Greater Dharwar Craton), rather than an amalgamate of disparate crustal blocks brought together only during Neoproterozoic convergence. However, potential source terranes exist outside Madagascar and on either side of the Neoproterozoic sutures, so that a model including a Neoproterozoic suture in Madagascar cannot be dispelled outright.

  18. IAEA/WHO postal dose audits for radiotherapy hospitals in Eastern and South-Eastern Europe

    International Nuclear Information System (INIS)

    Izewska, J.; Vatnitsky, S.; Shortt, K.R.

    2004-01-01

    The IAEA/WHO TLD programme has been in operation for 34 years. In this period the calibration of approximately 5200 high-energy photon beams in over 1300 radiotherapy hospitals in 115 countries worldwide was checked. Of these, 18% of the audits were performed in Eastern and South-Eastern Europe. There are large contrasts in the region; while the results are very good for most countries, a few countries struggle with basic problems in dosimetry. The hospitals operating radiotherapy services without qualified medical physicists or dosimetry equipment have poorer results than those properly equipped and staffed. Only about 2/3 of TLD audit participants in Eastern Europe have the appropriate dosimetry equipment. To achieve consistency of the audit results within Eastern and South-Eastern Europe, strengthening of radiotherapy infrastructure in a few countries would be necessary. (authors)

  19. Seismic Anisotropy Beneath the Eastern Flank of the Rio Grande Rift

    Science.gov (United States)

    Benton, N. W.; Pulliam, J.

    2015-12-01

    Shear wave splitting was measured across the eastern flank of the Rio Grande Rift (RGR) to investigate mechanisms of upper mantle anisotropy. Earthquakes recorded at epicentral distances of 90°-130° from EarthScope Transportable Array (TA) and SIEDCAR (SC) broadband seismic stations were examined comprehensively, via the Matlab program "Splitlab", to determine whether SKS and SKKS phases indicated anisotropic properties. Splitlab allows waveforms to be rotated, filtered, and windowed interactively and splitting measurements are made on a user-specified waveform segment via three independent methods simultaneously. To improve signal-to-noise and improve reliability, we stacked the error surfaces that resulted from grid searches in the measurements for each station location. Fast polarization directions near the Rio Grande Rift tend to be sub-parallel to the RGR but then change to angles that are consistent with North America's average plate motion, to the east. The surface erosional depression of the Pecos Valley coincides with fast polarization directions that are aligned in a more northerly direction than their neighbors, whereas the topographic high to the east coincides with an easterly change of the fast axis.The area above a mantle high velocity anomaly discovered separately via seismic tomography which may indicate thickened lithosphere, corresponds to unusually large delay times and fast polarization directions that are more closely aligned to a north-south orientation. The area of southeastern New Mexico that falls between the mantle fast anomaly and the Great Plains craton displays dramatically smaller delay times, as well as changes in fast axis directions toward the northeast. Changes in fast axis directions may indicate flow around the mantle anomaly; small delay times could indicate vertical or attenuated flow.

  20. 75 FR 68397 - DeQueen and Eastern Railroad, LLC-Acquisition and Operation Exemption-DeQueen and Eastern...

    Science.gov (United States)

    2010-11-05

    ... Eastern Railroad, LLC--Acquisition and Operation Exemption--DeQueen and Eastern Railroad Company DeQueen and Eastern Railroad, LLC (DQE), a noncarrier, has filed a verified notice of exemption under 49 CFR 1150.31 to acquire from DeQueen and Eastern Railroad Company and to operate approximately 47 miles of...

  1. Deeply concealed half-graben at the SW margin of the East European Craton (SE Poland — Evidence for Neoproterozoic rifting prior to the break-up of Rodinia

    Directory of Open Access Journals (Sweden)

    P. Krzywiec

    2018-01-01

    Full Text Available Baltica was one of continents formed as a result of Rodinia break-up 850–550 Ma. It was separated from Amazonia(? by the Tornquist Ocean, the opening of which was preceded by Neoproterozoic extension in a network of continental rifts. Some of these rifts were subsequently aborted whereas the Tornquist Rift gave rise to splitting of Rodinia and formation of the Tornquist Ocean. The results of 1-D subsidence analysis at the fossil passive margin of Baltica provided insight in the timing and kinematics of continental rifting that led to break-up of Rodinia. Rifting was associated with Neoproterozoic syn-rift subsidence accompanied by deposition of continental coarse-grained sediments and emplacement of continental basalts. Transition from a syn-rift to post-rift phase in the latest Ediacaran to earliest early Cambrian was concomitant with deposition of continental conglomerates and arkoses, laterally passing into mudstones. An extensional scenario of the break-up of Rodinia along the Tornquist Rift is based on the character of tectonic subsidence curves, evolution of syn-rift and post-rift depocenters in time, as well as geochemistry and geochronology of the syn-rift volcanics. It is additionally reinforced by the high-quality deep seismic reflection data from SE Poland, located above the SW edge of the East European Craton. The seismic data allowed for identification of a deeply buried (11–18 km, well-preserved extensional half-graben, developed in the Palaeoproterozoic crystalline basement and filled with a Neoproterozoic syn-rift volcano-sedimentary succession. The results of depth-to-basement study based on integration of seismic and gravity data show the distribution of local NE–SW elongated Neoproterozoic depocenters within the SW slope of the East European Craton. Furthermore, they document the rapid south-eastwards thickness increase of the Neoproterozoic succession towards the NW–SE oriented craton margin. This provides evidence

  2. Area Studies and Eastern Europe: How Eastern Europe Collapsed

    Directory of Open Access Journals (Sweden)

    Mirjana Kasapović

    2007-01-01

    Full Text Available In the first part, the author outlines the development of area studies in contemporary comparative politics, and points to their importance for the development of political science. In the second part, she examines the methodology – research design and methods – of regional comparatistics, paying particular attention to the problem of defining the region as a central category in this field of comparative politics. The third and central part is focused on the emergence of Eastern Europe as a historical-political and socio-cultural region in the course of history, especially after World War II, and on its dissolution in the processes of democratic transformation of communist regimes in the last two decades. The dissolution of Eastern Europe has resulted in restoration of a tripartite political geography in the area which it used to take up, made up of Central Europe, Southeast Europe and the proper Eastern Europe.

  3. Komatiites and nickel sulfide ores of the Black Swan area, Yilgarn Craton, Western Australia. 4. Platinum group element distribution in the ores, and genetic implications

    Science.gov (United States)

    Barnes, Stephen J.

    2004-11-01

    The Black Swan komatiite sequence, in the Eastern Goldfields province of the Archaean Yilgarn Craton in Western Australia, is a body of dominantly olivine-rich cumulates with lesser volumes of spinifex textured rocks, interpreted as a section through an extensive komatiite lava flow field. The sequence hosts a number of nickel sulfide orebodies, including the Silver Swan massive shoot and the Cygnet and Black Swan disseminated orebodies. The massive sulfide orebodies of the Black Swan Succession are pervasively depleted in all platinum group elements (PGEs), particularly Pt and Pd, despite very high Ni contents. This depletion cannot be explained by R-factor variations, which would also require relatively low Ni tenors. The PGE depletion could be explained in part if the ores are enriched in a monosulfide solid solution (MSS) cumulate component, but requires some additional fractional segregation of sulfide melt upstream from the site of deposition. The Silver Swan orebody shows a remarkably consistent vertical zonation in PGE contents, particularly in Ir, Ru, Rh, Os, which increase systematically from very low levels at the stratigraphic base of the sulfide body to maxima corresponding roughly with the top of a lower layer of the orebody rich in silicate inclusions. Platinum shows the opposite trend, but is somewhat modified by remobilisation during talc carbonate alteration. A similar pattern is also observed in the adjacent White Swan orebody. This zonation is interpreted and modelled as the result of fractional crystallisation of MSS from the molten sulfide pool. The strong IPGE depletion towards the base of the orebody may be a consequence of sulfide liquid crystallisation in an inverted thermal gradient, between a thin rapidly cooling upper rind of komatiite lava and a hot substrate.

  4. THE SOUTHERN FRAGMENT OF THE SIBERIAN CRATON: “LANDSCAPE” HISTORY OVER TWO BILLION YEARS

    Directory of Open Access Journals (Sweden)

    Arkady M. Stanevich

    2010-01-01

    Full Text Available In the state-of-the-art geology, concepts of evolution of interrelated geodynamic and biotic events throughout the history of the Earth have been developed (Fig. 1. Research results on sediments, bio-stratigraphy and geodynamics of the southern fragment of the Siberian craton (SSC, Fig. 2 provide for more or less reliable assessments of the status and evolution of ancient landscapes and biotas from the Lower Proterozoic to the Cenozoic.In the Lower Proterozoic, the geodynamic regime of the Urik-Iyskiy graben was similar to those of the westernpacific island-arc systems, which resulted in the orogen formation and established post-orogen granitoids of 1.86 bln years of age. At the beginning of the Early Riphean, volcano-sedimentary masses were accumulated in continental basins (Fig. 2, 3A. Collision orogenesis also resulted in the occurrence of the terrigeno-volcanogenic complex of the Akitkanskaya suite in the Western Pribaikalie and the transecting Irelskiy granitoids, aged 1.86 bln years, at the edge of the craton. Later on, most probably before the Riphean, peneplanation took place, and a shallow peripheral sea was formed with highly-mature sediments of the Purpolskaya suite. Different environments are reconstructed in the KodarUdokan zone. Sediments of the Udokanskaya suite, varying in thicknesses from 11 to 14 km, suggest a complicated evolution of sedimentation in the peripheral marine basin. Dozens of radiochronological datings of granitoids of the Chuiskiy and Kodarskiy complex which transect the Udokanskaya suite are within the range from 1.7 to 2.0 bln years. From the deposit composition and texture, it can be suggested that the middle, Chineiskaya sub-suite was formed under island-arc conditions; and glacial phenomena occurred in the late Udokan time.Further geological history of the SSC can be described only within the period after the Late Riphean sedimentations (see Fig. 3Б, В. The SSC evolution in the Neo-Proterozoic began with

  5. U-Pb dating, geochemistry, and tectonic implications of the Songpan-Ganzi block and the Longmen Shan, Chiba

    International Nuclear Information System (INIS)

    Chen, Y.L.; Li, D.P.; Zhou, J.

    2009-01-01

    The Songpan-Ganzi triangular tectonic block is surrounded by the East Kunlun-Qaidam block in the north, the Qiangtang block in the southwest, and the Longmen Shan in the southeast. The Longmen Shan is the eastern margin of the Tibetan Plateau in Central Asia. The tectonic affinity and relationship of these regions with the Yangtze and North China blocks have been rigorously debated. In this paper, we present our recent studies on the geochemistry of the Precambrian to Triassic classic sedimentary rocks from this area. Detrital zircons were extracted from the sedimentary rocks for U-Pb dating by SHRIMP and LA-ICP-MS. Nd depleted mantle model ages indicate that these provenances have an affinity to the Yangtze craton and Qinling Shan, in contrast to those of the North China craton. All strata, from Cambrian to late Triassic, contain detrital zircon U-Pb ages of 1400 to 600 Ma, with most falling between 900-720 Ma. The Songpan-Ganzi block was the most important part of the Northern Tethys in the Triassic period, in addition to being the largest flysch basin in the world. The Longmen Shan thrust belt comprises both the telescoped, unmetamorphosed, shallow water carbonate-dominated passive margin of the Yangtze craton and its crystalline basement. The western and northern margins of the Yangtze craton, as well as the Qinling Shan, were the sources of sediments in the Songpan-Ganzi block and the Longmen Shan. The oldest dated detrital zircons indicate that the Yangtze craton started forming during the period 2800-2200 Ma. Because the basement of the Yangtze craton experienced multi-episodic intracrustal processes, the oldest basement components account for only a small portion of the provenance components. The detrital zircon ages of 2200-1400 Ma indicate a major contribution of the Qinling Shan and/or the northwestern margin of the Yangtze craton to the clastic sediments in the Songpan-Ganzi block. The presence of detrital zircon of Neoproterozoic to Triassic ages

  6. Eastern European retailers and wholesalers' buying behaviour

    DEFF Research Database (Denmark)

    Esbjerg, Lars; Stacey, Julia

    1999-01-01

    During the last ten years, retailing in Eastern Europe has undergone considerable changes. The entry of Western European retail chains into Eastern Europe has helped accelerate the distributive trade of Eastern Europe. But what does it take to sell fish and cheese to retailers and wholesalers...... in Eastern Europe compared to Western Europe? Eastern European buyers attach great importance to other aspects when they list new suppliers and products than does Western European retailing. These are the results of a MAPP study of Eastern European retail and wholesale buying behaviour for fish and cheese....... Low prices and favourable terms of payment are most important when retailers in Eastern Europe buy fish and cheese. Then follows the supplier's range of products, trustworthiness of the supplier and product quality. Eastern European wholesalers also rank price and financial conditions as most...

  7. Radioactive mineral potential of carbonatites in western parts of the South American shields

    International Nuclear Information System (INIS)

    Premoli, C.; Kroonenberg, S.B.

    1984-01-01

    During the last eight years at least six carbonatites or clusters of carbonatites have been discovered in the western parts of the South American cratons. In contrast to the carbonatites of the eastern part of the South American shields, which have been well studied and placed in a tectonic context together with the West African carbonatite provinces, those of the western part of the South American cratons have received litte attention. This paper is a compilation of published and original data on these occurrences, their geology, geochemistry, structural setting and radioactive mineral potential. An exploration strategy is devised based on experiences in this rainforest-clad area and the peculiar genetic aspect of carbonatites. Some details of a possibly new uranium mineral encountered in Cerro Cora carbonatite are given. (author)

  8. Intercontinental and intracontinental biogeography of the eastern Asian - Eastern North American disjunct Panax (the ginseng genus, Araliaceae), emphasizing its diversification processes in eastern Asia.

    Science.gov (United States)

    Zuo, Yun-Juan; Wen, Jun; Zhou, Shi-Liang

    2017-12-01

    The intercontinental biogeography between eastern Asia and eastern North America has attracted much attention from evolutionary biologists. Further insights into understanding the evolution of the intercontinental disjunctions have been hampered by the lack of studies on the intracontinental biogeography in eastern Asia, a region with complex geology, geography, climates and habitats. Herein we studied the biogeographic history of the eastern Asian-eastern North American disjunct genus Panax with special emphasis on the investigation of its uneven diversification in Asia. This study reconstructs the diversification history of Panax and also emphasizes a large clade of Panax taxa, which has a wide distribution in eastern Asia, but was unresolved in previous studies. We examined the noncoding plastid DNA fragments of trnH-psbA, rps16, and psbM-trnD, the mitochondrial b/c intron of NAD1, and the nuclear ribosomal internal transcribed spacer (ITS) region of 356 samples from 47 populations. The results revealed the subtropical Northern Hemisphere origin (Asia or Asia and North America) of Panax in the Paleocene. Intercontinental disjunctions between eastern Asia and eastern North America formed twice in Panax, once estimated in early Eocene for the split of P. trifolius and another in mid-Miocene for the divergence of P. quinquefolius. Intercontinental diversifications in Panax showed temporal correlation with the increase of global temperature. The evolutionary radiation of the P. bipinnatifidus species complex occurred around the boundary of Oligocene and Miocene. Strong genetic structure among populations of the species complex was detected and the populations may be isolated by distance. The backbone network and the Bayesian clustering analysis revealed a major evolutionary radiation centered in the Hengduan Mountains of western China. Our results suggested that the evolutionary radiation of Panax was promoted by geographic barriers, including mountain ranges

  9. A historical overview of Moroccan magmatic events along northwest edge of the West African Craton

    Science.gov (United States)

    Ikenne, Moha; Souhassou, Mustapha; Arai, Shoji; Soulaimani, Abderrahmane

    2017-03-01

    Located along the northwestern edge of the West African Craton, Morocco exhibits a wide variety of magmatic events from Archean to Quaternary. The oldest magmatic rocks belong to the Archean Reguibat Shield outcrops in the Moroccan Sahara. Paleoproterozoic magmatism, known as the Anti-Atlas granitoids, is related to the Eburnean orogeny and initial cratonization of the WAC. Mesoproterozoic magmatism is represented by a small number of mafic dykes known henceforth as the Taghdout mafic volcanism. Massive Neoproterozoic magmatic activity, related to the Pan-African cycle, consists of rift-related Tonian magmatism associated with the Rodinia breakup, an Early Cryogenian convergent margin event (760-700 Ma), syn-collisional Bou-Azzer magmatism (680-640 Ma), followed by widespread Ediacaran magmatism (620-555 Ma). Each magmatic episode corresponded to a different geodynamic environment and produced different types of magma. Phanerozoic magmatism began with Early Cambrian basaltic (rift?) volcanism, which persisted during the Middle Cambrian, and into the Early Ordovician. This was succeeded by massive Late Devonian and Carboniferous, pre-Variscan tholeiitic and calc-alkaline (Central Morocco) volcanic flows in basins of the Moroccan Meseta. North of the Atlas Paleozoic Transform Zone, the Late Carboniferous Variscan event was accompanied by the emplacement of 330-300 Ma calc-alkaline granitoids in upper crustal shear zones. Post-Variscan alkaline magmatism was associated with the opening of the Permian basins. Mesozoic magmatism began with the huge volumes of magma emplaced around 200 Ma in the Central Atlantic Magmatic Province (CAMP) which was associated with the fragmentation of Pangea and the subsequent rifting of Central Atlantic. CAMP volcanism occurs in all structural domains of Morocco, from the Anti-Atlas to the External Rif domain with a peak activity around 199 Ma. A second Mesozoic magmatic event is represented by mafic lava flows and gabbroic intrusions in

  10. Apatite fission-track thermochronometric constraints on the exhumation and evolution of the southeastern Indian (Tamil Nadu) passive margin and the role of structural inheritance

    Science.gov (United States)

    De Grave, Johan; Glorie, Stijn; Singh, Tejpal; Van Ranst, Gerben; Nachtergaele, Simon

    2017-04-01

    After rifting from Gondwana in the Late Jurassic - Early Cretaceous, and subsequent opening of the Indian Ocean basin, the continental margins of India developed into typical passive margins. Extensional tectonic forces and thermal subsidence gave rise to the formation of both on-shore and off-shore basins along the southeastern passive margin of the Indian continent, along the Tamil Nadu coast. There, basins such as the Cauvery and Krishna-Godavari basin, accumulated Meso- and Cenozoic (Early Cretaceous to recent) detrital sediments coming off the rifted blocks and the Tamil Nadu hinterland. In places, deep rift basins have accumulated up to over 3000 m of sediments. The continental basement of Tamil Nadu is chiefly composed of metamorphic rocks of the Archean to Palaeoproterozoic Eastern Dharwar Craton and the coeval Southern Granulite Terrane (e.g. Peucat et al., 2013). Several crustal scale shear zones crosscut this assemblage and at least some are considered to represent Gondwanan sutures (Santosh et al., 2012). Smaller, younger granitoid plutons intrude the basement at several locations and most of these are of Late Neoproterozoic age (Glorie et al., 2014). In this work metamorphic basements rocks and the younger granitoids were sampled for a apatite fission-track (AFT) thermochronometric study. A North-South profile from Chennai to Thanjavur mainly transects the Salem block of the Southern Granulite Terrane, and crosscuts several crustal scale shear zones, such as the Cauvery, Salem-Attur and Gangavalli shear zones. Apatites from over 30 samples were used in this study. AFT ages all range between about 190 and 120 Ma (Jurassic - Early Cretaceous). These mainly represent the slow, shallow exhumation of the basement during the rift and early drift phase of the Indian plate from Gondwana. AFT mean track lengths vary between 11 and 13 µm and are typical of slowly exhumed basement. Thermal history modelling (using the QTQt software by Gallagher, 2012) confirms

  11. Surface Wave Analysis of Regional Earthquakes in the Eastern Rift System (Africa)

    Science.gov (United States)

    Oliva, S. J. C.; Guidarelli, M.; Ebinger, C. J.; Roecker, S. W.; Tiberi, C.

    2015-12-01

    The Northern Tanzania Divergence (NTD), the youngest part of the East African Rift System, presents the opportunity to obtain insights about the birth and early stages of rifting before it progresses to mature rifting and seafloor spreading. This region is particularly interesting because the Eastern rift splits into three arms in this area and develops in a region of thick and cold lithosphere, amid the Archaean Tanzanian craton and the Proterozoic orogenic belt (the Masai block). We analyzed about two thousand seismic events recorded by the 39 broadband stations of the CRAFTI network during its two-year deployment in the NTD area in 2013 to 2014. We present the results of surface wave tomographic inversion obtained from fundamental-mode Rayleigh waves for short periods (between 4 to 14 seconds). Group velocity dispersion curves obtained via multiple filter analysis are path-averaged and inverted to produce 0.1º x 0.1º nodal grid tomographic maps for discrete periods using a 2D generalization of the Backus and Gilbert method. To quantify our results in terms of S-wave velocity structure the average group velocity dispersion curves are then inverted, using a linearized least-squares inversion scheme, in order to obtain the shear wave velocity structure for the upper 20 km of the crust. Low velocity anomalies are observed in the region 50 km south of Lake Natron, as well as in the area of the Ngorongoro crater. The implications of our results for the local tectonics and the development of the rifting system will be discussed in light of the growing geophysical database from this region.

  12. Data science implications in diamond formation and craton evolution

    Science.gov (United States)

    Pan, F.; Huang, F.; Fox, P. A.

    2017-12-01

    Diamonds are so-called "messengers" from the deep Earth. Fluid and mineral inclusions in diamonds could reflect the compositions of fluids/melts and wall-rocks in which diamond formed. Recently many diamond samples are examined to study the water content in the mantle transition zone1, the mechanism of diamond formation2 and the mantle evolution history3. However, most of the studies can only explain local activities. Therefore, an overall project of data grouping, comparison and correlation is needed, but limited progress has been made due to a lack of benchmark datasets on diamond formation and effective computing algorithms. In this study, we start by proposing the very first complete and easily-accessible dataset on mineral and fluid inclusions in diamonds. We rescue, collect and organize the data available from papers, journals and other publications resources ([2-4] and more), and then apply several state-of-the-art machine learning methods to tackle this earth science problem by clustering diamond formation process into distinct groups primarily based on the compositions, the formation temperature and pressure, the age and so on. Our ongoing work includes further data exploration and training existing models. Our preliminary results show that diamonds formed from older cratons usually have higher formation temperature. Also peridotitic diamonds take a much larger population than the ecologitic ones. More details are being discovered when we finish constructing the database and training our model. We expect the result to demonstrate the advantages of using machine learning and data science in earth science research problems. Our methodology for knowledge discovery are very general and can be broadly applied to other earth science research problems under the same framework.[1] Pearson et al, Nature (2014); [2] Tomlinson et al, EPSL (2006); [3] Weiss et al, Nature (2016); [4] Stachel and Harris, Ore Geology Reviews (2008); Weiss et al, EPSL (2013)

  13. Assessing health literacy in the eastern and middle-eastern cultures

    OpenAIRE

    Nair, Satish Chandrasekhar; Satish, Karthyayani Priya; Sreedharan, Jayadevan; Ibrahim, Halah

    2016-01-01

    Abstract Background Health literacy is a term employed to assess the ability of people to meet the increasing demands related to health in a rapidly evolving society. Low health literacy can affect the social determinants of health, health outcomes and the use of healthcare services. The purpose of the study was to develop a survey construct to assess health literacy within the context of regional culture. Different socioeconomic status among the Eastern and Middle Eastern countries may restr...

  14. Age and provenance of basement metasediments from the Kubor and Bena Bena Blocks, central Highlands, Papua New Guinea: constraints on the tectonic evolution of the northern Australian cratonic margin

    International Nuclear Information System (INIS)

    Wyck, N.V.; Williams, I.S.

    2002-01-01

    Detrital zircon from two basement blocks (Kubor and Bena Bena) in the central Highlands of Papua New Guinea has an age signature that strongly suggests a northern Australian provenance. Samples of the Omung Metamorphics, southeastern Kubor Block, together yield principal zircon populations with ages of ca 1.8 Ga (∼10 of the total), ca 1.55 Ga (∼10), 470-440 Ma (∼15), ca 340 Ma (∼ 10) and 290-260 Ma (∼40). Two tonalite stocks of the Kubor Intrusive Complex, which intrude the Omung Metamorphics, yield indistinguishable ages of 244.8 ± 4.9 Ma and 239.1 ± 4.2 Ma. Therefore, the deposition and subsequent deformation of the Omung Metamorphics is Late Permian to Early Triassic. A sample of Goroka Formation (Bena Bena Block) contains detrital zircon of similar ages to the Omung Metamorphics, ca 1.8 Ga (5), ca 1.55 Ga (∼45), ca 430 Ma (∼5) and ca 310 Ma (∼40), suggesting that the Goroka Formation has a similar provenance and might be correlative. In contrast, a metapsammite from the Bena Bena Formation yielded only ages of 290-280 Ma (85) and ca 240 Ma (15). A tuff interbedded in the Bena Bena Formation yielded only igneous zircon with a Late Triassic age of 221 ± 3 Ma. Contrary to previous interpretations, the Bena Bena Formation is probably younger than the Goroka Formation. Ages of New Guinea detrital zircon closely match those of igneous and detrital zircon from the Coen Inlier, northeastern Queensland, but contrast with the ages of zircon from terranes further south, east and west. The Kubor and Bena Bena Blocks are not suspect terranes, but rather form part of the Australian craton. The craton margin, modified by rifting during the Mesozoic, was re-inverted during Cenozoic compression. The Australian craton, in the eastern Highlands of Papua New Guinea, extends at least as far north as the Markham Valley, the northern edge of the Bena Bena terrane. All analyses were made on the SHRIMP II sensitive high resolution ion microprobe at the Australian

  15. Geology and geophysics of the Vila Nova Greenstone Belt, northeastern portion of the Amazonian Craton, Amapa, Brazil; Geologia e geofisica do greenstone belt Vila Nova, porcao NE do Craton Amazonico, Amapa, Brasil

    Energy Technology Data Exchange (ETDEWEB)

    Borghetti, Cristiano; Philipp, Ruy Paulo, E-mail: cborghetti@terra.com.br, E-mail: ruy.philipp@ufrgs.br [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre (Brazil)

    2017-01-15

    A few outcrops and strong weathering conditions prevail in the region of the Vila Nova Greenstone Belt in the southeastern Amapa (Brazil). This paper describes the use of airborne geophysical data for geological and structural analysis during geological mapping. This integration aims to improve the geological and tectonic understanding of this portion of the Amazonian Craton. The magnetometric and gamma-spectrometric qualitative interpretation of the images took place in a Geographic Information System (GIS) environment. Recognition of magnetometric and gamma-ray spectrometric units present in the study area was based on the hierarchical classification of polygons outlined by visual interpretation. The major geological domains and the structural patterns were defined by integration of geophysical data, geological mapping and petrographic analysis. The results allowed the recognition of Archean basement rocks composed of orthogneisses and granitoids of the Tumucumaque Complex, the metavolcano-sedimentary rocks of the Vila Nova Complex and Paleoproterozoic granite massifs. The integration of geophysical and field data resulted in the increase of the geological mapping definition, highlighting the importance of this methodology for recognition of complex structural and lithological fabrics in areas of difficult access and scarce fresh rock outcrops. (author)

  16. Lithospheric layering in the North American craton revealed by including Short Period Constraints in Full Waveform Tomography

    Science.gov (United States)

    Roy, C.; Calo, M.; Bodin, T.; Romanowicz, B. A.

    2017-12-01

    Recent receiver function studies of the North American craton suggest the presence of significant layering within the cratonic lithosphere, with significant lateral variations in the depth of the velocity discontinuities. These structural boundaries have been confirmed recently using a transdimensional Markov Chain Monte Carlo approach (TMCMC), inverting surface wave dispersion data and converted phases simultaneously (Calò et al., 2016; Roy and Romanowicz 2017). The lateral resolution of upper mantle structure can be improved with a high density of broadband seismic stations, or with a sparse network using full waveform inversion based on numerical wavefield computation methods such as the Spectral Element Method (SEM). However, inverting for discontinuities with strong topography such as MLDS's or LAB, presents challenges in an inversion framework, both computationally, due to the short periods required, and from the point of view of stability of the inversion. To overcome these limitations, and to improve resolution of layering in the upper mantle, we are developing a methodology that combines full waveform inversion tomography and information provided by short period seismic observables. We have extended the 30 1D radially anisotropic shear velocity profiles of Calò et al. 2016 to several other stations, for which we used a recent shear velocity model (Clouzet et al., 2017) as constraint in the modeling. These 1D profiles, including both isotropic and anisotropic discontinuities in the upper mantle (above 300 km depth) are then used to build a 3D starting model for the full waveform tomographic inversion. This model is built after 1) homogenization of the layered 1D models and 2) interpolation between the 1D smooth profiles and the model of Clouzet et al. 2017, resulting in a smooth 3D starting model. Waveforms used in the inversion are filtered at periods longer than 30s. We use the SEM code "RegSEM" for forward computations and a quasi-Newton inversion

  17. Phylogeography of Eastern Grey Kangaroos, Macropus giganteus, Suggests a Mesic Refugium in Eastern Australia.

    Directory of Open Access Journals (Sweden)

    Brett A Coghlan

    Full Text Available Phylogeographic studies around the world have identified refugia where fauna were able to persist during unsuitable climatic periods, particularly during times of glaciation. In Australia the effects of Pleistocene climate oscillations on rainforest taxa have been well studied but less is known about the effects on mesic-habitat fauna, such as the eastern grey kangaroo (Macropus giganteus. The eastern grey kangaroo is a large mammal that is common and widespread throughout eastern Australia, preferring dry mesic habitat, rather than rainforest. As pollen evidence suggests that the central-eastern part of Australia (southeast Queensland and northern New South Wales experienced cycles of expansion in mesic habitat with contraction in rainforests, and vice versa during glacial and interglacial periods, respectively, we hypothesise that the distribution of the eastern grey kangaroo was affected by these climate oscillations and may have contracted to mesic habitat refugia. From 375 mitochondrial DNA control region sequences from across the distribution of eastern grey kangaroos we obtained 108 unique haplotypes. Phylogenetic analysis identified two clades in Queensland, one of which is newly identified and restricted to a small coastal region in southern Queensland north of Brisbane, known as the Sunshine Coast. The relatively limited geographic range of this genetically isolated clade suggests the possibility of a mesic habitat refugium forming during rainforest expansion during wetter climate cycles. Other potential, although less likely, reasons for the genetic isolation of the highly distinct clade include geographic barriers, separate northward expansions, and strong local adaptation.

  18. Phylogeography of Eastern Grey Kangaroos, Macropus giganteus, Suggests a Mesic Refugium in Eastern Australia.

    Science.gov (United States)

    Coghlan, Brett A; Goldizen, Anne W; Thomson, Vicki A; Seddon, Jennifer M

    2015-01-01

    Phylogeographic studies around the world have identified refugia where fauna were able to persist during unsuitable climatic periods, particularly during times of glaciation. In Australia the effects of Pleistocene climate oscillations on rainforest taxa have been well studied but less is known about the effects on mesic-habitat fauna, such as the eastern grey kangaroo (Macropus giganteus). The eastern grey kangaroo is a large mammal that is common and widespread throughout eastern Australia, preferring dry mesic habitat, rather than rainforest. As pollen evidence suggests that the central-eastern part of Australia (southeast Queensland and northern New South Wales) experienced cycles of expansion in mesic habitat with contraction in rainforests, and vice versa during glacial and interglacial periods, respectively, we hypothesise that the distribution of the eastern grey kangaroo was affected by these climate oscillations and may have contracted to mesic habitat refugia. From 375 mitochondrial DNA control region sequences from across the distribution of eastern grey kangaroos we obtained 108 unique haplotypes. Phylogenetic analysis identified two clades in Queensland, one of which is newly identified and restricted to a small coastal region in southern Queensland north of Brisbane, known as the Sunshine Coast. The relatively limited geographic range of this genetically isolated clade suggests the possibility of a mesic habitat refugium forming during rainforest expansion during wetter climate cycles. Other potential, although less likely, reasons for the genetic isolation of the highly distinct clade include geographic barriers, separate northward expansions, and strong local adaptation.

  19. Isotopic characteristics (Nd and Sr) of the intrusive plutonism at the northwestern Amazonian Craton, Venezuela, and implications for the Paleoproterozoic evolution

    International Nuclear Information System (INIS)

    Teixeira, Wilson; Tassinari, Colombro Celso G.; Mondin, M.

    2002-01-01

    Nd and Sr analyses were performed on selected granitoid plutons that intrude Archean and Paleoproterozoic domains of the Guyana shield (Venezuela). The isotopic signatures of these plutons together with the geochronologic background of the country rocks are used to constrain their magma genesis and tectonic setting within the Paleoproterozoic evolutions of mobile belts (Maroni-Itacaiunas and Ventuari-Tapajos provinces) of the Amazonian Craton. The Encrucijada Suite (2187 +- 94 Ma), which intrudes Archean rocks of the Imataca Complex, originated predominantly from partial melt of this crust, as supported by negative epsilon Nd(2.1Ga ) values (-2.2 to - 4.9) and T DM ages between 2.82 and 2.49 Ga. Conversely, the plutons from the Supamo Complex (2230 - 2050 Ma) and Cuchivero Group (1980 - 1830 Ma), occurring within the adjoining Paleoproterozoic provinces, are juvenile in nature (derived from roughly contemporary protoliths). These bodies display T DM ages between 2.13 and 2.22 Ga, as well as positive epsilon Nd(2.1Ga ) values (+0.74 to + 3.05). Isotopic correlation diagrams 143 Nd/144 Nd vs. 147 Sm/144 Nd and 143 Nd/144 Nd vs. time) plotted together with the plutonic rocks and Imataca Complex rocks were evaluated taking into account the geologic background of the NW part of the Amazonian Craton. Interpretation of these isotopic data supports the idea of tectonic juxtaposition between the Imataca Complex and the Maroni-Itacaiunas province during the Transamazonian orogeny (2.25 - 2.05 Ga). On the other hand, the Cuchivero Group plutons have a contrasting isotopic signature compared to the other Paleoproterozoic plutonic rocks. This is consistent with the existence of a tectonic boundary between the Maroni-Itacaiunas and the Ventuari-Tapajos province in the late Paleoproterozoic. (author)

  20. Granitoids of the Dry Valleys area, southern Victoria Land : geochemistry and evolution along the early Paleozoic Antarctic Craton margin

    International Nuclear Information System (INIS)

    Allibone, A.H.; Cox, S.C.; Smillie, R.W.

    1993-01-01

    Field relationships and geochemistry indicate granitoid plutons of the Dry Valleys area comprise at least three petrogenetically distinct suites. The older Dry Valleys 1a (DV1a) suite, comprising the Bonney, Catspaw, Denton, Cavendish, and Wheeler Plutons and hornblende-biotite orthogneisses, and Dry Valleys 1b (DV1b) suite, comprising the Hedley, Valhalla, St Johns, Dun, Calkin, and Suess Plutons, biotite granitoid dikes and biotite orthogneisses, were emplaced before prominent swarms of Vanda mafic and felsic dikes. Both the DV1a and DV1b suites are time transgressive, with older intrusions in each suite being emplaced during the later stages of deformation of the Koettlitz Group. Younger granitoids that postdate the majority of the Vanda dikes include: the Dry Valleys 2 (DV2) suite, comprising the Pearse and Nibelungen Plutons plus several smaller, unnamed plugs; and the Harker, Swinford, Orestes, and Brownworth Plutons with identical field relationships and enclaves but distinct chemistries. Chemical characteristics and limited Rb-Sr isotopic dating indicate plutonism before c. 500 Ma was dominated by the Cordilleran I-type DV1a suite, inferred to have developed during melting above a west-dipping subduction zone along the Antarctic Craton margin. The chemical characteristics of the DV1b suite indicate large-scale melting of a quartzo-feldspathic protolith lacking residual plagioclase, but containing refractory garnet. Potential DV1b suite source rocks include metamorphosed immature sediments, possibly underplated along the subduction zone associated with DV1a magmatism, or older granitoid orthogneisses. Major DV1b plutonism at 490 Ma marks the end of subduction-related plutonism in southern Victoria Land. Younger DV2 alkali-calcic, Caledonian I-type plutonism is inferred to have formed in response to uplift and extension between 480 and 455 Ma. Lack of DV2 suite correlatives and Vanda mafic and felsic dikes in northern Victoria Land suggests significantly

  1. Lu-Hf isotope constraints on plume-lithosphere interaction during emplacement of the Bushveld Large Igneous Province at 2.06 Ga: Implications for the structure and evolution of the Kaapvaal Craton's lithospheric mantle

    Science.gov (United States)

    Zirakparvar, N. A.; Mathez, E. A.; Rajesh, H.; Vervoort, J. D.; Choe, S.

    2016-12-01

    The Bushveld Large Igneous Province (B-LIP) comprises a diverse array of >30 magma bodies that intruded the Kaapvaal Craton at 2.06 Ga. In this talk we use zircon and bulk-rock Lu-Hf isotope data to show that the B-LIP formed in response to the arrival of a plume(s) from the deep mantle. New zircon Hf isotope compositions for four B-LIP bodies yield intrusion-specific average ɛHf (2.06 Ga) values that range from -20.7 ± 2.8 to -2.7 ± 2.8, largely consistent with literature zircon data for other B-LIP intrusions. Bulk-rock solution ɛHf (2.06 Ga) values for a variety of B-LIP intrusions range from -2.1 ± 0.2 to -10.6 ± 0.2. Because the most radiogenic Hf isotope compositions across the entire B-LIP are nearly primordial with an ɛHf (2.06 Ga) close to 0, it is likely that the heat source of the B-LIP was a plume(s) from deep mantle. The Hf isotope data further suggests that individual intrusions in the B-LIP can be grouped into four categories based on their ultimate sources: 1) melts generated in subduction and plume modified continental lithospheric mantle; 2) melts generated by melting of a mafic-ultramafic reservoir composed of older ( 2.7 Ga) plume-related material trapped in the Kaapvaal lithosphere; 3) melts generated in the mid- to upper crust; and 4) melts generated from the 2.06 Ga mantle plume itself. The presence of 2.7 Ga mafic-ultramafic material in the Kaapvaal lithosphere may have acted to strengthen the lithosphere so that it was able to resist being dispered by the arrival of the B-LIP plume at 2.06 Ga. Because the B-LIP extends into a 2.7 Ga aged suture zone between the Kaapvaal and Zimbabwe cratons, it is also possible to understand the role of the lithospheric mantle in producing the Lu-Hf signatures observed in the various B-LIP intrusions as a function of two different types of the continental lithosphere: The very old lithosphere comprising the Kaapvaal Craton and the somewhat younger lithosphere comprising the suture zone. A basic

  2. Environmental protection in Eastern Europe

    International Nuclear Information System (INIS)

    Kabala, S.

    1990-01-01

    There is a need for the development of institutional structures to make the transfer of technology work to improve the ability of Eastern Europe to find solutions to its environmental problems. Envisioned is technical assistance: U.S. experts who will work on-site with Eastern European experts. The idea is to technically train individuals in pollution-prevention methods. Trained experts could then upgrade processes to save input, energy, and materials. In the exchange of environmental information, discussions have led to four issues: it is expensive to transfer equipment and make qualified personnel available for a long period; information is comparatively inexpensive to convey; in Eastern Europe there are trained and competent personnel; the theoretical knowledge, academic knowledge, and education are at a very high level but little of this knowledge has been put into practice. The technology transfer goal is to develop a response to needs identified by partner institutions and counterpart professionals that will enable Eastern Europe to tap resources that do exist- scientific, managerial, and economic resources and tap information resources in the US in order to address the environmental problems that exist in Eastern Europe

  3. Lithospheric thermal-rheological structure of the Ordos Basin and its geodynamics

    Science.gov (United States)

    Pan, J.; Huang, F.; He, L.; Wu, Q.

    2015-12-01

    The study on the destruction of the North China Craton has always been one of the hottest issues in earth sciences.Both mechanism and spatial variation are debated fiercely, still unclear.However, geothermal research on the subject is relatively few. Ordos Basin, located in the west of the North China Craton, is a typical intraplate. Based on two-dimensional thermal modeling along a profile across Ordos Basin from east to west, obtained the lithospheric thermal structure and rheology. Mantle heat flow in different regions of Ordos Basin is from 21.2 to 24.5 mW/m2. In the east mantle heat flow is higher while heat flow in western region is relatively low. But mantle heat flow is smooth and low overall, showing a stable thermal background. Ratio of crustal and mantle heat flow is between 1.51 and 1.84, indicating that thermal contribution from shallow crust is lower than that from the mantle. Rheological characteristics along the profile are almost showed as "jelly sandwich" model and stable continental lithosphere structure,which is represent by a weak crust portion but a strong lithospheric mantle portion in vertical strength profile. Based on above , both thermal structure and lithospheric rheology of Ordos Basin illustrate that tectonic dynamics environment in the west of North China Craton is relatively stable. By the study on lithospheric thermal structure, we focus on the disparity in thickness between the thermal lithosphere and seismic lithosphere.The difference in western Ordos Basin is about 140km, which decreases gradually from Fenwei graben in the eastern Ordos Basin to the Bohai Bay Basin.That is to say the difference decreases gradually from the west to the east of North China Craton.The simulation results imply that viscosity of the asthenosphere under North China Craton also decreases gradually from west to east, confirming that dehydration of the Pacific subduction is likely to have great effect on the North China Craton.

  4. Geochronological and sedimentological evidences of Panyangshan foreland basin for tectonic control on the Late Paleozoic plate marginal orogenic belt along the northern margin of the North China Craton

    Science.gov (United States)

    Li, Jialiang; Zhou, Zhiguang; He, Yingfu; Wang, Guosheng; Wu, Chen; Liu, Changfeng; Yao, Guang; Xu, Wentao; Zhao, Xiaoqi; Dai, Pengfei

    2017-08-01

    There is a wide support that the Inner Mongolia Palaeo-uplift on the northern margin of the North China Craton has undergone an uplifting history. However, when and how did the uplift occurred keeps controversial. Extensive field-based structural, metamorphic, geochemical, geochronological and geophysical investigations on the Inner Mongolia Palaeo-uplift, which suggested that the Inner Mongolia Palaeo-uplift was an uplifted region since the Early Precambrian or range from Late Carboniferous-Early Jurassic. The geochemical characteristics of the Late Paleozoic to Early Mesozoic intrusive rocks indicated that the Inner Mongolia Palaeo-uplift was an Andean-type continental margin that is the extensional tectonic setting. To address the spatial and temporal development of the Inner Mongolia Palaeo-uplift, we have carried out provenance analysis of Permian sedimentary rocks which collected from the Panyangshan basin along the northern margin of the North China Craton. The QFL diagram revealed a dissected arc-recycled orogenic tectonic setting. Moreover, the framework grains are abundant with feldspar (36-50%), indicating the short transport distance and unstable tectonic setting. Detrital zircon U-Pb analysis ascertained possible provenance information: the Precambrian basement ( 2490 and 1840 Ma) and continental arc magmatic action ( 279 and 295 Ma) along the northern margin of the North China Craton. The projection in rose diagrams of the mean palaeocurrent direction, revealing the SSW and SSE palaeoflow direction, also shows the provenance of the Panyangshan basin sources mainly from the Inner Mongolia Palaeo-uplift. The andesite overlying the Naobaogou Formation has yielded U-Pb age of 277.3 ± 1.4 Ma. The additional dioritic porphyry dike intruded the Naobaogou and Laowopu Formations, which has an emplacement age of 236 ± 1 Ma. The above data identify that the basin formed ranges from Early Permian to Middle Triassic (277-236 Ma). Accordingly, the Inner Mongolia

  5. Origin and tectonic evolution of early Paleozoic arc terranes abutting the northern margin of North China Craton

    Science.gov (United States)

    Zhou, Hao; Pei, Fu-Ping; Zhang, Ying; Zhou, Zhong-Biao; Xu, Wen-Liang; Wang, Zhi-Wei; Cao, Hua-Hua; Yang, Chuan

    2017-12-01

    The origin and tectonic evolution of the early Paleozoic arc terranes abutting the northern margin of the North China Craton (NCC) are widely debated. This paper presents detrital zircon U-Pb and Hf isotopic data of early Paleozoic strata in the Zhangjiatun arc terrane of central Jilin Province, northeast (NE) China, and compares them with the Bainaimiao and Jiangyu arc terranes abutting the northern margin of the NCC. Detrital zircons from early Paleozoic strata in three arc terranes exhibit comparable age groupings of 539-430, 1250-577, and 2800-1600 Ma. The Paleoproterozoic to Neoarchean ages and Hf isotopic composition of the detrital zircons imply the existence of the Precambrian fragments beneath the arc terranes. Given the evidences from geology, igneous rocks, and detrital zircons, we proposed that the early Paleozoic arc terranes abutting the northern margin of the NCC are a united arc terrane including the exotic Precambrian fragments, and these fragments shared a common evolutionary history from Neoproterozoic to early-middle Paleozoic.

  6. Comparison of mantle lithosphere beneath early Triassic kimberlite fields in Siberian craton reconstructed from deep-seated xenocrysts

    Directory of Open Access Journals (Sweden)

    I.V. Ashchepkov

    2016-07-01

    Kharamai mantle clinopyroxenes represent three geochemical types: (1 harzburgitic with inclined linear REE, HFSE troughs and elevated Th, U; (2 lherzolitic or pyroxenitic with round TRE patterns and decreasing incompatible elements; (3 eclogitic with Eu troughs, Pb peak and high LILE content. Calculated parental melts for garnets with humped REE patterns suggest dissolution of former Cpx and depression means Cpx and garnets extraction. Clinopyroxenes from Ary-Mastakh fields show less inclined REE patterns with HMREE troughs and an increase of incompatible elements. Clinopyroxenes from Kuranakh field show flatter spoon-like REE patterns and peaks in Ba, U, Pb and Sr, similar to those in ophiolitic harzburgites. The PT diagrams for the mantle sections show high temperature gradients in the uppermost SCLM accompanied by an increase of P-Fe#Ol upward and slightly reduced thickness of the mantle keel of the Siberian craton, resulting from the influence of the Permian–Triassic superplume, but with no signs of delamination.

  7. Gas in Eastern Europe

    International Nuclear Information System (INIS)

    Anon.

    1994-01-01

    West European gas companies have long recognised the potential for lucrative business within eastern Europe. But they recognise that the region's integration into the west European system will be far from straightforward, with deals between east European gas companies and their western counterparts invariably containing financial mechanisms, such as barter trade, that are designed to cope with the easterners' shortage of hard currency. (author)

  8. SHRIMP zircon dating and LA-ICPMS Hf analysis of early Precambrian rocks from drill holes into the basement beneath the Central Hebei Basin, North China Craton

    Directory of Open Access Journals (Sweden)

    Yusheng Wan

    2014-07-01

    Full Text Available The Central Hebei Basin (CHB is one of the largest sedimentary basins in the North China Craton, extending in a northeast–southwest direction with an area of >350 km2. We carried out SHRIMP zircon dating, Hf-in-zircon isotopic analysis and a whole-rock geochemical study on igneous and metasedimentary rocks recovered from drill holes that penetrated into the basement of the CHB. Two samples of gneissic granodiorite (XG1-1 and gneissic quartz diorite (J48-1 have magmatic ages of 2500 and 2496 Ma, respectively. Their zircons also record metamorphic ages of 2.41–2.51 and ∼2.5 Ga, respectively. Compared with the gneissic granodiorite, the gneissic quartz diorite has higher ΣREE contents and lower Eu/Eu* and (La/Ybn values. Two metasedimentary samples (MG1, H5 mainly contain ∼2.5 Ga detrital zircons as well as late Paleoproterozoic metamorphic grains. The zircons of different origins have εHf (2.5 Ga values and Hf crustal model ages ranging from 0 to 5 and 2.7 to 2.9 Ga, respectively. Therefore, ∼2.5 Ga magmatic and Paleoproterozoic metasedimentary rocks and late Neoarchean to early Paleoproterozoic and late Paleoproterozoic tectono-thermal events have been identified in the basement beneath the CHB. Based on regional comparisons, we conclude that the early Precambrian basement beneath the CHB is part of the North China Craton.

  9. Eastern Sources of Invitational Education.

    Science.gov (United States)

    Ryback, David

    1993-01-01

    Presents historical perspective suggesting that invitational theory shares many beliefs with ancient Eastern philosophies. Submits that teachers and other educators who embrace the invitational perspective may benefit from an understanding of Eastern principles. Briefly describes Buddhism, Confucianism, Taoism, Zen Buddhism, and their relevance to…

  10. Prevalence of blood parasites in eastern versus Western house finches: are eastern birds resistant to infection?

    Science.gov (United States)

    Davis, Andrew K; Hood, Wendy R; Hill, Geoffrey E

    2013-09-01

    The rapid spread of the bacterial disease, Mycoplasma gallisepticum (MG), throughout the introduced range of house finches (Carpodacus mexicanus) in eastern North America, compared to its slower spread through the native western range, has puzzled researchers and highlights the need to understand the relative differences in health state of finches from both populations. We conducted a light-microscope survey of hemoparasites in populations of finches from Arizona (within the western range) and from Alabama (within the eastern range), and compared our estimates of prevalence to published reports from house finches sampled in both ranges. Of the 33 Arizona birds examined, we recorded hematozoan infections in 16 (48.5%) individuals, compared to 1 infected Alabama bird out of 30 birds examined (3.3%). Based on independent surveys of seven western North American and five eastern North American populations of house finches the average prevalence of blood parasites in western populations is 38.8% (±17.9 SD), while the average prevalence within the eastern range is only 5.9% (±6.1 SD). The average rate of infection among all songbirds sampled in the east is 34.2% (±4.8 SD). Thus, our surveys of wild birds as well as previously published observations point to eastern house finches having a much lower prevalence of blood parasite infections than their western counterparts. Combined with the fact that eastern finches also tend to have lower rates of avian pox infections than do western birds (based on a literature review), these observations suggest that eastern birds have either strong resistance to these infections or high susceptibility and associated mortality.

  11. Rift propagation at craton margin.: Distribution of faulting and volcanism in the North Tanzanian Divergence (East Africa) during Neogene times

    Science.gov (United States)

    Le Gall, B.; Nonnotte, P.; Rolet, J.; Benoit, M.; Guillou, H.; Mousseau-Nonnotte, M.; Albaric, J.; Deverchère, J.

    2008-02-01

    A revised kinematic model is proposed for the Neogene tectono-magmatic development of the North Tanzanian Divergence where the axial valley in S Kenya splits southwards into a wide diverging pattern of block faulting in association with the disappearance of volcanism. Propagation of rifting along the S Kenya proto-rift during the last 8 Ma is first assumed to have operated by linkage of discrete magmatic cells as far S as the Ngorongoro-Kilimanjaro transverse volcanic belt that follows the margin of cratonic blocks in N Tanzania. Strain is believed to have nucleated throughout the thermally-weakened lithosphere in the transverse volcanic belt that might have later linked the S Kenya and N Tanzania rift segments with marked structural changes along-strike. The North Tanzanian Divergence is now regarded as a two-armed rift pattern involving: (1) a wide domain of tilted fault blocks to the W (Mbulu) that encompasses the Eyasi and Manyara fault systems, in direct continuation with the Natron northern trough. The reactivation of basement fabrics in the cold and intact Precambrian lithosphere in the Mbulu domain resulted in an oblique rift pattern that contrasts with the orthogonal extension that prevailed in the Magadi-Natron trough above a more attenuated lithosphere. (2) To the E, the Pangani horst-like range is thought to be a younger (< 1 Ma) structure that formed in response to the relocation of extension S of the Kilimanjaro magmatic center. A significant contrast in the mechanical behaviour of the stretched lithosphere in the North Tanzanian diverging rift is assumed to have occurred on both sides of the Masai cratonic block with a mid-crustal decoupling level to the W where asymmetrical fault-basin patterns are dominant (Magadi-Natron and Mbulu), whereas a component of dynamical uplift is suspected to have caused the topographic elevation of the Pangani range in relation with possible far-travelled mantle melts produced at depth further N.

  12. Russian aeromagnetic surveys of the Prince Charles Mountains and adjacent regions into the 21st century

    Science.gov (United States)

    Golynsky, Alexander; Golynsky, Dmitry; Kiselev, Alexander; Masolov, Valery

    2014-05-01

    Russian aeromagnetic investigations in the Prince Charles Mountains (PCM) and surrounding areas, seek to contribute data on the tectonics of Precambrian igneous belts and cratonic fragments, the crustal structure of the Lambert Rift system and other major aspects of Antarctic geology, critical to understanding continental growth processes (Golynsky et al., 2006). Over the past decade, the Polar Marine Geoscience Expedition projects acquired approximately 77,400 line-km of aeromagnetic data over the largely ice-covered regions of MacRobertson Land and Princess Elizabeth Land. The airborne surveys were performed with a standard profile spacing of 5 km and tie-line interval of 15-25 km. The total amount of the Russian aeromagnetic data collected in this region exceeded more than 165,000 line-km. Together with the PCMEGA and AGAP surveys (Damaske and McLean, 2005; Ferraccioli et al., 2011) the PMGE dataset forms the longest transect ever mapped in East Antarctica exceeding 1950 km in length. Several distinct crustal subdivisions are clearly differentiated in the magnetic data. The high-amplitude positive anomalies that extend around the Vestfold Hills and Rauer Islands are likely be attributed to the southern boundary of high-grade metamorphic Late Archean craton. The northern PCM that are composed by ~1 Ga orthogneiss and charnockite display a predominantly northeasterly trending magnetic fabric that continues to the eastern shoulder of the Lambert Rift. The aeromagnetic data from the Southern PCM reveal the spatial boundary of the Archaean Ruker Terrane that is characterized by a short-wavelength anomalies and the prominent Ruker Anomaly that is associated with a banded iron formation. The prominent alternating system of linear NE-SW positive and negative anomalies over the eastern shoulder of the Lambert Rift may reflect the western boundary of the Princess Elizabeth Land cratonic(?) block, although its relationships and tectonic origin remained largely ambiguous

  13. Regional Development of Eastern Slovakia

    Directory of Open Access Journals (Sweden)

    Monika Hergezelová

    2017-08-01

    Full Text Available Purpose and Originality: The aim of the work is to provide an overview of regional development in Eastern Slovakia, where are Košice and Prešov Region. The originality of the work lies in the work of enriching the SWOT analysis from the author Eve Rajčáková, which is given in the book deals with the issue of Regional development and regional policy of the European Union and Slovakia. Research question: The conditions of life of people in eastern Slovakia. Method: For writing this contribution will be used method of analysis and statistics. Knowledge on this subject have been looking on the internet and in books and sources of information publicly available. Using the data collected, we dealt with the issue of regional development in the Košice and Prešov regions. Results: The topic was the beginning focused on the overall characteristics of eastern Slovakia. Furthermore, we are at work we dealt with social and economic phenomena in both regions of eastern Slovakia. We focused on GDP, unemployment and tourism, which is in the region is widespread. Society: It is well known that there are obviously different living conditions in eastern Slovakia as in other parts of Slovakia. People are forced to, mainly because of employment, leave their region to move or commute to work to the west. The paper point out the right of this negative phenomenon that is quite visible - high unemployment. Limitations: The limits of work are limited by problems of regional development in eastern Slovakia, mainly focusing on economic and social phenomena in the society.

  14. Diamond ages from Victor (Superior Craton): Intra-mantle cycling of volatiles (C, N, S) during supercontinent reorganisation

    Science.gov (United States)

    Aulbach, S.; Creaser, Robert A.; Stachel, Thomas; Heaman, Larry M.; Chinn, Ingrid L.; Kong, Julie

    2018-05-01

    The central Superior Craton hosts both the diamondiferous 1.1 Ga Kyle Lake and Jurassic Attawapiskat kimberlites. A major thermal event related to the Midcontinent Rift at ca. 1.1 Ga induced an elevated geothermal gradient that largely destroyed an older generation of diamonds, raising the question of when, and how, the diamond inventory beneath Attawapiskat was formed. We determined Re-Os isotope systematics of sulphides included in diamonds from Victor by isotope dilution negative thermal ionisation mass spectrometry in order to obtain insights into the age and nature of the diamond source in the context of regional tectonothermal evolution. Regression of the peridotitic inclusion data (n = 14 of 16) yields a 718 ± 49 Ma age, with an initial 187Os/188Os ratio of 0.1177 ± 0.0016, i.e. depleted at the time of formation (γOs -3.7 ± 1.3). Consequently, Re depletion model ages calculated for these samples are systematically overestimated. Given that reported 187Os/188Os in olivine from Attawapiskat xenoliths varies strongly (0.1012-0.1821), the low and nearly identical initial Os of sulphide inclusions combined with their high 187Re/188Os (median 0.34) suggest metasomatic formation from a mixed source. This was likely facilitated by percolation of amounts of melt sufficient to homogenise Os, (re)crystallise sulphide and (co)precipitate diamond; that is, the sulphide inclusions and their diamond host are synchronous if not syngenetic. The ∼720 Ma age corresponds to rifting beyond the northern craton margin during Rodinia break-up. This suggests mobilisation of volatiles (C, N, S) and Os due to attendant mantle stretching and metasomatism by initially oxidising and S-undersaturated melts, which ultimately produced lherzolitic diamonds with high N contents compared to older Kyle Lake diamonds. Thus, some rift-influenced settings are prospective with respect to diamond formation. They are also important sites of hidden, intra-lithospheric volatile redistribution

  15. The Eastern Partnership

    DEFF Research Database (Denmark)

    Nielsen, Kristian L.; Vilson, Maili

    2014-01-01

    When the EU launched the Eastern Partnership (EaP) in 2009, it did so with much rhetoric about projecting its soft power into Eastern Europe. Yet today, the EU's soft power project seems to have stalled, with developments in the region being less than favourable. This article argues that the EaP...... essentially replicated the main weaknesses of the European Neighbourhood Policy, by offering too little incentive and support to the partners, rendering both conditionality and soft power ineffective as tools for milieu shaping. In promoting the EaP as a policy of soft power, the EU has once again forgotten...

  16. The White Nile as a source for Nile sediments: Assessment using U-Pb geochronology of detrital rutile and monazite

    Science.gov (United States)

    Be'eri-Shlevin, Yaron; Avigad, Dov; Gerdes, Axel

    2018-04-01

    Basement terranes exposed at the headwaters of the White Nile include Archean-Paleoproterozoic rocks of the Congo Craton, whose northern sectors were severely reworked during Neoproterozoic orogeny. New U-Pb analyses of detrital rutile and monazite from early Quaternary to Recent coastal quartz sands of Israel, at the northeast extension of the Nile sedimentary system, yield mostly late Neoproterozoic ages, with a dominant peak at ca. 600 Ma. While derivation from the reworked sectors of the Craton cannot be negated, the absence of pre-Neoproterozoic rutile and monazite indicates that the detrital contribution from the Congo cratonic nuclei into the main Nile was insignificant. The near absence of White Nile basement-derived heavy minerals from the Nile sands arriving at the Eastern Mediterranean may be explained by a number of factors such as relatively minor erosion of the Cratonic basement nuclei during the Quaternary, late connection of the White Nile to the main Nile system with a possibility that northern segments connected prior to more southerly ones, and a long-term effective sediment blockage mechanism at the mouth of White Nile. Likewise, our previous study demonstrated that Nile sands display a detrital zircon U-Pb-Hf pattern consistent with significant recycling of NE African Paleozoic sediments. It is thus plausible that any detrital contribution from White Nile basement rocks was thoroughly diluted by eroded Paleozoic sediments, or their recycled products, which were likely the greatest sand reservoir in the region. This study adds to previous studies showing the advantage of a multi mineral U-Pb geochronology strategy in constraining sediment provenance patterns.

  17. Rb-Sr geochronology and geochemical characteristics of mafic dikes in the Nova Lacerda and Conquista D'Oeste region, Mato Grosso, SW Amazonian Craton; Geocronologia Rb-Sr e caracteristicas geoquimicas dos diques maficos da regiao de Nova Lacerda e Conquista D'Oeste (MT), porcao sudoeste do Craton Amazonico

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Paulo Cesar Correa da; Matos, Joao Batista de [Universidade Federal de Mato Grosso (UFMT), Cuiaba, MT (Brazil). Dept. de Recursos Minerais; Grupo de Pesquisas em Evolucao Crustal e Metalogenia Guapore, Cuiaba, MT (Brazil)], e-mail: pccorrea@ufmt.br, e-mail: jmatos@cpd.ufmt.br; Girardi, Vicente Antonio Vitorio [Universidade de Sao Paulo (USP), SP (Brazil). Inst. de Geociencias. Dept. de Mineralogia e Geotectonica], e-mail: girardi@usp.br; Ruiz, Amarildo Salina [Universidade Federal de Mato Grosso (UFMT), Cuiaba, MT (Brazil). Dept. de Geologia Geral; Grupo de Pesquisas em Evolucao Crustal e Metalogenia Guapore, Cuiaba, MT (Brazil)], e-mail: asruiz@rc.unesp.br

    2009-07-01

    In the Nova Lacerda and Conquista D'Oeste regions, Mato Grosso State, SW part of the Amazonian Craton, mafic dikes trending NNW intrude the Nova Lacerda Granite (1462{+-}12 Ma), within the Jauru Domain, in the Rondonia-San Ignacio Province (1.55 - 1.3 Ga). The mafic swarm comprises diabases, metadiabases and amphibolites. Metadiabases originated from uralitization of diabases. These rocks have tholeiitic affinity and predominant basaltic composition. Some samples are andesi-basalts. The ages of diabases and metabasites are 1380 {+-} 32 Ma and 1330 {+-} 120 Ma respectively. Geochemical data indicate that the compositional variation of diabases and metadiadases is due to fractional crystallization of evolved tholeiitic magmas. The origin of the basaltic magmas is related to a heterogeneous mantle source. (author)

  18. Recognized Multiple Rifts of the Neoproterozoic in the Initiation of the Tarim Craton (NW China) and Their Tectonic Implications

    Science.gov (United States)

    He, B.; Jiao, C.; Huang, T.; Zhou, X.; Cai, Z.; Cao, Z.; Jiang, Z.; Cui, J.; Yu, Z.; Chen, W.

    2017-12-01

    The Tarim Basin is the largest, oil-bearing and superimposed basin in the northwest of China. The development and tectonic property of the initial Tarim basin have been acutely disputed and remain enigmatic. Urgently need to reveal the origin and formation dynamics of the Tarim Carton and evaluate the potential of the deep energy resources. However, covered by vast desert and huge-thickness sedimentary strata, suffered by multiple tectonic movements, seismic data with low signal- to- noise ratio in the deep are the critical difficulties. We analyse 4 field outcrops, 18 wells, 27 reprocessed seismic reflection profiles with high SNR across the basin and many ancillary ones and aeromagnetic data. We find about 20 normal fault-controlled rift depressions of the Cryogenian and Ediacaran scattered in the Tarim basin, which developed on the Precambrian metamorphic and crystalline basements and covered by the epeiric sea and basin facies sediments of the Lower Cambrian. The structural styles of the rifts are mainly half grabens, symmetrical troughs and horst-grabens. The regional differences exist obviously in spatial and temporal. The WNW-ESE-trending faults occur in the central part and northern of the basin and the NE, and the NEE-trending faults occur in the southern parts, which response with the anomaly of aeromagnetic. Some main faults of the Ediacaran inherited from the Cryogenian and some occurred newly, the more rifting depressions occurred during the Ediacaran. The extensional NNW-SSE-oriented and NNE-SSW-oriented paleostress field occurred simultaneously during rifting, and accompanied with the clockwise shearing. According to the activities of syn-sedimentary faults, magmatic events and sediments, the tectonic properties of the rifts are different depending on their locations in the Tarim craton. The rifting phases mainly occurred from 780 Ma to 615 Ma. The formation of rifts were associated with the opening of the South Tianshan Ocean and the South Altun

  19. Regional and temporal variability of melts during a Cordilleran magma pulse: Age and chemical evolution of the jurassic arc, eastern mojave desert, California

    Science.gov (United States)

    Barth, A.P.; Wooden, J.L.; Miller, David; Howard, Keith A.; Fox, Lydia; Schermer, Elizabeth R.; Jacobson, C.E.

    2017-01-01

    Intrusive rock sequences in the central and eastern Mojave Desert segment of the Jurassic Cordilleran arc of the western United States record regional and temporal variations in magmas generated during the second prominent pulse of Mesozoic continental arc magmatism. U/Pb zircon ages provide temporal control for describing variations in rock and zircon geochemistry that reflect differences in magma source components. These source signatures are discernible through mixing and fractionation processes associated with magma ascent and emplacement. The oldest well-dated Jurassic rocks defining initiation of the Jurassic pulse are a 183 Ma monzodiorite and a 181 Ma ignimbrite. Early to Middle Jurassic intrusive rocks comprising the main stage of magmatism include two high-K calc-alkalic groups: to the north, the deformed 183–172 Ma Fort Irwin sequence and contemporaneous rocks in the Granite and Clipper Mountains, and to the south, the 167–164 Ma Bullion sequence. A Late Jurassic suite of shoshonitic, alkali-calcic intrusive rocks, the Bristol Mountains sequence, ranges in age from 164 to 161 Ma and was emplaced as the pulse began to wane. Whole-rock and zircon trace-element geochemistry defines a compositionally coherent Jurassic arc with regional and secular variations in melt compositions. The arc evolved through the magma pulse by progressively greater input of old cratonic crust and lithospheric mantle into the arc magma system, synchronous with progressive regional crustal thickening.

  20. Lithosphere density structure beneath the eastern margin of the Tibetan Plateau and its surrounding areas derived from GOCE gradients data

    Directory of Open Access Journals (Sweden)

    Honglei Li

    2017-05-01

    Full Text Available A three-dimensional density model of the crust and uppermost mantle is determined by the inversion of a set of GOCE gravity and gradients residual anomalies beneath the eastern margin of the Tibetan Plateau and its surrounding areas. In our work, we choose five independent gravity gradients (Txx, Tzz, Txy, Txz, Tyz to perform density inversion. Objective function is given based on Tikhonov regularization theory. Seismic S-wave velocities play the role of initial constraint for the inversion based on a relationship between density and S-wave velocity. Damped Least Square method is used during the inversion. The final density results offer some insights into understanding the underlying geodynamic processes: (1 Low densities in the margin of the Tibet, along with low wave velocity and resistivity results, yield conversions from soft and weak Tibet to the hard and rigid cratons. (2The lowest densities are found in the boundary of the plateau, instead of the whole Tibet indicates that the effects of extrusion stress environment in the margin affect the changes of the substance there. The substances and environments conditioning for the earthquake preparations and strong deformation in this transitional zone. (3 Evident low-D anomaly in the upper and middle crust in the Lasha terrane and Songpan-Ganzi terrane illustrated the eastward sub-ducted of southeastern Tibet, which could be accounts for the frequent volcano and earthquakes there.

  1. Inflammatory bowel disease in children of middle eastern descent.

    Science.gov (United States)

    Naidoo, Christina Mai Ying; Leach, Steven T; Day, Andrew S; Lemberg, Daniel A

    2014-01-01

    Increasing rates of inflammatory bowel disease (IBD) are now seen in populations where it was once uncommon. The pattern of IBD in children of Middle Eastern descent in Australia has never been reported. This study aimed to investigate the burden of IBD in children of Middle Eastern descent at the Sydney Children's Hospital, Randwick (SCHR). The SCHR IBD database was used to identify patients of self-reported Middle Eastern ethnicity diagnosed between 1987 and 2011. Demographic, diagnosis, and management data was collected for all Middle Eastern children and an age and gender matched non-Middle Eastern IBD control group. Twenty-four patients of Middle Eastern descent were identified. Middle Eastern Crohn's disease patients had higher disease activity at diagnosis, higher use of thiopurines, and less restricted colonic disease than controls. Although there were limitations with this dataset, we estimated a higher prevalence of IBD in Middle Eastern children and they had a different disease phenotype and behavior compared to the control group, with less disease restricted to the colon and likely a more active disease course.

  2. The eastern Asian and eastern and western North American floristic disjunction: congruent phylogenetic patterns in seven diverse genera.

    Science.gov (United States)

    Xiang, Q Y; Soltis, D E; Soltis, P S

    1998-10-01

    One of the most remarkable examples of intercontinental disjunction of the North Temperate Flora involves eastern Asia and eastern and western North America. Although there has been considerable interest in this phytogeographic pattern for over 150 years (e.g., Gray, 1859; Li, 1952; Graham, 1972; Boufford and Spongberg, 1983; Wu, 1983; Tiffney, 1985a, 1985b), relationships among taxa displaying the disjunction remain obscure. Understanding phylogenetic relationships is, however, a prerequisite for historical biogeographic analyses of this distributional pattern. To understand better the relationships of taxa displaying this intercontinental disjunction, phylogenetic analyses were conducted using a variety of DNA data sets for species of four genera (Cornus, Boykinia, Tiarella, and Trautvetteria) that occur in eastern Asia, eastern North America, and western North America. An area cladogram was constructed for each of the four genera, all of which show a similar pattern of relationship: the eastern Asian species are sister to all North American species. An identical phylogenetic pattern is also found in three other taxa exhibiting this disjunction (Aralia sect. Aralia, Calycanthus, and Adiantum pedatum). The congruent phylogenetic pattern found in these seven diverse genera raises the possibility of a common origin of the eastern Asia, eastern and western North America disjunction. The data are in agreement with the long-standing hypothesis that this well-known floristic disjunction represents the fragmentation of a once continuous Mixed Mesophytic forest community and suggest that the disjunction may have involved only two major vicariance events: an initial split between Eurasia and North America, followed by the isolation of floras between eastern and western North America. However, congruence between phylogenies and geographic distributions does not necessarily indicate an identical phytogeographic history. Taxa exhibiting the same phylogenetic pattern may have

  3. The Mesoarchean Tiejiashan-Gongchangling potassic granite in the Anshan-Benxi area, North China Craton: Origin by recycling of Paleo- to Eoarchean crust from U-Pb-Nd-Hf-O isotopic studies

    Science.gov (United States)

    Dong, Chunyan; Wan, Yusheng; Xie, Hangqiang; Nutman, Allen P.; Xie, Shiwen; Liu, Shoujie; Ma, Mingzhu; Liu, Dunyi

    2017-10-01

    Mesoarchean and older potassic granites are important indicators of recycling of ancient continental crust early in Earth's history. This study of integrated whole rock and zircon geochemistry and geochronology reports the age and identification of the source materials of the > 200 km2 Mesoarchean Tiejiashan-Gongchangling granite in the Anshan-Benxi area, North China Craton, the largest pre-Neoarchean granite domain in the craton. SHRIMP U-Pb zircon dating on 15 samples indicates the magmatic crystallization of the granites between 2.95 and 3.0 Ga and reveals a superimposed tectonothermal event at 2.91 Ga. The granites are characterized by high SiO2 and K2O, low CaO, FeOt, MgO and TiO2 with peraluminuous features. They show large variations in (La/Yb)n and strong negative Eu and Ba anomalies and Nb, P and Ti depletions. Whole rock Nd and magmatic zircon Hf isotopic compositions show large variations, but with most having εNd(t) and εHf(t) values recycling of Paleo- to Eoarchean continental material in an intracontinental environment, with little if any contribution from Mesoarchean mantle sources. The sources could be predominantly unaltered ancient gneisses, together with yet to be identified Paleo- to Eoarchean materials affected by early low temperature alteration (weathered rocks or clastic sediment).

  4. Petrography and geochronology (U/Pb-Sm/Nd) the Passagem Granite, Pensamiento Granitoid Complex, Paragua Terrane, SW Amazon Craton, Mato Grosso, Brazil; Petrologia e geocronologia (U/Pb-Sm/Nd) do Granito Passagem, Complexo Granitoide Pensamiento, SW do Craton Amazonico (MT)

    Energy Technology Data Exchange (ETDEWEB)

    Jesus, Gisely Carmo de, E-mail: giselycarmo@hotmail.co [Universidade Federal de Mato Grosso (ICET/UFMT), Cuiaba, MT (Brazil). Inst. de Ciencias Exatas e da Terra. Programa de Pos-Graduacao em Geociencias; Sousa, Maria Zelia Aguiar de, E-mail: mzaguiar@terra.com.b [Universidade Federal de Mato Grosso(ICET/UFMT), Cuiaba, MT (Brazil). Inst. de Ciencias Exatas e da Terra. Dept. de Recursos Minerais; Ruiz, Amarildo Salina; Matos, Joao Batista de, E-mail: asruiz@gmail.co, E-mail: jmatos@cpd.ufmt.b [Universidade Federal de Mato Grosso (ICET/UFMT), Cuiaba, MT (Brazil). Inst. de Ciencias Exatas e da Terra. Dept. de Geologia Geral

    2010-09-15

    The Passagem granite includes stocks, plugs and dikes located in the Ricardo Franco hill - Vila Bela da Santissima Trindade region - state of Mato Grosso, central Brazil. The Passagem Granite is included in the Paragua terrane - SW Amazonian Craton. It consists of isotropic monzogranite, sienogranite and more rarely granodiorites with leucocratic dark gray to white color. These rocks range from hypidomorphic inequigranular to xenomorphic texture, fine to medium grained. Biotite is the only primary mafic present as essential phase and characterize an expanded slightly acid sequence formed by a sub-alkaline magmatism of high-potassium calc-alkaline, slightly peraluminous composition from arc magmatic tectonic environment during a post-collisional period. Mechanism of fractional crystallization of plagioclase, biotite, titanite, apatite and zircon associated with simultaneous crustal assimilation are suggested for the evolution of these rocks. The results support the hypothesis of a post-collisional magmatism in the Paragua terrane at 1284 +- 20 Ma corresponding to the crystallization age of the Passagem granite. This paper propose that Passagem Granite represents as an extension in Brazilian terrane of the Pensamiento Granitoid Complex. (author)

  5. Rhinoplasty in Middle Eastern Patients.

    Science.gov (United States)

    Sajjadian, Ali

    2016-01-01

    Rhinoplasty in patients of Middle Eastern origin requires complete understanding of nasal morphology and an individualized approach to create a racially congruent and aesthetically pleasing outcome. In this article, common anatomic features and characteristics and detailed steps, surgical techniques, and operative maneuvers that can lead to predictable outcome in rhinoplasty of Middle Eastern patients are discussed. Copyright © 2016 Elsevier Inc. All rights reserved.

  6. Middle Eastern Christians in Europe

    DEFF Research Database (Denmark)

    Sparre, Sara Cathrine Lei; Hunter, Alistair; Jørgensen, Anne Rosenlund

    This booklet, published in English, Danish, Swedish and Arabic, has the aim to present overall findings of the research project Defining and Identifying Middle Eastern Christians in Europe (DIMECCE) to a broader audience.......This booklet, published in English, Danish, Swedish and Arabic, has the aim to present overall findings of the research project Defining and Identifying Middle Eastern Christians in Europe (DIMECCE) to a broader audience....

  7. Eastern Africa Social Science Research Review: Contact

    African Journals Online (AJOL)

    Eastern Africa Social Science Research Review: Contact. Journal Home > About the Journal > Eastern Africa Social Science Research Review: Contact. Log in or Register to get access to full text downloads.

  8. Structure of the mantle lithosphere in continental collision zones of Europe, North America and China from S-receiver functions

    Science.gov (United States)

    Kind, R.; Shen, X.

    2017-12-01

    Seismic tomography and receiver functions are the most common methods to study the structure of the mantle lithosphere. We use S-receiver functions to study continent-continent collision zones in Europe, North America and China. In order to avoid possible numerical problems caused by filtering effects (side lobes) we process the data practically without filtering (also excluding deconvolution). Side lobes are still a fundamental question to check the reality of the Mid-Lithospheric Discontinuity (MLD). We use openly available data of mostly permanent seismic broadband stations from the European portal EIDA, from IRIS and from the Chinese Seismic Network. We obtained several ten thousands of useful records in each region by visual and fully automatic processing. We observed the MLD in all cratonic regions near 100 km depth and the Lithosphere-Asthenosphere Boundary (LAB) partly in cratonic regions near 200 km depth. The observation of the cratonic LAB with converted waves requires a relatively sharp discontinuity which excludes temperature as only cause of the LAB. In younger tectonic active regions we observed the LAB near 100 km depth. TheLAB and MLD are in collision zones significantly structured. In central Europe we observed the deep cratonic LAB reaching far to the west of the Tornquist-Teisseyre Zone below Phanerozoic cover. Below the northern edge of the Bohemian Massif seems to be a tear in the LAB leading to a jump in its depth of about 100 km. In North America we see north of Yellowstone a smooth deepening of the western LAB from about 100 km depth to 200 km depth at the Mid-Continental Rift System. Similarly to the LAB jump below the Bohemian Massif in Europe, we see below the Sevier Thrust Belt also a jump of about 100 km in the LAB depth. In China we see the cratonic LAB deepening to the south-west far below eastern Tibet. Below the craton in north-east China is only the shallow LAB/MLD visible. These observations in three continents show that the

  9. Eastern Africa Social Science Research Review

    African Journals Online (AJOL)

    The Eastern Africa Social Science Research Review (EASSRR) is a bi-annual journal published by the Organization for Social Science Research in Eastern Africa (OSSREA). Since the publication of its maiden ... Emerging regions in Ethiopia: are they catching up with the rest of Ethiopia? EMAIL FULL TEXT EMAIL FULL ...

  10. Babesia microti infection, eastern Pennsylvania, USA.

    Science.gov (United States)

    Acosta, Marcela E Perez; Ender, Peter T; Smith, Erin M; Jahre, Jeffrey A

    2013-07-01

    Infection with Babesia microti has not been well-described in eastern Pennsylvania, USA, despite the vector of this organism being prevalent. We report 3 cases of babesiosis in eastern Pennsylvania in persons without recent travel outside the region or history of blood transfusions, suggesting emergence of this infection.

  11. 76 FR 7833 - Texas Eastern Transmission, LP; Notice of Application

    Science.gov (United States)

    2011-02-11

    ...] Texas Eastern Transmission, LP; Notice of Application Take notice that on January 25, 2011, Texas Eastern Transmission, LP (Texas Eastern), 5400 Westheimer Court, Houston, Texas 77056, filed in the above... TEAM 2012 Project. Specifically, Texas Eastern requests: (i) Authorization under NGA sections 7(b) and...

  12. 78 FR 43874 - Texas Eastern Transmission, LP; Notice of Application

    Science.gov (United States)

    2013-07-22

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP13-514-000] Texas Eastern Transmission, LP; Notice of Application On July 2, 2013, Texas Eastern Transmission, LP (Texas Eastern) filed... natural gas facilities no longer in service. As described more fully in the Application, Texas Eastern...

  13. Isotopic and chemical evidence for three accretionary magmatic arcs ( 1.79 - 1.42 Ga) in the SW Amazon Craton, Mato Grosso State, Brazil

    International Nuclear Information System (INIS)

    Geraldes, Mauro Cesar; Teixeira, Wilson; Schmus, William Randall van

    2000-01-01

    Twenty-one U/Pb ages of granitoids in the SW Amazon craton define three crustal accretionary events during the Paleo-and Mesoproterozoic that represent significant portions of the Rio Negro-Juruena Province and the Rondonian/San Ignacio province. Two events refer to the Rio Negro-Juruena province: The Alto Jauru greenstone belt comprises acid volcanics and tonalite to granite gneisses with U/Pb ages from 1790 to 1750 Ma. Sm/Nd isotopic data (e N -d (t) from +2.6 to +2.2 and T DM from 2.0 to 1.80 Ga) indicate a volcanic arc with juvenile signatures for these units. The second event (Cachoeirinha arc) comprises granites to tonalites with U/Pb ages from 1580 to 1530 Ma. Sm/Nd results. (author)

  14. 76 FR 41755 - Eastern Arizona Counties Resource Advisory; Meeting

    Science.gov (United States)

    2011-07-15

    ... DEPARTMENT OF AGRICULTURE Forest Service Eastern Arizona Counties Resource Advisory; Meeting AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Eastern Arizona Counties Resource... FURTHER INFORMATION CONTACT: Julia Faith Rivera, RAC Program Manager, Eastern Arizona Counties Resource...

  15. Eastern Orthodox perspectives on violence

    DEFF Research Database (Denmark)

    Hilton Saggau, Emil

    2017-01-01

    Abstract: In the post-communist era, the contemporary national Eastern Orthodox churches have often been accused of taking either direct or ideological part in violence across Eastern Europe. In several scholarly analyses, the churches have been linked with ethnic and national violence. They have...... thus been identified as an ideological root for a distinctive ethno-religious nationalism either blocking the way for a pluralistic society or simply defying it. These cases of violence and conflicts, as well as their subsequent analysis, only point to a practical and visible manifestation of conflicts......, and they therefore don’t answer a broader theological question, namely the question of the general position of the Eastern Orthodox churches regarding violence. This article will address this broader question of what the Orthodox churches’ position is on violence and discuss the co-relation and intersection between...

  16. 76 FR 28210 - Eastern Arizona Counties Resource Advisory Committee

    Science.gov (United States)

    2011-05-16

    ... DEPARTMENT OF AGRICULTURE Forest Service Eastern Arizona Counties Resource Advisory Committee AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Eastern Arizona Counties will meet...: Julia Faith Rivera, RAC Program Manager, Eastern Arizona Counties Resource Advisory Committee, Apache...

  17. 75 FR 18145 - Eastern Arizona Counties Resource Advisory Committee

    Science.gov (United States)

    2010-04-09

    ... DEPARTMENT OF AGRICULTURE Forest Service Eastern Arizona Counties Resource Advisory Committee AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Eastern Arizona Counties Resource... Rivera, Coordinator, Eastern Arizona Counties Resource Advisory Committee, c/o Forest Service, USDA, P.O...

  18. Inclusions in diamonds constrain thermo-chemical conditions during Mesozoic metasomatism of the Kaapvaal cratonic mantle

    Science.gov (United States)

    Weiss, Yaakov; Navon, Oded; Goldstein, Steven L.; Harris, Jeff W.

    2018-06-01

    ) differs as well. The fO2 calculated for the saline HDF compositions (Δlog ⁡ fO 2 (FMQ) = - 2.47 to -1.34) are higher by about a log unit compared with that recorded by xenoliths at 4-7 GPa. We conclude that enriched saline HDFs mediated the metasomatism that preceded Group I kimberlite eruptions in the southwestern Kaapvaal craton, and that their 'cold and oxidized' nature reflects their derivation from a deep subducting slab. This event had little impact on the temperature and redox state of the Kaapvaal lithosphere as a reservoir, however, it likely affected its properties along limited metasomatized veins and their wall rock. To reconcile the temperature and oxygen fugacity discrepancy between inclusions in diamonds and xenoliths, we argue that xenoliths did not equilibrate during the last saline metasomatic event or kimberlite eruption. Thus the P-T- fO2 gradients they record express pre-existing lithospheric conditions that were likely established during the last major thermal event in the Kaapvaal craton (i.e. the Karoo magmatism at ca. 180 Ma).

  19. THE EASTERN PARTNERSHIP – A PREMISE FOR AN ENHANCED EU-EASTERN NEIGHBOURS COOPERATION RELATIONSHIP

    Directory of Open Access Journals (Sweden)

    Oana Mocanu

    2009-12-01

    Full Text Available The enlargement of the European Union towards the Central and Eastern Europe has brought to attention the necessity to reshape the EU institutional framework and specific policies addressing its new neighbourhood. Repeatedly stating that the European Neighbourhood Policy (ENP is not a preceding phase for membership, the European Union also embraced the Polish-Swedish initiative for an Eastern Partnership (EaP. Meant at first to counterbalance the Union for Mediterranean project, the EaP has developed into a distinct project, with specific and ambitious cooperation goals, a positive and constructive agenda meant to support six countries (Ukraine, Moldova, Georgia, Azerbaijan, Armenia and Belarus develop and harmonize with the European standards and, at the same, attempting to build and further develop an Eastern dimension of the ENP. The questions of the efficiency of the conditionality derived from the EaP and also the complementarity of this initiative with other regional projects in the area can also be important matters of concern.

  20. Ethnographies of Grey Zones in Eastern Europe

    DEFF Research Database (Denmark)

    Over the last two decades, Eastern Europe has experienced extensive changes in geo-political relocations and relations leading to everyday uncertainty. Attempts to establish liberal democracies, re-orientations from planned to market economics, and a desire to create ‘new states’ and internationa......Over the last two decades, Eastern Europe has experienced extensive changes in geo-political relocations and relations leading to everyday uncertainty. Attempts to establish liberal democracies, re-orientations from planned to market economics, and a desire to create ‘new states...... contemporary Eastern Europe....

  1. Ethnographies of Grey Zones in Eastern Europe:

    DEFF Research Database (Denmark)

    Over the last two decades, Eastern Europe has experienced extensive changes in geo-political relocations and relations leading to everyday uncertainty. Attempts to establish liberal democracies, re-orientations from planned to market economics, and a desire to create ‘new states’ and internationa......Over the last two decades, Eastern Europe has experienced extensive changes in geo-political relocations and relations leading to everyday uncertainty. Attempts to establish liberal democracies, re-orientations from planned to market economics, and a desire to create ‘new states...... contemporary Eastern Europe....

  2. Transcultural Memory in Eastern European Migrant Literature

    DEFF Research Database (Denmark)

    Ortner, Jessica

    of the major processes that circulate memories across cultural and national borderlines. This paper will investigate the circulation of memories in Eastern Europe migrant-literature that since 2000 has become an increasingly influential literary tendency in Germany. Articulating an eastern perspective...... consciously follow the mission to “enlighten and inform Western readers about their eastern neighbours” (Haines 2008). Causing an “eastern enlargement” of German literature (Bürger-Koftis 2008), the wave of migrant authors broadens Germany’s cultural memory by supplementing it with “new” memories. Furthermore......The “transcultural turn” of memory studies focuses on the fluid and dynamic aspects of cultural memory. This paper is concerned with the traveling of memories along the paths of migration. As migrants carry along “collective images and narratives of the past” (Erll 2011), migration is one...

  3. Transition Metal Systematics of Opx-Enriched Harzburgites From the Cascades Arc With Implications for the Origin of Cratonic Peridotites

    Science.gov (United States)

    Turner, S. J.

    2007-12-01

    A number of peridotite xenoliths collected from the Simcoe volcanic field region of the Cascades arc exhibit notable enrichment of modal orthopyroxene. The process driving this enrichment is most likely metasomatism of the mantle wedge by Si-rich fluids derived ultimately from the underlying slab. By investigating the resultant elemental systematics associated with subduction zone metasomatism of this type, we hope to shed light on the origin of other opx-rich peridotites, such as those seen in many cratonic xenolith suites. The xenoliths found in the Simcoe volcanic field provide a rare opportunity to examine the composition of sub arc mantle, as it is unusual to find mantle xenoliths in volcanic arc lavas. The samples were analyzed using laser ablation ICPMS and their bulk compositions were reconstructed from point-counted mineral modes. Two-pyroxene mineral thermometry of the samples yield temperatures of approximately 1000 degrees C, corresponding to a depth of origin at uppermost mantle pressures if typical arc geotherms are assumed. Most of the peridotites are harzburgites or olivine-orthopyroxenites (Mg#s 0.88-0.9; opx mode 0.15-0.9), with small amounts of clinopyroxene (rare earths, consistent with a metasomatic origin for these opx-rich harzburgites. Of note is the counterintuitive systematics of Zn. Whole-rock Zn decreases with opx, but Zn in olivine also decreases with opx mode while Zn in opx increases with opx mode, hence the decrease in whole- rock Zn is not simply due to mechanical segregation of harzburgite into opx- and ol-rich zones. In summary, the REE signatures suggest the subducting slab as the most likely candidate for the source of the fluids that caused the opx enrichment. The opx-enrichment itself and the unusual trends in Zn suggest a reaction between a silicic fluid and normal harzburgite. Moreover, the concomitant decrease in olivine and whole-rock Zn with opx mode suggests significant leaching of Zn from the peridotite during this

  4. A brief overview of state-of-the-art electronics in physical oceanographic instrumentation

    Digital Repository Service at National Institute of Oceanography (India)

    Charyulu, R.J.K.

    of B.Sc. (Physics, Maths) in 1970, B.E. (Tele- communication Engineering) in 1974 from colleges in Hospet & Gulbarga respectively both then affliated to Karnatak University, Dharwar. He received M.Tech. degree in Physical Engineering in 1976 from...

  5. Integrated fossil and molecular data reveal the biogeographic diversification of the eastern Asian-eastern North American disjunct hickory genus (Carya Nutt.).

    Science.gov (United States)

    Zhang, Jing-Bo; Li, Rui-Qi; Xiang, Xiao-Guo; Manchester, Steven R; Lin, Li; Wang, Wei; Wen, Jun; Chen, Zhi-Duan

    2013-01-01

    The hickory genus (Carya) contains ca. 17 species distributed in subtropical and tropical regions of eastern Asia and subtropical to temperate regions of eastern North America. Previously, the phylogenetic relationships between eastern Asian and eastern North American species of Carya were not fully confirmed even with an extensive sampling, biogeographic and diversification patterns had thus never been investigated in a phylogenetic context. We sampled 17 species of Carya and 15 species representing all other genera of the Juglandaceae as outgroups, with eight nuclear and plastid loci to reconstruct the phylogeny of Carya. The phylogenetic positions of seven extinct genera of the Juglandaceae were inferred using morphological characters and the molecular phylogeny as a backbone constraint. Divergence times within Carya were estimated with relaxed Bayesian dating. Biogeographic analyses were performed in DIVA and LAGRANGE. Diversification rates were inferred by LASER and APE packages. Our results support two major clades within Carya, corresponding to the lineages of eastern Asia and eastern North America. The split between the two disjunct clades is estimated to be 21.58 (95% HPD 11.07-35.51) Ma. Genus-level DIVA and LAGRANGE analyses incorporating both extant and extinct genera of the Juglandaceae suggested that Carya originated in North America, and migrated to Eurasia during the early Tertiary via the North Atlantic land bridge. Fragmentation of the distribution caused by global cooling in the late Tertiary resulted in the current disjunction. The diversification rate of hickories in eastern North America appeared to be higher than that in eastern Asia, which is ascribed to greater ecological opportunities, key morphological innovations, and polyploidy.

  6. Integrated fossil and molecular data reveal the biogeographic diversification of the eastern Asian-eastern North American disjunct hickory genus (Carya Nutt..

    Directory of Open Access Journals (Sweden)

    Jing-Bo Zhang

    Full Text Available The hickory genus (Carya contains ca. 17 species distributed in subtropical and tropical regions of eastern Asia and subtropical to temperate regions of eastern North America. Previously, the phylogenetic relationships between eastern Asian and eastern North American species of Carya were not fully confirmed even with an extensive sampling, biogeographic and diversification patterns had thus never been investigated in a phylogenetic context. We sampled 17 species of Carya and 15 species representing all other genera of the Juglandaceae as outgroups, with eight nuclear and plastid loci to reconstruct the phylogeny of Carya. The phylogenetic positions of seven extinct genera of the Juglandaceae were inferred using morphological characters and the molecular phylogeny as a backbone constraint. Divergence times within Carya were estimated with relaxed Bayesian dating. Biogeographic analyses were performed in DIVA and LAGRANGE. Diversification rates were inferred by LASER and APE packages. Our results support two major clades within Carya, corresponding to the lineages of eastern Asia and eastern North America. The split between the two disjunct clades is estimated to be 21.58 (95% HPD 11.07-35.51 Ma. Genus-level DIVA and LAGRANGE analyses incorporating both extant and extinct genera of the Juglandaceae suggested that Carya originated in North America, and migrated to Eurasia during the early Tertiary via the North Atlantic land bridge. Fragmentation of the distribution caused by global cooling in the late Tertiary resulted in the current disjunction. The diversification rate of hickories in eastern North America appeared to be higher than that in eastern Asia, which is ascribed to greater ecological opportunities, key morphological innovations, and polyploidy.

  7. Nuclear power in Eastern Europe

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, S. (Sussex Univ., Brighton (UK). Science Policy Research Unit)

    1991-01-01

    The main aim of this article is that of illustrating the experience of the use of nuclear power in Eastern Europe in order to estimate the degree of adequacy or inadequacy of COMECON's nuclear technology. The author examines four areas of interest concerning: the feasibility of new orders for nuclear plants in Eastern Europe; the pros and cons of completing half-built nuclear power plants; current policy towards existing nuclear power plants; and a review of the available evidence on the operating performance of plants in Eastern Europe. The common belief that the nuclear power experience had by old COMECON countries is uniformly bad does not seem to be fully supported by the limited evidence available. In the author's opinion, the prospects for a successful nuclear power industry in these countries depends on a series on interdependent factors among which, human skills hold a prominent position.

  8. Strategy Formation in Eastern Jutland

    DEFF Research Database (Denmark)

    Olesen, Kristian

    2008-01-01

      In Eastern Jutland a strategy formation process has been initiated with the aim of developing a strategic spatial plan for the city region.  An organisation has been set up to deal with the first phase of the process, which is to carry out three functional analyses and prepare a common vision...... in the area.   The municipalities acknowledge the articulation of the city region and the initiated planning process.  However, the municipalities might see the arena as means to lobby for infrastructure investments in Eastern Jutland, as it is doubtful whether the municipalities will feel encouraged to enter...... a process, which is aiming at increasing the national regulation within their territory.    The result might very well be that the discussion about future infrastructure investments is not linked to discussions about future urban development in Eastern Jutland.  These aspects raises serious questions about...

  9. 77 FR 51966 - Eastern Arizona Resource Advisory Committee

    Science.gov (United States)

    2012-08-28

    ... DEPARTMENT OF AGRICULTURE Forest Service Eastern Arizona Resource Advisory Committee AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Eastern Arizona Resource Advisory Committee...

  10. POLITICAL PROCESS DRIVERS OF CORRUPTION IN EASTERN EUROPE

    Directory of Open Access Journals (Sweden)

    Ada-Iuliana POPESCU

    2016-12-01

    Full Text Available Corruption stands as one of the many obstacles to the political and economic security of the Eastern European region. Thus, despite the political and economic instability in the region, Eastern European countries, in and outside of the European Union need to fight corruption collectively and individually. The task is difficult, but hope is justified because the causes of corruption in this part of the region are similar and anti-corruption expertise is available. We believe that a deeper analysis of corruption’s drivers can produce a better articulated and more efficient anti-corruption strategy. This strategy will create an anti-corruption infrastructure that will strengthen the Eastern European Partnership. As a prelude to the deeper analysis that we believe must be a part of this strategy, this paper identifies the main drivers of corruption in the Eastern European Partnership countries and explains why addressing these drivers will strengthen the Eastern European Partnership.

  11. Metallogenesis and tectonics of the Russian Far East, Alaska, and the Canadian Cordillera

    Science.gov (United States)

    Nokleberg, Warren J.; Bundtzen, Thomas K.; Eremin, Roman A.; Ratkin, Vladimir V.; Dawson, Kenneth M.; Shpikerman, Vladimir I.; Goryachev, Nikolai A.; Byalobzhesky, Stanislav G.; Frolov, Yuri F.; Khanchuk, Alexander I.; Koch, Richard D.; Monger, James W.H.; Pozdeev, Anany I.; Rozenblum, Ilya S.; Rodionov, Sergey M.; Parfenov, Leonid M.; Scotese, Christopher R.; Sidorov, Anatoly A.

    2005-01-01

    The Proterozoic and Phanerozoic metallogenic and tectonic evolution of the Russian Far East, Alaska, and the Canadian Cordillera is recorded in the cratons, craton margins, and orogenic collages of the Circum-North Pacific mountain belts that separate the North Pacific from the eastern North Asian and western North American Cratons. The collages consist of tectonostratigraphic terranes and contained metallogenic belts, which are composed of fragments of igneous arcs, accretionary-wedge and subduction-zone complexes, passive continental margins, and cratons. The terranes are overlapped by continental-margin-arc and sedimentary-basin assemblages and contained metallogenic belts. The metallogenic and geologic history of terranes, overlap assemblages, cratons, and craton margins has been complicated by postaccretion dismemberment and translation during strike-slip faulting that occurred subparallel to continental margins. Seven processes overlapping in time were responsible for most of metallogenic and geologic complexities of the region (1) In the Early and Middle Proterozoic, marine sedimentary basins developed on major cratons and were the loci for ironstone (Superior Fe) deposits and sediment-hosted Cu deposits that occur along both the North Asia Craton and North American Craton Margin. (2) In the Late Proterozoic, Late Devonian, and Early Carboniferous, major periods of rifting occurred along the ancestral margins of present-day Northeast Asia and northwestern North America. The rifting resulted in fragmentation of each continent, and formation of cratonal and passive continental-margin terranes that eventually migrated and accreted to other sites along the evolving margins of the original or adjacent continents. The rifting also resulted in formation of various massive-sulfide metallogenic belts. (3) From about the late Paleozoic through the mid-Cretaceous, a succession of island arcs and contained igneous-arc-related metallogenic belts and tectonically paired

  12. Eastern Europe's market role

    International Nuclear Information System (INIS)

    Schreiber, K.F.

    1991-01-01

    Until the late 1980s, trade in nuclear fuel between market economy countries and those with planned economies was limited. The exception to this was in the enrichment market across Western Europe during the 1970s. Most of the nuclear generating plants in the Soviet Union and Eastern Europe are light water reactors needing enriched uranium. Under the fuel supply agreements with Eastern Europe, the Soviet Union has provided all of the regions' enrichment services, and therefore it has developed the only enrichment facilities. Techsnabexport (TENEX), the USSR foreign trade organization for the nuclear fuel cycle, first appeared in the early 1970s. It was as an alternative supplier to the US government, which had a monopoly in the West regarding enrichment. In 1986 the USSR entered and soon dominated the spot market for enrichment. Political changes in Eastern Europe at the end of 1989 and throughout 1990 opened the nuclear fuel market even wider. In 1990 the USSR began allowing exports of concentrates, as well as enriched product, and a free flow of trade to the Western market is now developing for both enrichment and uranium. (author)

  13. 78 FR 6319 - Eastern Hydroelectric Corporation; Notice Rejecting Request for Rehearing

    Science.gov (United States)

    2013-01-30

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Project No. 7019-068] Eastern... an order amending license Article 401 for Eastern Hydroelectric Corporation's (Eastern Hydroelectric....\\1\\ On January 11, 2013, Eastern Hydroelectric filed a request for rehearing of Commission staff's...

  14. Inclusions of crichtonite-group minerals in Cr-pyropes from the Internatsionalnaya kimberlite pipe, Siberian Craton: Crystal chemistry, parageneses and relationships to mantle metasomatism

    Science.gov (United States)

    Rezvukhin, Dmitriy I.; Malkovets, Vladimir G.; Sharygin, Igor S.; Tretiakova, Irina G.; Griffin, William L.; O'Reilly, Suzanne Y.

    2018-05-01

    Cr-pyrope xenocrysts and associated inclusions of crichtonite-group minerals from the Internatsionalnaya kimberlite pipe were studied to provide new insights into processes in the lithospheric mantle beneath the Mirny kimberlite field, Siberian craton. Pyropes are predominantly of lherzolitic paragenesis (Cr2O3 2-6 wt%) and have trace-element spectra typical for garnets from fertile mantle (gradual increase in chondrite-normalized values from LREE to MREE-HREE). Crichtonite-group minerals commonly occur as monomineralic elongated inclusions, mostly in association with rutile, Mg-ilmenite and Cr-spinel within individual grains of pyrope. Sample INT-266 hosts intergrowth of crichtonite-group mineral and Cl-apatite, while sample INT-324 contains polymineralic apatite- and dolomite-bearing assemblages. Crichtonite-group minerals are Al-rich (1.1-4.5 wt% Al2O3), moderately Zr-enriched (1.3-4.3 wt% ZrO2), and are Ca-, Sr-, and occasionally Ba-dominant in terms of A-site occupancy; they also contain significant amounts of Na and LREE. T-estimates and chemical composition of Cr-pyropes imply that samples represent relatively low-T peridotite assemblages with ambient T ranging from 720 to 820°С. Projected onto the 35 mW/m2 cratonic paleogeotherm for the Mirny kimberlite field (Griffin et al., 1999b. Tectonophysics 310, 1-35), temperature estimates yield a P range of 34-42 kbar ( 110-130 km), which corresponds to a mantle domain in the uppermost part of the diamond stability field. The presence of crichtonite-group minerals in Cr-pyropes has petrological and geochemical implications as evidence for metasomatic enrichment of some incompatible elements in the lithospheric mantle beneath the Mirny kimberlite field. The genesis of Cr-pyropes with inclusions of crichtonite-group minerals is attributed to the percolation of Ca-Sr-Na-LREE-Zr-bearing carbonate-silicate metasomatic agents through Mg- and Cr-rich depleted peridotite protoliths. The findings of several potentially

  15. Petrogenesis of siliceous high-Mg series rocks as exemplified by the Early Paleoproterozoic mafic volcanic rocks of the Eastern Baltic Shield: enriched mantle versus crustal contamination

    Science.gov (United States)

    Bogina, Maria; Zlobin, Valeriy; Sharkov, Evgenii; Chistyakov, Alexeii

    2015-04-01

    The Early Paleoproterozoic stage in the Earth's evolution was marked by the initiation of global rift systems, the tectonic nature of which was determined by plume geodynamics. These processes caused the voluminous emplacement of mantle melts with the formation of dike swarms, mafic-ultramafic layered intrusions, and volcanic rocks. All these rocks are usually considered as derivatives of SHMS (siliceous high-magnesian series). Within the Eastern Baltic Shield, the SHMS volcanic rocks are localized in the domains with different crustal history: in the Vodlozero block of the Karelian craton with the oldest (Middle Archean) crust, in the Central Block of the same craton with the Neoarchean crust, and in the Kola Craton with a heterogeneous crust. At the same time, these rocks are characterized by sufficiently close geochemical characteristics: high REE fractionation ((La/Yb)N = 4.9-11.7, (La/Sm)N=2.3-3.6, (Gd/Yb)N =1.66-2.74)), LILE enrichment, negative Nb anomaly, low to moderate Ti content, and sufficiently narrow variations in Nd isotope composition from -2.0 to -0.4 epsilon units. The tectonomagmatic interpretation of these rocks was ambiguous, because such characteristics may be produced by both crustal contamination of depleted mantle melts, and by generation from a mantle source metasomatized during previous subduction event. Similar REE patterns and overlapping Nd isotope compositions indicate that the studied basaltic rocks were formed from similar sources. If crustal contamination en route to the surface would play a significant role in the formation of the studied basalts, then almost equal amounts of contaminant of similar composition are required to produce the mafic rocks with similar geochemical signatures and close Nd isotopic compositions, which is hardly possible for the rocks spaced far apart in a heterogeneous crust. This conclusion is consistent with analysis of some relations between incompatible elements and their ratios. In particular, the

  16. Ichnologic evidence of a Cambrian age in the southern Amazon Craton: Implications for the onset of the Western Gondwana history

    Science.gov (United States)

    Santos, Hudson P.; Mángano, M. Gabriela; Soares, Joelson L.; Nogueira, Afonso C. R.; Bandeira, José; Rudnitzki, Isaac D.

    2017-07-01

    Colonization of the infaunal ecospace by burrowing bilaterians is one of the most important behavioral innovations during the Ediacaran-Cambrian transition. The establishment of vertical burrows by suspension feeders in high-energy nearshore settings during Cambrian Age 2 is reflected by the appearance of the Skolithos Ichnofacies. For the first time, unquestionable vertical burrows typical of the Skolithos Ichnofacies, such as Skolithos linearis, Diplocraterion parallelum and Arenicolites isp., are recorded from nearshore siliciclastic deposits of the Raizama Formation, southeastern Amazon Craton, Brazil. Integration of ichnologic and sedimentologic datasets suggests that these trace fossils record colonization of high-energy and well-oxygenated nearshore sandy environments. Chronostratigraphically, the presence of these vertical burrows indicates an age not older than early Cambrian for the Raizama Formation, which traditionally has been regarded as Ediacaran. Therefore, the Raizama ichnofauna illustrates the advent of modern Phanerozoic ecology marked by the Agronomic Revolution. The discovery of the Skolithos Ichnofacies in these shallow-marine strata suggests possible connections between some central Western Gondwana basins.

  17. Mesozoic mafic dikes from the Shandong Peninsula, North China Craton: Petrogenesis and tectonic implications

    International Nuclear Information System (INIS)

    Liu Shen; Hu Ruizhong; Zhao Junhong; Feng Caixia; Zou, Haibo

    2006-01-01

    Mesozoic mafic dikes are widely distributed in Luxi (Mengyin and Zichuan) and Jiaodong regions of the Shandong Peninsula, China, providing an opportunity of investigating the nature of the lost lithospheric mantle beneath the North China Craton (NCC). The mafic dikes are characterized by strong depletion in high field strength elements (HFSE), enrichment in light rare earth elements (LREE), highly variable Th/U ratios, high initial ( 87 Sr/ 86 Sr) i (0.7050-0.7099) and negative ε Nd (T) (-6.0 to -17.6). They were derived from melting of metasomatized portions of the subcontinental lithospheric mantle, followed by fractionation of clinopyroxenes. The similarity in Nd isotopic compositions between the Mengyin gabbro dikes and the Paleozoic peridotite xenoliths suggests that ancient lithospheric mantle was still retained at 120 Ma below Mengyin, although the ancient lithospheric mantle in many other places beneath NCC had been severely modified. There might be multiple enrichment events in the lithospheric mantle. An early-stage (before or during Paleozoic) rutile-rich metasomatism affected the lithospheric mantle below Mengyin, Jiaodong and Zichuan. Since then, the lithospheric mantle beneath Mengyin was isolated. A late-stage metasomatism by silicate melts modified the lithospheric mantle beneath Jiaodong and Zichuan but not Mengyin. The removal of the enriched lithospheric mantle and the generation of the mafic dikes may be mainly related to the convective overturn accompanying Jurassic-Cretaceous subduction of the paleo-Pacific plate. (author)

  18. U-Pb age constraints for the La Tuna Granite and Montevideo Formation (Paleoproterozoic, Uruguay): Unravelling the structure of the Río de la Plata Craton

    Science.gov (United States)

    Pamoukaghlián, Karina; Gaucher, Claudio; Frei, Robert; Poiré, Daniel G.; Chemale, Farid; Frei, Dirk; Will, Thomas M.

    2017-11-01

    The Río de la Plata Craton is a continental block that crops out in Uruguay, eastern Argentina, southernmost Brazil and Paraguay. It comprises in Uruguay the Piedra Alta, Tandilia and Nico Pérez terranes, separated by the Colonia and the Sarandí del Yí megashears. The La Tuna Granite, which intrudes the Araminda metasandstones in the Tandilia Terrane, was considered Cambrian in age and the intruded sandstones were assigned to the Neoproterozoic Piedras de Afilar Formation. We show that the granite is Paleoproterozoic in age and that the host metasandstones do not belong to the Piedras de Afilar Formation, but to the Paleoproterozoic Montevideo Formation. U-Pb LA ICP-MS of zircon ages for the La Tuna Granite yielded a concordant crystallization age of 2156 ± 26 Ma. Furthermore a metamorphic event at 2010 ± 9 Ma is revealed by Pb stepwise leaching dating of monazites. U-Pb detrital zircon ages of the host Araminda metasandstone yield an upper intercept discordia age of 2152 ± 29 Ma, which marks the intrusion of the La Tuna pluton, and which is in accordance with the zircon U-Pb LA ICP MS constraints. A concordant U-Pb detrital zircon age of 2465 ± 40 Ma provides a maximum depositional age constraint for the metapsammites. Comparing quartz arenites of the Ediacaran Piedras de Afilar Formation with the Araminda metaquartzites, we conclude that they are very similar regarding petrology but they differ in age and metamorphic overprint. Detrital zircons in quartz arenites of the Piedras de Afilar Formation show youngest ages of 1.0 Ga. On the other hand, detrital zircons recovered from the Araminda metasandstones and the age of the intruding granite allow interpreting a depositional age between 2465 and 2150 Ma. Nd model ages show crustal residence times in average more than 200 myr older for the Tandilia Terrane both in Uruguay and Argentina, with a significant Neoarchean component, which is lacking in the Piedra Alta Terrane. Whereas the Piedra Alta Terrane was

  19. tive conflict resolution mechanism in eastern Ethiopia

    African Journals Online (AJOL)

    eastern Ethiopia: The case of the Ittu ... The study was conducted in eastern Ethiopia where the Somali and ... Zigale Tamir Tenaw is assistant professor in the Department of Gender and Development ..... regional state in collaboration with the local people – aggravate the already ..... Resource Based Conflict Network,.

  20. Seropositivity of agents causing abortion in local goat breeds in Eastern and South-eastern Anatolia, Turkey

    OpenAIRE

    BABÜR, Cahit; Tan, Tolga; ATASEVEN, Lale; ATASEVEN, Veysel Soydal; OĞUZOĞLU, Tuba Çiğdem

    2006-01-01

    The epidemiological information has not been available on the seroprevalenceof agents causing abortion and genital tract infection in indigenousgoats of Eastern and South-eastern regions of Turkey, yet. In these regions,the goats have importance for local economy and their production of meat,milk and mohair. There are also differences of the husbandry and climateconditions between two regions. The objective of this study was to describethe seroprevalence and distribution of antibodies to agen...

  1. Proteomic landscape in Central and Eastern Europe: the 9th Central and Eastern European Proteomic Conference, Poznan, Poland

    Czech Academy of Sciences Publication Activity Database

    Gadher, S. J.; Marczak, L.; Luczak, M.; Stobiecki, M.; Widlak, P.; Kovářová, Hana

    2016-01-01

    Roč. 13, č. 1 (2016), s. 5-7 ISSN 1478-9450. [Central and Eastern European Proteomic Conference (CEEPC) /9./. Poznaň, 15.06.2015-18.06.2015] Institutional support: RVO:67985904 Keywords : Central and Eastern Proteomic Conference * proteomics * mass spectrometry imaging Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.849, year: 2016

  2. Eastern Africa Social Science Research Review: Site Map

    African Journals Online (AJOL)

    Eastern Africa Social Science Research Review: Site Map. Journal Home > About the Journal > Eastern Africa Social Science Research Review: Site Map. Log in or Register to get access to full text downloads.

  3. Eastern Redcedar Seedling Assessment

    Data.gov (United States)

    U.S. Environmental Protection Agency — Eastern redcedar tree seedling growth in response to various soil, nitrogen, and photosynthetic radiation characteristics. This dataset is associated with the...

  4. Depositional Record of the Bagua Basin, Northern Peru: Implications for Climate and Tectonic Evolution of Tropical South America

    Science.gov (United States)

    Moreno, F.; George, S. W. M.; Williams, L. A.; Horton, B. K.; Garzione, C. N.

    2015-12-01

    The Andes Mountains exert critical controls on the climate, hydrology, and biodiversity of South America. The Bagua Basin, a low elevation (400-600 m) intermontane basin in northern Peru, offers a unique opportunity to study the ecological, climatic, and structural evolution of the western topographic boundary of the Amazonian foreland. Situated between the Marañon fold-thrust belt of the Western Cordillera and basement block uplifts of the Eastern Cordillera, the Bagua region contains a protracted, semi-continuous record of Triassic through Pleistocene sedimentation. Whereas Triassic-Cretaceous marine deposits were potentially related to extension and regional thermal subsidence, a Paleocene-Eocene shift to shallow marine and fluvial systems marks the onset of foreland basin conditions. Oligocene-Miocene sedimentation corresponds to a braided-meandering fluvial system with exceptional development of paleosols. In this study, we use new detrital zircon U-Pb geochronologic and oxygen stable isotopic datasets to establish a chronology of pre-Andean and Andean processes within the Bagua Basin. Detrital zircon geochronology provides constraints on when the Western and Eastern cordilleras shed sediments into the basin. Syndepositional zircons within Eocene, Oligocene and Miocene strata provide key age control for a previously poorly constrained depositional chronology. Preliminary results suggest a dramatic provenance shift in which Paleocene deposits contain almost exclusively cratonic populations (500-1600 Ma) whereas Eocene deposits show a mix of syndepositional zircons from the magmatic arc, recycled Mesozoic zircons, and cratonic zircon populations. Oxygen stable isotopes (δ18O) of carbonate nodules from Neogene paleosols will help elucidate when the Eastern Cordillera became an orographic barrier intercepting moisture from the Amazon basin to the east. Together, these records will help uncover the history of tectonics and climate interaction in tropical South

  5. 76 FR 18210 - Texas Eastern Transmission, LP; Notice of Application

    Science.gov (United States)

    2011-04-01

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP11-138-000] Texas Eastern Transmission, LP; Notice of Application On March 15, 2011, Texas Eastern Transmission Corporation (Texas Eastern), 5400 Westheimer Court, Houston, Texas 77056-5310, filed with the Federal Energy Regulatory...

  6. Experience in implementing projects in Eastern Europe

    International Nuclear Information System (INIS)

    Weichard, A.; Bauer, I.; Rieck, R.; Ziehm, R.

    2007-01-01

    The article covers the present projects and activities in Eastern Europe of Nukem Technologies GmbH. The company's East European business began in 1973 in the field of uranium trading. After difficult negotiations in the period of the ''cold war'' it became possible to enter into an agreement with the Soviet foreign trade organization, Techsnabexport, about purchases of uranium for Western nuclear power plants. In the course of Nukem's realignment in the late 1980s, the focus was shifted more and more to the possibility of exporting into other countries the technologies developed and proven in Germany. This included countries in Eastern Europe. The situation changed abruptly with the political opening of Eastern Europe. A large potential market opened to Nukem as a supplier of technologies and plants for waste treatment and, later, the wider area of decommissioning. The partners in Eastern Europe were interested in proven, modern solutions. The ensuing success was also due to the fact that Nukem, in the early nineties, hired specialists from the new German federal states who had studied in the Soviet Union and were familiar with Russian technology, language, and culture. Soliciting analogous projects in the countries of Eastern Europe other than the former Soviet Union was begun in a parallel process. Very soon it turned out that also the interim storage of spent fuel elements constituted a potential market. (orig.)

  7. Prevalence of 1691G>A FV mutation in Poland compared with that in other Central, Eastern and South-Eastern European countries

    Directory of Open Access Journals (Sweden)

    Grażyna Adler

    2012-05-01

    Full Text Available The 1691G>A FV variant has been described as a common genetic risk factor in venous thromboembolism. The purpose of this study was to provide a further frequency value for 1691G>A FV in Poland and to collate summary data from Central (Poland, Czech, Slovakia, Eastern (Russia, Belarus, Ukraine and South-Eastern (Slovenia, Croatia, Bosnia and Herzegovina, Serbia, Montenegro, Macedonia, Bulgaria European countries. For this purpose in 2007 the 1691G>A FV variant was analyzed by polymerase chain reaction-restriction fragment length polymorphism from DNA collected in 2005-2006. We studied 650 subjects: 400 newborns and 250 older individuals (mean age 46.1 y from Poland and compared results with reports from other countries, as well as with the frequency trend of 845G>A HFE across South-Eastern European countries using centroid cities. From our 1691G>A FV study we identified 626 GG homozygotes, 23 GA heterozygotes, and i AA homozygote (n = 650, giving an A allele frequency of 1.9%, and a summed frequency value for Poland of 2.0% (n = 1588; the frequency in Central European countries was 3.9% (n = 4559, mostly due to the high value in the Czech Republic: 5.1% (n = 2819; the South-Eastern European countries had 2.5% (n = 2410. Among the Eastern European countries the 1691G>A FV allele frequency was 1.9% (n=791, between the South-Eastern and Eastern European countries there was no significant difference (p=0.17. We confirm that the 1691G>A FV allele frequency in Poland, as well as other countries compared, is significantly lower than that in Czech.

  8. Prevalence of 1691G>A FV mutation in Poland compared with that in other Central, Eastern and South-Eastern European countries.

    Science.gov (United States)

    Adler, Grażyna; Clark, Jeremy S C; Loniewska, Beata; Czerska, Ewa; Salkic, Nermin N; Ciechanowicz, Andrzej

    2012-05-01

    The 1691G>A FV variant has been described as a common genetic risk factor in venous thromboembolism. The purpose of this study was to provide a further frequency value for 1691G>A FV in Poland and to collate summary data from Central (Poland, Czech, Slovakia), Eastern (Russia, Belarus, Ukraine) and South-Eastern (Slovenia, Croatia, Bosnia and Herzegovina, Serbia, Montenegro, Macedonia, Bulgaria) European countries. For this purpose in 2007 the 1691G>A FV variant was analyzed by polymerase chain reaction-restriction fragment length polymorphism from DNA collected in 2005-2006. We studied 650 subjects: 400 newborns and 250 older individuals (mean age 46.1 y) from Poland and compared results with reports from other countries, as well as with the frequency trend of 845G>A HFE across South-Eastern European countries using centroid cities. From our 1691G>A FV study we identified 626 GG homozygotes, 23 GA heterozygotes, and 1 AA homozygote (n = 650), giving an A allele frequency of 1.9%, and a summed frequency value for Poland of 2.0% (n = 1588); the frequency in Central European countries was 3.9% (n = 4559), mostly due to the high value in the Czech Republic: 5.1% (n = 2819); the South-Eastern European countries had 2.5% (n = 2410). Among the Eastern European countries the 1691G>A FV allele frequency was 1.9% (n=791), between the South-Eastern and Eastern European countries there was no significant difference (p=0.17). We confirm that the 1691G>A FV allele frequency in Poland, as well as other countries compared, is significantly lower than that in Czech.

  9. 75 FR 4412 - Eastern States: Filing of Plats of Survey

    Science.gov (United States)

    2010-01-27

    ... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLES956000-L14200000-BJ0000] Eastern States... survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  10. 76 FR 49760 - Texas Eastern Transmission, LP; Notice of Application

    Science.gov (United States)

    2011-08-11

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP11-524-000] Texas Eastern Transmission, LP; Notice of Application Take notice that on July 29, 2011, Texas Eastern Transmission, LP (Texas Eastern), 5400 Westheimer Court, Houston, Texas 77056-5310, filed with the Federal Energy...

  11. 75 FR 65028 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2010-10-21

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... of survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  12. 76 FR 77846 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2011-12-14

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  13. 76 FR 55700 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2011-09-08

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  14. 78 FR 48900 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2013-08-12

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  15. 76 FR 45293 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2011-07-28

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  16. 76 FR 48882 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2011-08-09

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice Of... survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management--Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  17. 77 FR 30314 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2012-05-22

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior ACTION: Notice... the BLM-Eastern States office in Springfield, Virginia, 30 calendar days from the date of publication in the Federal Register. FOR FURTHER INFORMATION CONTACT: Bureau of Land Management-Eastern States...

  18. 75 FR 33635 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2010-06-14

    ... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLES956000-L14200000-BJ0000] Eastern States... described below in the BLM--Eastern States office in Springfield, Virginia, 30 calendar days from the date...--Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn: Cadastral Survey. SUPPLEMENTARY...

  19. 75 FR 42459 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2010-07-21

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  20. 75 FR 80069 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2010-12-21

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  1. 78 FR 64933 - Texas Eastern Transmission, LP; Notice of Application

    Science.gov (United States)

    2013-10-30

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP14-4-000] Texas Eastern Transmission, LP; Notice of Application Take notice that on October 10, 2013, Texas Eastern Transmission, (Texas Eastern), having its principal place of business at 5400 Westheimer Court, Houston, Texas, 77056...

  2. 76 FR 6816 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2011-02-08

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management--Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  3. 77 FR 58575 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2012-09-21

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice... the BLM-Eastern States office in Springfield, Virginia, 30 calendar days from the date of publication in the Federal Register. FOR FURTHER INFORMATION CONTACT: Bureau of Land Management-Eastern States...

  4. 76 FR 65533 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2011-10-21

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... of survey of the land described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management--Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  5. 75 FR 54910 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2010-09-09

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia, 30... of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153. Attn...

  6. Petrologically-constrained thermo-chemical modelling of cratonic upper mantle consistent with elevation, geoid, surface heat flow, seismic surface waves and MT data

    Science.gov (United States)

    Jones, A. G.; Afonso, J. C.

    2015-12-01

    The Earth comprises a single physio-chemical system that we interrogate from its surface and/or from space making observations related to various physical and chemical parameters. A change in one of those parameters affects many of the others; for example a change in velocity is almost always indicative of a concomitant change in density, which results in changes to elevation, gravity and geoid observations. Similarly, a change in oxide chemistry affects almost all physical parameters to a greater or lesser extent. We have now developed sophisticated tools to model/invert data in our individual disciplines to such an extent that we are obtaining high resolution, robust models from our datasets. However, in the vast majority of cases the different datasets are modelled/inverted independently of each other, and often even without considering other data in a qualitative sense. The LitMod framework of Afonso and colleagues presents integrated inversion of geoscientific data to yield thermo-chemical models that are petrologically consistent and constrained. Input data can comprise any combination of elevation, geoid, surface heat flow, seismic surface wave (Rayleigh and Love) data and receiver function data, and MT data. The basis of LitMod is characterization of the upper mantle in terms of five oxides in the CFMAS system and a thermal structure that is conductive to the LAB and convective along the adiabat below the LAB to the 410 km discontinuity. Candidate solutions are chosen from prior distributions of the oxides. For the crust, candidate solutions are chosen from distributions of crustal layering, velocity and density parameters. Those candidate solutions that fit the data within prescribed error limits are kept, and are used to establish broad posterior distributions from which new candidate solutions are chosen. Examples will be shown of application of this approach fitting data from the Kaapvaal Craton in South Africa and the Rae Craton in northern Canada. I

  7. 78 FR 70573 - Eastern States: Filing of Plats of Survey

    Science.gov (United States)

    2013-11-26

    ... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLES956000 L14200000.BJ0000 14X] Eastern... BLM-Eastern States office in Springfield, Virginia, 30 calendar days from the date of publication in the Federal Register. FOR FURTHER INFORMATION CONTACT: Bureau of Land Management-Eastern States, 7450...

  8. 75 FR 39579 - Eastern States: Filing of Plats of Survey

    Science.gov (United States)

    2010-07-09

    ...] Eastern States: Filing of Plats of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... file the plats of survey of the lands described below in the BLM-Eastern States office in Springfield... CONTACT: Bureau of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153...

  9. 75 FR 18234 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2010-04-09

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of...) will file the plats of survey of the lands described below in the BLM-Eastern States office in... INFORMATION CONTACT: Bureau of Land Management--Eastern States, 7450 Boston Boulevard, Springfield, Virginia...

  10. 75 FR 13302 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2010-03-19

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of...) will file the plat of survey of the lands described below in the BLM-Eastern States office in... INFORMATION CONTACT: Bureau of Land Management--Eastern States, 7450 Boston Boulevard, Springfield, Virginia...

  11. 77 FR 63856 - Eastern States: Filing of Plats of Survey

    Science.gov (United States)

    2012-10-17

    ...] Eastern States: Filing of Plats of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... plats of survey of the lands described below in the BLM-Eastern States office in Springfield, Virginia... CONTACT: Bureau of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153...

  12. 78 FR 23952 - Eastern States: Filing of Plats of Survey

    Science.gov (United States)

    2013-04-23

    ...] Eastern States: Filing of Plats of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... file the plats of survey of the lands described below in the BLM-Eastern States office in Springfield... CONTACT: Bureau of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153...

  13. 76 FR 45292 - Eastern States: Filing of Plats of Survey

    Science.gov (United States)

    2011-07-28

    ...] Eastern States: Filing of Plats of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... the plats of survey of the lands described below in the BLM-Eastern States office in Springfield... CONTACT: Bureau of Land Management--Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153...

  14. 76 FR 38381 - Texas Eastern Transmission, LP; Notice of Amendment

    Science.gov (United States)

    2011-06-30

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP11-67-001] Texas Eastern Transmission, LP; Notice of Amendment Take notice that on June 13, 2011, Texas Eastern Transmission, LP (Texas Eastern), 5400 Westheimer Court, Houston, Texas 77056, filed in the above referenced docket an amendment...

  15. 77 FR 20015 - Texas Eastern Transmission, LP; Notice of Application

    Science.gov (United States)

    2012-04-03

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP12-88-000] Texas Eastern Transmission, LP; Notice of Application Take notice that on March 19, 2012, Texas Eastern Transmission, LP (Texas Eastern), 5400 Westheimer Court, Houston, Texas 77056-5310, filed an application in Docket No...

  16. 75 FR 4412 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2010-01-27

    ...] Eastern States: Filing of Plat of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... file the plat of survey of the lands described below in the BLM-Eastern States office in Springfield... CONTACT: Bureau of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia 22153...

  17. 77 FR 12045 - Texas Eastern Transmission, LP; Notice of Application

    Science.gov (United States)

    2012-02-28

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP12-68-000] Texas Eastern Transmission, LP; Notice of Application Take notice that on February 16, 2012, Texas Eastern Transmission, LP (Texas Eastern), PO Box 1642, Houston, Texas 77056 filed an application in the above referenced docket...

  18. The energy question in Eastern Europe

    International Nuclear Information System (INIS)

    Locatelli, C.

    1992-01-01

    In a first part, this book describes the energetic schemes, energy consumption and centralized economy in Eastern Europe countries. In the second part, the relationships between energy supply and macro-economic disequilibria in USSR is studied: Petroleum and power generation are chosen as example. In the third part, the book shows the energetic stakes in Central and Eastern Europe: the end of the exchange model (imports, exports) and the energetic schemes facing economical reforms

  19. Midwifery education in Central-Eastern Europe.

    Science.gov (United States)

    Mivšek, Polona; Baškova, Martina; Wilhelmova, Radka

    2016-02-01

    Problems in midwifery in many Central-Eastern European countries are very similar; it is possible to speak about the evolving Central-Eastern model of midwifery care. The educational models of this region have a relatively strong theoretical part; however, there is an insufficient practical dimension. Theoretical part of midwifery education in the universities is relatively autonomous and is slowly changing the professional identity of graduates. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Foggy Diaspora: Romanian Women in Eastern Serbia

    Directory of Open Access Journals (Sweden)

    Sorescu-Marinković Annemarie

    2016-06-01

    Full Text Available Drawing on ethnographic and anthropological research on the Romanian communities in Eastern Serbia, this article seeks to contribute to the global scholarship on diaspora and migration. It reveals interesting differences between the well defined and intensely studied notion of “diaspora” on the one hand, and the understudied, but useful concept of “near diaspora” on the other. First, the presence of Romanians in Eastern Serbia is looked at from a gender perspective, in the wider context of feminization of international migration. Second, the paper argues that the Romanian women in Eastern Serbia adopt the strategy of living in the “social fog”, thus becoming what can be termed “foggy diaspora”.

  1. 78 FR 66352 - Texas Eastern Transmission, LP; Notice of Application

    Science.gov (United States)

    2013-11-05

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP14-9-000] Texas Eastern Transmission, LP; Notice of Application Take notice that on October 17, 2013, Texas Eastern Transmission, LP (Texas Eastern), 5400 Westheimer Court, Houston, Texas 77056, filed an application in Docket No. CP14-9...

  2. 75 FR 72837 - Eastern States: Filing of Plats of Survey

    Science.gov (United States)

    2010-11-26

    ...] Eastern States: Filing of Plats of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... (BLM) will file the plats of survey of the lands described below in the BLM-Eastern States office in... INFORMATION CONTACT: Bureau of Land Management-Eastern States, 7450 Boston Boulevard, Springfield, Virginia...

  3. 76 FR 3651 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2011-01-20

    ... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLES956000-L14200000-BJ0000] Eastern States... described below in the BLM-Eastern States office in Springfield, Virginia, 30 calendar days from the date of publication in the Federal Register. FOR FURTHER INFORMATION CONTACT: Bureau of Land Management-Eastern States...

  4. 78 FR 16294 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2013-03-14

    ... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLES956000-L14100000-BX0000] Eastern States... of Land Management (BLM) will file the plat of survey of the lands described below in the BLM-Eastern... Register. FOR FURTHER INFORMATION CONTACT: Bureau of Land Management-Eastern States, 7450 Boston Boulevard...

  5. 77 FR 37919 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2012-06-25

    ... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLES956000-L19100000-Bk0000] Eastern States... of Land Management (BLM) will file the plat of survey of the lands described below in the BLM-Eastern... Register. FOR FURTHER INFORMATION CONTACT: Bureau of Land Management-Eastern States, 7450 Boston Boulevard...

  6. 76 FR 2133 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2011-01-12

    ... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLES956000-L14200000-BJ0000] Eastern States... described below in the BLM-Eastern States office in Springfield, Virginia, 30 calendar days from the date of publication in the Federal Register. FOR FURTHER INFORMATION CONTACT: Bureau of Land Management-Eastern States...

  7. 76 FR 26767 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2011-05-09

    ... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLES956000-L14200000-BJ0000] Eastern States... described below in the BLM-Eastern States office in Springfield, Virginia, 30 calendar days from the date of publication in the Federal Register. FOR FURTHER INFORMATION CONTACT: Bureau of Land Management-Eastern States...

  8. 78 FR 79687 - Texas Eastern Transmission, LP; Notice of Application

    Science.gov (United States)

    2013-12-31

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP14-29-000] Texas Eastern Transmission, LP; Notice of Application Take notice that on December 10, 2013 Texas Eastern Transmission, LP (Texas Eastern), at 5400 Westheimer Court, Houston, Texas 77056, filed an application in Docket No. CP14...

  9. 77 FR 26534 - Texas Eastern Transmission, LP; Notice of Application

    Science.gov (United States)

    2012-05-04

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP12-164-000] Texas Eastern Transmission, LP; Notice of Application Take notice that on April 19, 2012, Texas Eastern Transmission, LP (Texas Eastern), 5400 Westheimer Court, Houston, Texas 77056, filed in Docket No. CP12-164-000, a request...

  10. Vitamin D deficiency is endemic in Middle Eastern sportsmen.

    Science.gov (United States)

    Hamilton, Bruce; Grantham, Justin; Racinais, Sebastien; Chalabi, Hakim

    2010-10-01

    While vitamin D deficiency is well recognized in Middle Eastern women as a result of cultural norms of remaining covered, Middle Eastern men are an under-reported group. Vitamin D is now known to have multiple effects, including an impact on muscle function, thereby increasing the relevance for sportsmen. The aim of the present study was to evaluate serum 25-hydroxyvitamin D (25(OH)D) levels in young male Middle Eastern athletes. Cross-sectional study. Qatar Orthopaedic and Sports Medicine Hospital, Doha, Qatar. Ninety-three Middle Eastern men presenting to hospital for an annual screening undertook a blood test to evaluate their vitamin D status. Ninety-one per cent of athletes were found to be deficient in 25(OH)D (serum concentration Middle Eastern male athletes. Given the potentially significant long- and short-term effects of 25(OH)D deficiency, serum 25(OH)D evaluation should be part of the routine assessment in this region.

  11. Discrepancy of cytogenetic analysis in Western and eastern Taiwan.

    Science.gov (United States)

    Chang, Yu-Hsun; Chen, Pui-Yi; Li, Tzu-Ying; Yeh, Chung-Nan; Li, Yi-Shian; Chu, Shao-Yin; Lee, Ming-Liang

    2013-06-01

    This study aimed at investigating the results of second-trimester amniocyte karyotyping in western and eastern Taiwan, and identifying any regional differences in the prevalence of fetal chromosomal anomalies. From 2004 to 2009, pregnant women who underwent amniocentesis in their second trimester at three hospitals in western Taiwan and at four hospitals in eastern Taiwan were included. All the cytogenetic analyses of cultured amniocytes were performed in the cytogenetics laboratory of the Genetic Counseling Center of Hualien Buddhist Tzu Chi General Hospital. We used the chi-square test, Student t test, and Mann-Whitney U test to evaluate the variants of clinical indications, amniocyte karyotyping results, and prevalence and types of chromosomal anomalies in western and eastern Taiwan. During the study period, 3573 samples, 1990 (55.7%) from western Taiwan and 1583 (44.3%) from eastern Taiwan, were collected and analyzed. The main indication for amniocyte karyotyping was advanced maternal age (69.0% in western Taiwan, 67.1% in eastern Taiwan). The detection rates of chromosomal anomalies by amniocyte karyotyping in eastern Taiwan (45/1582, 2.8%) did not differ significantly from that in western Taiwan (42/1989, 2.1%) (p = 1.58). Mothers who had abnormal ultrasound findings and histories of familial hereditary diseases or chromosomal anomalies had higher detection rates of chromosomal anomalies (9.3% and 7.2%, respectively). The detection rate of autosomal anomalies was higher in eastern Taiwan (93.3% vs. 78.6%, p = 0.046), but the detection rate of sex-linked chromosomal anomalies was higher in western Taiwan (21.4% vs. 6.7%, p = 0.046). We demonstrated regional differences in second-trimester amniocyte karyotyping results and established a database of common chromosomal anomalies that could be useful for genetic counseling, especially in eastern Taiwan. Copyright © 2012. Published by Elsevier B.V.

  12. 76 FR 16444 - Eastern States: Filing of Plat of Survey

    Science.gov (United States)

    2011-03-23

    ... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLES956000-L14200000-BJ0000] Eastern States... described below in the BLM-Eastern States office in Springfield, Virginia. DATES: BLM will file the plat of survey on April 22, 2011. FOR FURTHER INFORMATION CONTACT: Bureau of Land Management-Eastern States, 7450...

  13. 76 FR 33342 - Eastern States; Filing of Plats of Survey

    Science.gov (United States)

    2011-06-08

    ...] Eastern States; Filing of Plats of Survey AGENCY: Bureau of Land Management, Interior. ACTION: Notice of... published in the Federal Register, Volume 75, Number 174, on page 54910 a notice entitled ``Eastern States..., 2011 and the plat of survey accepted June 22, 2010, was officially filed in Eastern States Office...

  14. 75 FR 45611 - Texas Eastern Transmission LP; Notice of Application

    Science.gov (United States)

    2010-08-03

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP10-471-000] Texas Eastern Transmission LP; Notice of Application July 27, 2010. Take notice that on July 15, 2010, Texas Eastern Transmission (Texas Eastern), P.O. Box 1642, Houston, Texas 77251-1642, filed in Docket No. CP10-471-000, an...

  15. 78 FR 54482 - Eastern States: Filing of Plats of Survey

    Science.gov (United States)

    2013-09-04

    ... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLES956000-L14200000-BK0000] Eastern States... the Federal Register, Volume 78, Number 2, on pages 318-319 a notice entitled ``Eastern States: Filing... resurvey of a portion of the Qualla Indian Boundary, land held in trust for the Eastern Band of Cherokee...

  16. 77 FR 54557 - Eastern Idaho Resource Advisory Committee

    Science.gov (United States)

    2012-09-05

    ... DEPARTMENT OF AGRICULTURE Forest Service Eastern Idaho Resource Advisory Committee AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Easern Idaho Resource Advisory Committee will meet... between 8 a.m. and 8 p.m., Eastern Standard Time, Monday through Friday. SUPPLEMENTARY INFORMATION: The...

  17. Middle Eastern Christian spaces in Europe

    DEFF Research Database (Denmark)

    Galal, Lise Paulsen; Hunter, Alistair; McCallum, Fiona

    2016-01-01

    Despite little scholarly attention, Middle Eastern Christian Churches are a well-established element of the European religious landscape. Based on collaborative research, this article examines how three mutual field visits facilitated a deeper understanding of the complexity that characterises...... church establishment and activities among Iraqi, Assyrian/Syriac and Coptic Orthodox Christians in the UK, Sweden and Denmark. Exploring analytical dimensions of space, diversity, size, and minority position we identify three positions of Middle Eastern Christians: in London as the epitome of super...

  18. Eastern Africa Social Science Research Review: About this journal

    African Journals Online (AJOL)

    Eastern Africa Social Science Research Review: About this journal. Journal Home > Eastern Africa Social Science Research Review: About this journal. Log in or Register to get access to full text downloads.

  19. Issues in Health Care of Middle Eastern Patients

    Science.gov (United States)

    Lipson, Juliene G.; Meleis, Afaf I.

    1983-01-01

    Relationships between Middle Eastern patients and Western health care professionals are often troubled by mutual misunderstanding of culturally influenced values and communication styles. Although Middle Easterners vary ethnically, they do share a core of common values and behavior that include the importance of affiliation and family, time and space orientations, interactional style and attitudes toward health and illness. Problems in providing health care involve obtaining adequate information, “demanding behavior” by a patient's family, conflicting beliefs about planning ahead and differing patterns of communicating grave diagnoses or “bad news.” There are guidelines that will provide an understanding of the cultural characteristics of Middle Easterners and, therefore, will improve rather than impede their health care. A personal approach and continuity of care by the same health care professional help to bridge the gap between Middle Eastern cultures and Western medical culture. In addition, periodic use of cultural interpreters helps ameliorate the intensity of some cultural issues. PMID:6364575

  20. A study of the hydrothermal alteration in Paleoproterozoic volcanic centers, São Félix do Xingu region, Amazonian Craton, Brazil, using short-wave infrared spectroscopy

    Science.gov (United States)

    da Cruz, Raquel Souza; Fernandes, Carlos Marcello Dias; Villas, Raimundo Netuno Nobre; Juliani, Caetano; Monteiro, Lena Virgínia Soares; de Almeida, Teodoro Isnard Ribeiro; Lagler, Bruno; de Carvalho Carneiro, Cleyton; Misas, Carlos Mario Echeverri

    2015-10-01

    Hypogene hydrothermal minerals have been identified by short-wave infrared spectroscopy in hydrothermally altered rocks from the Sobreiro and Santa Rosa formations, which belong to a Paleoproterozoic volcano-plutonic system in Amazonian craton. Three clay minerals are spectrally recognized: montmorillonite, kaolinite, and illite. The integration of these data with those available in the literature, including gold occurrences, suggests that those rocks are hydrothermal products of both volcanic thermal sources and later crustal intrusions, as evidenced by variable styles of propylitic, sericitic, potassic, and intermediate argillic alteration. The influence of meteoric fluids is emphasized. This low cost exploratory technique, which can be applied to hand samples, seems to be promising in the separation of hydrothermally altered volcano-plutonic centers in regions submitted to severe weathering conditions, in addition to aid elaborating models for prospecting mineral deposits.

  1. Long-term landscape evolution of the South Atlantic "passive" continental margin in Eastern Argentina using apatite fission-track thermochronology

    Science.gov (United States)

    Pfister, Sabrina; Kollenz, Sebastian; Glasmacher, Ulrich A.

    2015-04-01

    To understand the evolution of the "passive" continental margin in Argentina low temperature thermochronology is an appropriate method, which might lead to new insights in this area. The Tandilia System, also called Sierras Septentrionales, is located south of the Río de la Plato Craton in eastern Argentina in the state of Buenos Aires. North of the hills the Salado basin is located whereas the Claromecó basin is situated south of the mountain range. In contrary to most basins along the South American "passive" continental margin, the Tandilia-System and the neighbouring basins trend perpendicular to the coast line. The topography is fairly flat with altitudes up to 350 m. The igneous-metamorphic basement is pre-Proterozoic in age and build up of mainly granitic-tonalitic gneisses, migmatites, amphibolites, some ultramafic rocks and granitoid plutons. It is overlain by a series of Neoproterozoic to early Paleozoic sedimentary rocks (Cingolani 2011), like siliciclastic rocks, dolostones, shales and limestones (Demoulin 2005). The aim of the study is to quantify the long-term landscape evolution of the "passive" continental margin in eastern Argentina in terms of thermal, exhumation and tectonic evolution. For that purpose, samples were taken from the basement of the Sierra Septentrionales and analyzed with the apatite fission-track method. Further 2-D thermokinematic modeling was conducted with the computer code HeFTy (Ketcham 2005; Ketcham 2007; Ketcham et al. 2009). Because there are different hypotheses in literature regarding the geological evolution of this area two different models were generated, one after Demoulin et al. (2005) and another after Zalba et al.(2007). All samples were taken from the Neoproterozoic igneous-metamorphic basement. Apatite fission-track ages range from 101.6 (9.4) to 228.9 (22.3) Ma, and, therefore, are younger than their formation age, indicating all samples have been thermally reset. Six samples accomplished enough confined

  2. Molecular phylogenetic analysis of Fasciola flukes from eastern India.

    Science.gov (United States)

    Hayashi, Kei; Ichikawa-Seki, Madoka; Mohanta, Uday Kumar; Singh, T Shantikumar; Shoriki, Takuya; Sugiyama, Hiromu; Itagaki, Tadashi

    2015-10-01

    Fasciola flukes from eastern India were characterized on the basis of spermatogenesis status and nuclear ITS1. Both Fasciola gigantica and aspermic Fasciola flukes were detected in Imphal, Kohima, and Gantoku districts. The sequences of mitochondrial nad1 were analyzed to infer their phylogenetical relationship with neighboring countries. The haplotypes of aspermic Fasciola flukes were identical or showed a single nucleotide substitution compared to those from populations in the neighboring countries, corroborating the previous reports that categorized them in the same lineage. However, the prevalence of aspermic Fasciola flukes in eastern India was lower than those in the neighboring countries, suggesting that they have not dispersed throughout eastern India. In contrast, F. gigantica was predominant and well diversified, and the species was thought to be distributed in the area for a longer time than the aspermic Fasciola flukes. Fasciola gigantica populations from eastern India were categorized into two distinct haplogroups A and B. The level of their genetic diversity suggests that populations belonging to haplogroup A have dispersed from the west side of the Indian subcontinent to eastern India with the artificial movement of domestic cattle, Bos indicus, whereas populations belonging to haplogroup B might have spread from Myanmar to eastern India with domestic buffaloes, Bubalus bubalis. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  3. 78 FR 15797 - Eastern Band of Cherokee Indians Disaster #NC-00049

    Science.gov (United States)

    2013-03-12

    ... SMALL BUSINESS ADMINISTRATION [Disaster Declaration 13513 and 13514] Eastern Band of Cherokee... Notice of the Presidential declaration of a major disaster for Public Assistance Only for the Eastern... adversely affected by the disaster: Primary Areas: Eastern Band of Cherokee Indians and Associated Lands...

  4. Contribution on the Northeastern Minas Gerais geologic-geochronologic study, Brazil

    International Nuclear Information System (INIS)

    Siga Junior, O.; Cordani, U.G.; Basei, M.A.S.; Teixeira, W.; Kawashita, K.

    1987-01-01

    This work demonstrates the potential of integrated Rb-Sr, K-Ar, and U-Pb determinations, when applied to basic regional geology. The different interpretative values of these methodologies contribute to the understanding of the tectonic processes developed in the south-eastern border of the Sao Francisco Craton (northeastern Minas Gerais). The Brazilian Orogenic Cycle is characterized in the area by the Salinas metasediments and the gneissic-migmatitic rocks of the eastern sector. Rb-Sr and U-Pb data indicate the generation of most or even all of these rocks in the 660-570 Ma, interval. No indications of ancient terrains were obtained, and previous ideas of a pervasive reworking of an Archean or Lower Proterozoic crust must be discarded. The K-Ar analyses indicate a crustal level in which temperature remained above 250 O C until at least 480 Ma. (author)

  5. Introduction to Eastern Philosophy, Social Studies: 6414.23.

    Science.gov (United States)

    Payne, Judy Reeder

    Major Eastern philosophies and/or religions consisting of Hinduism, Buddhism, Confucianism, Taoism, and Shintoism are investigated by 10th through 12th grade students in this general social studies quinmester course. Since Eastern philosophical ideas are already influencing students, this course aims to guide students in a universal search for…

  6. 78 FR 39719 - Eastern Shore Natural Gas Company; Notice of Application

    Science.gov (United States)

    2013-07-02

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [ Docket No. CP13-498-000] Eastern Shore Natural Gas Company; Notice of Application Take notice that on June 13, 2013, Eastern Shore Natural Gas Company (Eastern Shore) filed with the Federal Energy Regulatory Commission an application under section 7...

  7. 77 FR 67021 - Eastern States: Filing of Plat of Survey; Maine

    Science.gov (United States)

    2012-11-08

    ...] Eastern States: Filing of Plat of Survey; Maine AGENCY: Bureau of Land Management, Interior. ACTION... below in the BLM-Eastern States office in Springfield, Virginia, 30 calendar days from the date of publication in the Federal Register. FOR FURTHER INFORMATION CONTACT: Bureau of Land Management--Eastern...

  8. 77 FR 65542 - Eastern Shore Natural Gas Company; Notice of Application

    Science.gov (United States)

    2012-10-29

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP13-6-000] Eastern Shore Natural Gas Company; Notice of Application Take notice that on October 12, 2012, Eastern Shore Natural Gas Company (Eastern Shore), 1110 Forrest Avenue, Dover, Delaware 19904, filed in the above referenced docket...

  9. 78 FR 26652 - Eastern States: Filing of Plat of Survey; Mississippi

    Science.gov (United States)

    2013-05-07

    ... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLES956000 .L1420] Eastern States: Filing of...-Eastern States office in Springfield, Virginia, 30 calendar days from the date of publication in the Federal Register. FOR FURTHER INFORMATION CONTACT: Bureau of Land Management-Eastern States, 7450 Boston...

  10. 77 FR 22773 - Texas Eastern Transmission, L.P.; Notice of Response

    Science.gov (United States)

    2012-04-17

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [ Docket No. RP12-318-001] Texas Eastern... order of the Federal Energy Regulatory Commission in the above- captioned proceeding Texas Eastern Transmission, LP (Texas Eastern) submits its response to show cause why it should not be required to file...

  11. 78 FR 16293 - Eastern States: Filing of Plat of Survey; Mississippi

    Science.gov (United States)

    2013-03-14

    ...] Eastern States: Filing of Plat of Survey; Mississippi AGENCY: Bureau of Land Management, Interior. ACTION... below in the BLM-Eastern States office in Springfield, Virginia, 30 calendar days from the date of publication in the Federal Register. FOR FURTHER INFORMATION CONTACT: Bureau of Land Management-Eastern States...

  12. 75 FR 13524 - Eastern Shore Natural Gas Company; Notice of Application

    Science.gov (United States)

    2010-03-22

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP10-76-000] Eastern Shore Natural Gas Company; Notice of Application March 15, 2010. Take notice that on March 5, 2010, Eastern Shore Natural Gas Company, (Eastern Shore), 1110 Forrest Avenue, Dover, Delaware 19904, pursuant to...

  13. Uterine prolapse prevention in Eastern Nepal

    DEFF Research Database (Denmark)

    Radl, Christina Mathilde; Rajwar, Ranjita; Aro, Arja R.

    2012-01-01

    are working well or the attitudes toward them. This paper presents the findings of a qualitative study on primary and secondary prevention of uterine prolapse in Eastern Nepal. Method: The study involved eight focus group discussions with 71 women in six villages of the eastern districts of Siraha and Saptari......: It was found that patriarchy, gender discrimination, and cultural traditions such as early marriage and pregnancy make it difficult for people to discontinue uterine prolapse risk behaviors. Women are aware of risk factors, prevention, and treatment, but are powerless to change their situations. Health...

  14. Fission track geochronology of Eastern Ghats

    Energy Technology Data Exchange (ETDEWEB)

    Virk, H S; Koul, S L; Singh, S [Punjabi Univ., Patiala (India). Dept. of Physics

    1978-12-01

    Fission track geochronology of Eastern Ghats has been established by using fission track technique in dating micaceous and accessory minerals occurring in the region. Annealing studies confirm that radiation damage fossil tracks can be erased in minerals under intense metamorphic episodes thus resetting the geological clock. The fission track ages of the minerals range between 450 +- 5 m.y. to 622 +- 148 m.y. It is concluded that f.t. ages of the minerals date the last metamorphic event of the Eastern Ghats, known as the Indian Ocean Cycle.

  15. Tectonics of the Qinling (Central China): Tectonostratigraphy, geochronology, and deformation history

    Science.gov (United States)

    Ratschbacher, L.; Hacker, B.R.; Calvert, A.; Webb, L.E.; Grimmer, J.C.; McWilliams, M.O.; Ireland, T.; Dong, S.; Hu, Jiawen

    2003-01-01

    The Qinling orogen preserves a record of late mid-Proterozoic to Cenozoic tectonism in central China. High-pressure metamorphism and ophiolite emplacement (Songshugou ophiolite) assembled the Yangtze craton, including the lower Qinling unit, into Rodinia during the ~1.0 Ga Grenvillian orogeny. The lower Qinling unit then rifted from the Yangtze craton at ~0.7 Ga. Subsequent intra-oceanic arc formation at ~470-490 Ma was followed by accretion of the lower Qinling unit first to the intra-oceanic arc and then to the Sino-Korea craton. Subduction then imprinted a ~400 Ma Andean-type magmatic arc onto all units north of the northern Liuling unit. Oblique subduction created Silurian-Devonian WNW-trending, sinistral transpressive wrench zones (e.g., Lo-Nan, Shang-Dan), and Late Permian-Early Triassic subduction reactivated them in dextral transpression (Lo-Nan, Shang-Xiang, Shang-Dan) and subducted the northern edge of the Yangtze craton. Exhumation of the cratonal edge formed the Wudang metamorphic core complex during dominantly pure shear crustal extension at ~230-235 Ma. Post-collisional south-directed shortening continued through the Early Jurassic. Cretaceous reactivation of the Qinling orogen started with NW-SE sinistral transtension, coeval with large-scale Early Cretaceous crustal extension and sinistral transtension in the northern Dabie Shan; it presumably resulted from the combined effects of the Siberia-Mongolia-Sino-Korean and Lhasa-West Burma-Qiangtang-Indochina collisions and Pacific subduction. Regional dextral wrenching was active within a NE-SW extensional regime between ~60 and 100 Ma. An Early Cretaceous Andean-type continental magmatic arc, with widespread Early Cretaceous magmatism and back-arc extension, was overprinted by shortening related to the collision of Yangtze-Indochina Block with the West Philippines Block. Strike-slip and normal faults associated with Eocene half-graben basins record Paleogene NNE-SSW contraction and WNW-ESE extension

  16. 76 FR 14387 - Texas Eastern Transmission, LP; Notice of Request Under Blanket Authorization

    Science.gov (United States)

    2011-03-16

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP11-118-000] Texas Eastern... Eastern Transmission, LP (Texas Eastern), Post Office Box 1642, Houston, Texas 77251-1642, filed in Docket... West Cameron Blocks 566, 565, and 548, offshore Louisiana, under Texas Eastern's blanket certificate...

  17. Republic of Moldova – the success story of the Eastern Partnership

    Directory of Open Access Journals (Sweden)

    Vasile Rotaru

    2012-02-01

    Full Text Available The power change in Ukraine and the violent crackdown on the post electoral protestors in Belarus jeopardize the Eastern Partnership. The EU’s efforts to democratize and stabilize its eastern border could become more and more difficult if Brussels does not find quickly a solution to keep the six partners interested in its projects. This paper examines the latest challenges of the Eastern Partnership and the reasons why the Republic of Moldova could be the successful story the Eastern Partnership is seeking.

  18. Geophysical constraints on the mantle structure of the Canadian Cordillera and North America Craton

    Science.gov (United States)

    Yu, T. C.; Currie, C. A.; Unsworth, M. J.

    2017-12-01

    In western Canada, geophysical data indicate that there is a pronounced contrast in mantle structure between the Canadian Cordillera (CC) and North America craton (NAC). The CC is characterized by lower mantle seismic velocity, higher surface heat flow, lower mantle electrical resistivity and lower effective elastic thickness. These observations are consistent with two distinct thermal regimes: the CC has hot and thin lithosphere, while the NAC lithosphere is cool and thick. The boundary between the CC and NAC coincides with the south-north trending Rocky Mountain Trench - Tintina Fault system. Earlier studies have hypothesized that the thin CC lithosphere is maintained by small-scale convection of hydrated mantle, whereas the NAC lithosphere is dry and resistant to thinning. Here, we test this hypothesis through a detailed examination of two independent data sets: (1) seismic shear-wave (Vs) tomography models and (2) magnetotelluric (MT) measurements of mantle electrical resistivity. We analyze tomography model NA07 at 50-250 km depth and create a mapping of Vs to temperature based on mantle composition (via Perple_X) and a correction for anelasticity. For the CC, the calculated temperature is relatively insensitive to mantle composition but strongly depends on the water content and anelastic correction. With a laboratory-based correction, the estimated temperature is 1150 °C at 100 km depth for wet mantle, compared to 1310 °C for dry mantle; no melt is predicted in either case. An empirical anelastic correction predicts a 115 °C hotter mantle and likely some melt. In contrast, composition is the main control on the calculated temperature for the NAC, especially at depths electrical resistivity is sensitive to mantle temperature and hydration.

  19. Nuclear power in Eastern Europe

    International Nuclear Information System (INIS)

    Sturm, R.

    1993-01-01

    This paper analyses the operating experience of nuclear power plants in Eastern and Western Europe, the former Soviet Union and the United States to investigate differences in the effects of learning, technical change and the effect of recent political developments. The performance of Soviet-designed reactors compares favourably with Western reactors on the standard performance measures. However, learning curve estimates reveal a disturbing trend: the former Soviet Union and all countries in Eastern Europe experience increasing unplanned losses as plants age, whereas all Western countries reduce their unplanned losses. A similar ''forgetting'' phenomenon is observable for plant availability and there is some evidence that the recent political and economic reorganization have exacerbated this trend. (Author)

  20. Precambrian large igneous provinces: an overview of geochronology, origins and impact on earth evolution

    International Nuclear Information System (INIS)

    Heaman, Larry M.

    2008-01-01

    Precambrian large igneous provinces flourished during the Proterozoic and some, such as the 1.27 Ga Mackenzie event in North America, resemble their Phanerozoic counterparts with good evidence for the production of large volumes of mafic magma in short periods of geologic time (<10 m.y.), a specific focus of this magmatism, and regional uplift prior to the onset of volcanism. In many Precambrian examples, the flood basalts have been largely removed by erosion and only the root zone (e.g. dyke swarm, layered mafic intrusion) of these large igneous provinces is preserved. The short duration of this magmatism and the geometric relationship between linear dyke swarms and basement geology can potentially provide a robust geological pin in continental reconstructions. The extensive 2.37 Ga E-W trending Bangalore dyke swarm in the Dharwar craton, India cross-cuts N-S trending Neoarchean greenstone belts and the 2.51 Ga Closepet granite and is a good example of the potential for providing a cornerstone in Paleoproterozoic continent reconstruction. In contrast, the 1.89 Ga Southern Bastar-Cuddapah large igneous province in southern India is one of several large igneous provinces formed at this time on different continents, including the 1.89-1.88 Ga circum-Superior mafic/ultramafic magmatism in North America and the 1.88-1.87 Ga Waterberg Group sills in South Africa, and is part of a global period of enhanced mantle melting. A challenge for future attempts at Precambrian continent reconstruction is to distinguish between discrete global periods of enhanced mantle melting and a single specific focus large igneous province. (author)

  1. Religions in South-Eastern Europe: The Historico-Anthropological Approach

    Directory of Open Access Journals (Sweden)

    Michael Mitterauer

    2008-06-01

    Full Text Available The article approaches religious phenomena in South-Eastern Europe in a historico-anthropological manner. With the aid of historical comparison, the author tries to throw light on the religious phenomena of South-Eastern Europe and to present them in a lucid review. A significant place in this process is given to historical sociology as a discipline which, among other, also deals with the religious conditioning of social processes. The text consists of two parts. In the first, the author deals with the question of the religious particularity of South-Eastern Europe and considers it from several viewpoints. The author regards the most important features of the religious situation in that part of Europe as being particularism, archaicism and syncretism. He analyses the historical conditioning of the viability of the three monotheistic world religions in the region, their influence on the social development of South-Eastern Europe, the stance of the authorities towards religious communities and the existence of diverse traditions within individual religious cultures. Along with analysis of the presence of ancient elements and the continuity of pre-Christian rituals and beliefs, the author also stresses the strong syncretism marking the religious traditions of South-Eastern Europe. In the second part of the text the author compares religious phenomena in South-Eastern Europe and analyses regional religious traditions. He presents from the historico-anthropological aspect the religious rituals, the bearers of rituals, the place and time of rituals and the ritual languages of each of the world religions represented in the region. Emphasising the continuity of religious life and religious traditions in South-Eastern Europe, the author ends with the period of Communist rule in the second half of the 20th century, and deliberation that Communism, too, with its atheist doctrine in the secular form of cult, in fact carried on from religious tradition.

  2. Ungulate predation and ecological roles of wolves and coyotes in eastern North America.

    Science.gov (United States)

    Benson, John F; Loveless, Karen M; Rutledge, Linda Y; Patterson, Brent R

    2017-04-01

    Understanding the ecological roles of species that influence ecosystem processes is a central goal of ecology and conservation biology. Eastern coyotes (Canis latrans) have ascended to the role of apex predator across much of eastern North America since the extirpation of wolves (Canis spp.) and there has been considerable confusion regarding their ability to prey on ungulates and their ecological niche relative to wolves. Eastern wolves (C. lycaon) are thought to have been the historical top predator in eastern deciduous forests and have previously been characterized as deer specialists that are inefficient predators of moose because of their smaller size relative to gray wolves (C. lupus). We investigated intrinsic and extrinsic influences on per capita kill rates of white-tailed deer (Odocoileus virginianus) and moose (Alces alces) during winter by sympatric packs of eastern coyotes, eastern wolves, and admixed canids in Ontario, Canada to clarify the predatory ability and ecological roles of the different canid top predators of eastern North America. Eastern coyote ancestry within packs negatively influenced per capita total ungulate (deer and moose combined) and moose kill rates. Furthermore, canids in packs dominated by eastern coyote ancestry consumed significantly less ungulate biomass and more anthropogenic food than packs dominated by wolf ancestry. Similar to gray wolves in previous studies, eastern wolves preyed on deer where they were available. However, in areas were deer were scarce, eastern wolves killed moose at rates similar to those previously documented for gray wolves at comparable moose densities across North America. Eastern coyotes are effective deer predators, but their dietary flexibility and low kill rates on moose suggest they have not replaced the ecological role of wolves in eastern North America. © 2017 by the Ecological Society of America.

  3. Ozone and carbon monoxide budgets over the Eastern Mediterranean.

    Science.gov (United States)

    Myriokefalitakis, S; Daskalakis, N; Fanourgakis, G S; Voulgarakis, A; Krol, M C; Aan de Brugh, J M J; Kanakidou, M

    2016-09-01

    The importance of the long-range transport (LRT) on O3 and CO budgets over the Eastern Mediterranean has been investigated using the state-of-the-art 3-dimensional global chemistry-transport model TM4-ECPL. A 3-D budget analysis has been performed separating the Eastern from the Western basins and the boundary layer (BL) from the free troposphere (FT). The FT of the Eastern Mediterranean is shown to be a strong receptor of polluted air masses from the Western Mediterranean, and the most important source of polluted air masses for the Eastern Mediterranean BL, with about 40% of O3 and of CO in the BL to be transported from the FT aloft. Regional anthropogenic sources are found to have relatively small impact on regional air quality in the area, contributing by about 8% and 18% to surface levels of O3 and CO, respectively. Projections using anthropogenic emissions for the year 2050 but neglecting climate change calculate a surface O3 decrease of about 11% together with a surface CO increase of roughly 10% in the Eastern Mediterranean. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Dust-wind interactions can intensify aerosol pollution over eastern China.

    Science.gov (United States)

    Yang, Yang; Russell, Lynn M; Lou, Sijia; Liao, Hong; Guo, Jianping; Liu, Ying; Singh, Balwinder; Ghan, Steven J

    2017-05-11

    Eastern China has experienced severe and persistent winter haze episodes in recent years due to intensification of aerosol pollution. In addition to anthropogenic emissions, the winter aerosol pollution over eastern China is associated with unusual meteorological conditions, including weaker wind speeds. Here we show, based on model simulations, that during years with decreased wind speed, large decreases in dust emissions (29%) moderate the wintertime land-sea surface air temperature difference and further decrease winds by -0.06 (±0.05) m s -1 averaged over eastern China. The dust-induced lower winds enhance stagnation of air and account for about 13% of increasing aerosol concentrations over eastern China. Although recent increases in anthropogenic emissions are the main factor causing haze over eastern China, we conclude that natural emissions also exert a significant influence on the increases in wintertime aerosol concentrations, with important implications that need to be taken into account by air quality studies.

  5. Cultural Clues to the Middle Eastern Student. Occasional Paper No. 2.

    Science.gov (United States)

    Parker, Orin D.; And Others

    This paper discusses characteristics common to all Middle Eastern students with the exception of Israelis, and addresses itself to those working with Middle Eastern students on American college and university campuses. Middle Eastern students will show themselves to be highly adaptable, but they may demonstrate a formality of manner, particularly…

  6. Influences of eastern hemlock mortality on nutrient cycling

    Science.gov (United States)

    Thad E. Yorks; Jennifer C. Jenkins; Donald J. Leopold; Dudley J. Raynal; David A. Orwig

    2000-01-01

    Mortality of eastern hemlock (Tsuga canadensis (L.) Carriere) may be caused by a variety of agents, but hemlock trees of all sizes over a large geographic area are currently threatened by an outbreak of the hemlock woolly adelgid (HWA: Adelges tsugae Annand) in the eastern United States. In this paper, we review what is currently...

  7. Eastern Kentucky Teacher and Administrative Stress: Part II

    Science.gov (United States)

    Wright, Sam; Ballestero, Victor

    2012-01-01

    The purpose of this research was to survey selected Eastern Kentucky Teachers (Elementary, Middle, and High School) to collect data about stress in public schools. This was a continuation study for Eastern Kentucky that collected data on how men and women teachers and men and women administrators handle stress. A stress survey (Appendix C) was…

  8. Bulletin of Materials Science | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Wide-angle X-ray scattering (WAXS) recordings were carried out on raw Dharwar cotton fibres available in Karnataka. Using this data and employing linked atom least squares (LALS) method, we report here the molecular and crystal structure of these cotton fibres. Employing structural data, we have computed elastic ...

  9. 76 FR 25330 - Texas Eastern Transmission, LP; Notice of Request Under Blanket Authorization

    Science.gov (United States)

    2011-05-04

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP11-216-000] Texas Eastern... Eastern Transmission, LP (Texas Eastern), 5400 Westheimer Court, Houston, Texas 77056, filed in Docket No... in the termination of any services to Texas Eastern's customers, all as more fully set forth in the...

  10. EASTERN EUROPE, A REGION OF INSECURITY IN THE EUROPEAN UNION'S VICINITY

    Directory of Open Access Journals (Sweden)

    Bogdan – Lucian Cumpanasu

    2014-08-01

    Full Text Available During Cold War, the region of Eastern Europe was formed by European states that were behind the Iron Curtain.Once the communism has fallen and former Warsaw's Pact members have joined EU in 2004 and 2007 along with the Baltic republics, a New Eastern Europe comprising Ukraine, Republic of Moldova and the Caucasian Republics emerged at the border of EU. The north, west and south maritime frontiers of European Union are opposite with Eastern territorial one that are more difficult to control and defend against asymmetrical threats as: organized crime, drugs traffic, arms proliferation and illegal immigration. this paper aims to demonstrate that EU's policies initiated in the framework of Eastern Partnership (EaP that wanted to bring peace in the Eastern neighborhood did not succeed to fulfill the desired goals. One explanation is that EU did not take in consideration the Russian dream of redesigning its sphere of influence in Eastern Europe. Another one is that the cultural, political and social differences between EU and its EaP partners led to the failure of the project. Thus, European Union's actions toward Eastern vicinity led to a clash between two civilizations: East and West as well as to a geopolitical competition between Russian Federation and EU over their shared neighborhood.

  11. Comparison of Lamiaceae medicinal uses in eastern Morocco and eastern Andalusia and in Ibn al-Baytar's Compendium of Simple Medicaments (13th century CE).

    Science.gov (United States)

    El-Gharbaoui, Asmae; Benítez, Guillermo; González-Tejero, M Reyes; Molero-Mesa, Joaquín; Merzouki, Abderrahmane

    2017-04-18

    Transmission of traditional knowledge over time and across culturally and historically related territories is an important topic in ethnopharmacology. Here, we contribute to this knowledge by analysing data on medicinal uses in two neighbouring areas of the Western Mediterranean in relation to a historical text that has been scarcely mentioned in historical studies despite its interest. This paper discusses the sharing of popular knowledge on the medicinal uses of plants between eastern Morocco and eastern Andalusia (Spain), focusing on one of the most useful plant families in the Mediterranean area: Lamiaceae. Moreover, we used the classical work of Ibn al-Baytar (13th century CE) The Compendium of Simple Medicaments and Foods as a basis to contrast the possible link of this information, analysing the influence of this historical text on current popular tradition of medicinal plant use in both territories. For data collection, we performed ethnobotanical field research in the eastern part of Morocco, recording current medicinal uses for the Lamiaceae. In addition, we systematically reviewed the ethnobotanical literature from eastern Andalusia, developing a database. We investigated the possible historical link of the shared uses and included in this database the information from Ibn al-Baytar's Compendium. To compare the similarity and diversity of the data, we used Jaccard's similarity index. Our field work provided ethnobotanical information for 14 Lamiaceae species with 95 medicinal uses, serving to treat 13 different pathological groups. Of the total uses recorded in Morocco, 30.5% were shared by eastern Andalusia and found in Ibn al-Baytar's work. There was a higher similarity when comparing current uses of the geographically close territories of eastern Morocco and eastern Andalucía (64%) than for eastern Morocco and this historical text (43%). On the other hand, coincidences between current uses in eastern Andalusia and the ones related in the Compendium

  12. Polyphyly of the Padus group of Prunus (Rosaceae) and the evolution of biogeographic disjunctions between eastern Asia and eastern North America.

    Science.gov (United States)

    Liu, Xiao-Lin; Wen, Jun; Nie, Ze-Long; Johnson, Gabriel; Liang, Zong-Suo; Chang, Zhao-Yang

    2013-05-01

    Prunus subgenus Padus is a group with a wide distribution in temperate eastern Asia and eastern North America with one species extending to Europe and one to Central America. Phylogenetic relationships of subgenus Padus were reconstructed using sequences of nuclear ribosomal ITS, and plastid ndhF gene, and rps16 intron and rpl16 intron. Prunus subgenus Padus is shown to be polyphyletic. Taxa of subgenus Padus and subgenus Laurocerasus are highly intermixed in both the ITS and the plastid trees. The results support two disjunctions between eastern North America and Eurasia within the Padus group. One disjunction is between Prunus virginiana of eastern North America and P. padus of Eurasia, estimated to have diverged at 2.99 (95 % HPD 0.59-6.15)-4.1 (95 % HPD 0.63-8.59) mya. The other disjunction is between P. serotina and its Asian relatives. The second disjunction may have occurred earlier than the former one, but the age estimate is difficult due to the unresolved phylogenetic position of the P. serotina complex.

  13. Detrital zircons from samples of five Neo proterozoic sandstone units deposited on Uruguay and Argentina: about evolution of paleographic Rio de la Plata craton

    International Nuclear Information System (INIS)

    Gaucher, C.; Poire, D.G.; Pamoukaghlian, K.; Gomez Peral, L.; Finney, S.; Valencia, V.; Blanco, G.

    2007-01-01

    We report U-Pb ages of detrital zircons from samples of five Neoproterozoic sandstone units deposited on the Rio de la Plata Craton (RPC) in Uruguay and Argentina. Quartz-arenites of the Piedras de Afilar Formation show typical Transamazonian ages, with peaks at 2.00-2.07, 1.87 and 1.78 Ga. However, the most important zircon population is Mesoproterozoic, showing maxima at 1.49, 1.35, 1.25 and 1.0 Ga. Zircons recovered from two sandstone levels in the Arroyo del Soldado Group (Yerbal and Cerros San Francisco formations) are mostly Archean in age, with maxima at 3.2 and 2.7 Ga. Palaeoproterozoic zircons are also prominent in this unit, with peaks at 2.45 and 2.18, with the latter a typical Transamazonian age. Two samples from the Sierras Bayas Group in Tandilia (Argentina) show different age spectra. Sandstones of the Villa Monica Formation show a unimodal zircon population of Transamazonian age (peak at 2.13 Ga). Sandstones of the Cerro Largo Formation are characterized by a dominant Transamazonian zircon population (peaks at 2.15, 2.0 and 1.79), but also important Archean-lowermost Palaeoproterozoic (3.33, 2.99, 2.7, 2.47 Ga) and Mesoproterozoic peaks (1.55, 1.23 and 1.06). The abundance of Mesoproterozoic detrital zircons is surprising. A proto-Andean, Mesoproterozoic belt is suggested as the source of the Mesoproterozoic detritus. Archean rocks of the RPC crop out only in the Nico Perez Terrane in Uruguay, suggesting that the Nico Perez Terrane was much closer to Tandilia than it is today. The sinistral reactivation of the Sarandi del Yi Shear Zone in the Cambrian, as a result of tangential collision of the Cuchilla Dionisio-Pelotas Terrane, may explain this observations. The absence of Neoproterozoic zircons shows that the studied units were deposited in a stable continental margin opening to the East and South. These Neoproterozoic basins had obviously no contribution whatsoever from Brasiliano-Pan African belts, supporting the idea of Cambrian terrane

  14. Petrography and geochronology (U/Pb-Sm/Nd) the Passagem Granite, Pensamiento Granitoid Complex, Paragua Terrane, SW Amazon Craton, Mato Grosso, Brazil

    International Nuclear Information System (INIS)

    Jesus, Gisely Carmo de; Sousa, Maria Zelia Aguiar de; Ruiz, Amarildo Salina; Matos, Joao Batista de

    2010-01-01

    The Passagem granite includes stocks, plugs and dikes located in the Ricardo Franco hill - Vila Bela da Santissima Trindade region - state of Mato Grosso, central Brazil. The Passagem Granite is included in the Paragua terrane - SW Amazonian Craton. It consists of isotropic monzogranite, sienogranite and more rarely granodiorites with leucocratic dark gray to white color. These rocks range from hypidomorphic inequigranular to xenomorphic texture, fine to medium grained. Biotite is the only primary mafic present as essential phase and characterize an expanded slightly acid sequence formed by a sub-alkaline magmatism of high-potassium calc-alkaline, slightly peraluminous composition from arc magmatic tectonic environment during a post-collisional period. Mechanism of fractional crystallization of plagioclase, biotite, titanite, apatite and zircon associated with simultaneous crustal assimilation are suggested for the evolution of these rocks. The results support the hypothesis of a post-collisional magmatism in the Paragua terrane at 1284 +- 20 Ma corresponding to the crystallization age of the Passagem granite. This paper propose that Passagem Granite represents as an extension in Brazilian terrane of the Pensamiento Granitoid Complex. (author)

  15. 75 FR 22618 - Eastern Neck National Wildlife Refuge, Kent County, MD

    Science.gov (United States)

    2010-04-29

    ... DEPARTMENT OF THE INTERIOR Fish and Wildlife Service [FWS-R5-R-2009-N202; BAC-4311-K9-S3] Eastern... the environmental assessment (EA) for Eastern Neck National Wildlife Refuge (NWR). In this final CCP.... Agency Web Site: Download a copy of the document(s) at http://www.fws.gov/northeast/planning/Eastern...

  16. Western cratonic domains in Uruguay, geochronology

    International Nuclear Information System (INIS)

    Preciozzi, F; Pell, E; Muzio, R; Ledesma, J.J; Guerequiz, R

    2001-01-01

    The western cratonic domains in Uruguay are divided into three major units: Piedra Alta Terrane, Valentines Block and Pavas Terrane. Piedra Alta Terrane lacks of evidence of Neo proterozoic oro geneses (deformation, metamorphism or magmatism). Sarandi del Yi - Arroyo Solis Grande shear zone, separates it from Valentines Block. Valentines Block is separated from Pavas Terrane by Cueva del Tigre shear zone. Magmatic rocks with different ages, compositions and emplacements occur all over the Piedra Alta Terrane distributed in three metamorphic belts (Arroyo Grande, San Jose and Montevideo) as well as in the Central Gneissic-Migmatitic Complex. Samples from the gneissic-migmatitic complex, late tectonic granitoids and basic rocks associated to the metamorphic belts were analyzed using Rb/Sr, U/Pb, K/Ar and Sm/Nd methodologies. The age ranges obtained for granitoids and gneissicmigmatitic samples using Rb/Sr whole rock (WR) systematics are 1.7 to 2.5 Ga, showing two intervals: 1.9 to 2.05 Ga (intrusion of late granites) and 2.1 to 2.2 Ga (deformation and metamorphism). K/Ar cooling ages present several ranges: 1.3 to 1.35 Ga (probable local heating of the crust), 1.7 to 1.8 Ga (microgabbro magmatism, data confirmed by the Ar/Ar method) and ages between 2.0 to 2.2 Ga. Rb/Sr (WR) data yielded an isochronic age of 2094 ± 28.3 Ma, Ro = 0.70174 ± 0.00009, MSWD 19.74, interpreted as the time of the metamorphic event recognized for all the Piedra Alta Terrane. TDM Sm/Nd model ages presented a range from 2065 Ma to 2450 Ma. U/Pb systematics yield ages in migmatitic and gneissic rocks from 2.16 Ga to 2.21 Ga, showing metamorphism and deformation phenomena. While the ages of granitoids associated to the San Jose Belt are between 2.06 Ga and 2.08 Ga (Isla Mala) to 2.1 Ga (Granito de Cufre). None of them show metamorphic phenomena. Valentines Block (Preciozzi et al., 1979) comprises granulitic gneisses, granitoids and mafic rocks of different compositions. The geologic complexity

  17. Herbal mixtures in the traditional medicine of Eastern Cuba

    NARCIS (Netherlands)

    Hernández, J.; Volpato, G.

    2004-01-01

    Herbal mixtures in the traditional medicine of Eastern Cuba. Traditional herbal mixtures in Eastern Cuba are investigated through interviews with 130 knowledgeable people and traditional healers of the provinces of Santiago de Cuba and Guantanamo. One hundred seventy plant species and other products

  18. Pachybrachis (Coleoptera, Chrysomelidae, Cryptocephalinae) of Eastern Canada

    Science.gov (United States)

    Barney, Robert J.; LeSage, Laurent; Savard, Karine

    2013-01-01

    Abstract Seventeen Pachybrachis species occurring in eastern Canada [Ontario (ON), Québec (QC), New Brunswick (NB), Nova Scotia (NS), and Prince Edward Island (PE)] are treated by the authors. Two new national records were discovered, both from southernmost Ontario: P. cephalicus Fall and P. luctuosus Suffrian. Four species were new provincial records: P. cephalicus (ON), P. luctuosus (ON, QC), P. obsoletus Suffrian (NB), P. peccans (PE). A fully illustrated key to the Pachybrachis of eastern Canada is provided and supported with extensive photographs, distribution maps, and plant associations. Three species were distributed from southern Ontario into at least one province in the Maritimes (P. nigricornis (Say), P. obsoletus Suffrianand P. peccans Suffrian). Six species were distributed along the shores of the Great Lakes (Erie, Michigan, and Ontario) and rivers (Ottawa, Saguenay and St. Lawrence), but unknown from central and northern ON and QC (P. bivittatus (Say), P. hepaticus hepaticus (F. E. Melsheimer), P. othonus othonus (Say), P. pectoralis (F. E. Melsheimer), P. spumarius Suffrianand P. trinotatus (F. E. Melsheimer)). Seven species were rare, five being found exclusively from southern ON (P. calcaratus Fall, P. cephalicus, P. luridus (Fabricius), P. subfasciatus (J. E. LeConte)and P. tridens (F. E. Melsheimer)), with two having, in addition, a disjunct population in QC (P. atomarius (F. E. Melsheimer)and P. luctuosus). One species was found to be the northern most extension of an eastern United States (US) distribution into the eastern townships of QC (P. m-nigrum (F. E. Melsheimer)). There were no Pachybrachis that could be considered arctic, subarctic, or boreal species; no specimens were found from Labrador and Newfoundland, and all species had southern affinities. Pachybrachis atomarius, P. calcaratus, P. luridus, P. subfaciatus, and P. tridens, not seen over the last 30–70 years, may be extirpated from eastern Canada. PMID:24163583

  19. Faulting in eastern New Mexico: Revision 1

    International Nuclear Information System (INIS)

    Murphy, P.J.

    1987-08-01

    This area in eastern New Mexico is being studied because of its proximity to a proposed high-level nuclear waste repository site in Deaf Smith County, Texas. Regional and local tectonics must be thoroughly understood in order to be able to predict future tectonic activities in the site region. Hydrogeologic studies indicate that ground-water recharge, for regional deep and shallow aquifer systems, occurs primarily within the study area. Regional, easterly ground-water flow may be significantly affected by the spacing, orientation, and character of faults identified in this report. The tectonic history of eastern New Mexico is developed from information from 660 exploratory wells. A history of recurrent tectonic movements is evident, beginning possibly in the late Precambrian and extending into the late Cenozoic. The nature of the evidence includes the lateral and vertical distribution and the lithology of these deposits. The results are presented mainly as isopach and structure contour maps and as structural cross sections. The Paleozoic tectonic history of eastern New Mexico is similar and related to the history of the Texas Panhandle. Differences occur primarily in the Mesozoic and Cenozoic histories; tectonic uplift persisted for longer periods and faults show evidence of repeated movements in eastern New Mexico. This is probably a result of the proximity of the area to the Laramide and Basin and Range deformational events. 442 refs., 35 figs

  20. Eastern Arc Mountains and their national and global importance ...

    African Journals Online (AJOL)

    The Eastern Arc Mountains comprise a chain of separate mountain blocks running from southern Kenya through Tanzania in a crescent or arc shape. In Tanzania, the Eastern Arc consists of North and South Pare, East and West Usambaras, Nguru, Ukaguru, Rubeho, Uluguru, Udzungwa and Mahenge Mountains.

  1. 75 FR 68398 - Texas, Oklahoma & Eastern Railroad, LLC-Acquisition and Operation Exemption-Texas, Oklahoma...

    Science.gov (United States)

    2010-11-05

    ... & Eastern Railroad, LLC--Acquisition and Operation Exemption--Texas, Oklahoma & Eastern Railroad Company Texas, Oklahoma & Eastern Railroad, LLC (TOE), a noncarrier, has filed a verified notice of exemption under 49 CFR 1150.31 to acquire from Texas, Oklahoma & Eastern Railroad Company and to operate...

  2. Eastern Germany Ahead in Employment of Women

    OpenAIRE

    Elke Holst; Anna Wieber

    2014-01-01

    Almost a quarter of a century after the fall of the Wall, there are still more women in employment in eastern Germany than in the west. Although the disparity is marginal now, the two regions started from dramatically different levels. In 1991, immediately after reunification, the employment rate for women in western Germany was 54.6 percent, but since then it has increased year on year, reaching 67.5 percent in 2012. In eastern Germany, female employment initially plummeted after the fall of...

  3. 78 FR 66265 - Drawbridge Operation Regulation; Elizabeth River, Eastern Branch, Norfolk, VA

    Science.gov (United States)

    2013-11-05

    ... Operation Regulation; Elizabeth River, Eastern Branch, Norfolk, VA AGENCY: Coast Guard, DHS. ACTION: Notice... Elizabeth River Eastern Branch, mile 1.1, at Norfolk, VA. This deviation is necessary to facilitate... maintenance. The Norfolk Southern 5 railroad Bridge, at mile 1.1, across the Elizabeth River (Eastern Branch...

  4. Racial sexual mixing and factors associated with condom use among Middle Eastern-Canadians.

    Science.gov (United States)

    Schoueri, Nour; Bullock, Sandra L; Dubin, Joel A

    2010-02-01

    Interracial relationships in Canada have increased over the years. However, little research has focused on comparing STI/HIV risk and condom use between those in intra- and interracial relationships, specifically among Middle Eastern-Canadians. A web-based survey was administered to Middle Eastern-Canadians. Logistic regression analysis was used to assess factors associated with consistent condom use. Analyses were stratified by partner's race (Middle Eastern or non-Middle Eastern). The analysis sub-sample consisted of 92 participants. Factors associated with consistent condom use varied between the stratified groups. Among those with Middle Eastern partners, attitude towards marriage and the family and control in the relationship were associated with condom use. Among participants with non-Middle Eastern partners, acculturation and HIV knowledge were found to be associated with condom use. Factors associated with condom use varied between Middle Eastern-Canadians in intra- and interracial relationships. These differences illustrate the need for tailored interventions aimed at increasing condom use among this racial group.

  5. Quality of Antenatal care services in eastern Uganda: implications ...

    African Journals Online (AJOL)

    Good quality Antenatal Care (ANC) provides opportunity to detect and respond to risky maternal conditions. This study assessed quality of ANC services in eastern Uganda with a goal of benchmarking implications for interventions. Methods Data was collected from 15 health facilities in Eastern Uganda to establish capacity ...

  6. Eastern Canadian crude oil supply and its implications for regional energy security

    International Nuclear Information System (INIS)

    Hughes, Larry

    2010-01-01

    Canada has been blessed with immense energy resources; however, their distribution is not uniform. One such example is crude oil, which is found primarily in western Canada. Eastern Canada, consisting of the six eastern-most provinces (Newfoundland and Labrador, New Brunswick, Nova Scotia, Ontario, Prince Edward Island, and Quebec), produce limited quantities of crude oil, most of which is exported to the United States. Ideally, western Canadian crude oil would meet the demands of eastern Canada; however, the North American Free Trade Agreement (NAFTA) and the absence of oil pipelines means that eastern Canada increasingly relies on supplies of crude oil from a small number of oil exporting countries, many with declining production. This paper examines crude oil production, supply, and its refining in eastern Canada. It shows that crude production in the region has reached its peak and that increasing global competition for crude oil will affect energy security in eastern Canada, either through price increases or supply shortages, or both. (author)

  7. Seismic hazard in the eastern United States

    Science.gov (United States)

    Mueller, Charles; Boyd, Oliver; Petersen, Mark D.; Moschetti, Morgan P.; Rezaeian, Sanaz; Shumway, Allison

    2015-01-01

    The U.S. Geological Survey seismic hazard maps for the central and eastern United States were updated in 2014. We analyze results and changes for the eastern part of the region. Ratio maps are presented, along with tables of ground motions and deaggregations for selected cities. The Charleston fault model was revised, and a new fault source for Charlevoix was added. Background seismicity sources utilized an updated catalog, revised completeness and recurrence models, and a new adaptive smoothing procedure. Maximum-magnitude models and ground motion models were also updated. Broad, regional hazard reductions of 5%–20% are mostly attributed to new ground motion models with stronger near-source attenuation. The revised Charleston fault geometry redistributes local hazard, and the new Charlevoix source increases hazard in northern New England. Strong increases in mid- to high-frequency hazard at some locations—for example, southern New Hampshire, central Virginia, and eastern Tennessee—are attributed to updated catalogs and/or smoothing.

  8. REGIONALIZATION IN EASTERN AND CENTRAL EUROPE: OBSTACLES AND PERSPECTIVES

    Directory of Open Access Journals (Sweden)

    Gyula Horváth

    2012-01-01

    Full Text Available Regional policy depends on efficient administrative systems for designing and implementing strategies, and places considerable demands on Member States’ public administrations in terms of e.g. financial management and monitoring; project selection procedures; ex ante environmental impact assessments and cost-benefit analyses; and the monitoring and evaluation of outputs, results and impacts. EU member states have taken a range of different approaches to the administration of regional policy.The construction of regions in the countries of Eastern and Central Europe became one of the important debate topics for preparation for EU membership. Despite the numerous similarities in the changes that have taken place in the territorial structures of the Eastern and Central European countries, the differences in the responses individual countries gave to the challenges of regional development and the varied results of their development efforts demonstrate that the “Eastern European Bloc” is at least as heterogeneous as the former member states of the European Union. EU accession opened up a Pandora’s Box in the countries of Eastern and Central Europe. The fundamental issue of how unitarily structured states can be set on a decentralised path became the centre of debate. The paper introduces the Central and Eastern European achievements of region building processes and searches for an explanation of the reasons for the difficulties of Eastern and Central Europe in regional construction; it summarises the administrative and political development pre-requisites of the transition to a regional outline of the possible advantages of a regional institutional system in the creation of the Cohesion Policy ensuring a decrease in regional differences.

  9. Dementia in Eastern Mediterranean countries: A systematic review.

    Science.gov (United States)

    Yaghmour, Sara Mahmoud; Bartlett, Ruth; Brannelly, Tula

    2018-01-01

    Globally, there is an increase in the older population, whose lives are affected by local cultural norms. In Eastern Mediterranean countries, dementia is conventionally hidden from view with few dedicated services or recognition for diagnosis. The aim of this systematic review is to explore the limited literature on dementia and cognitive impairment among older people in Eastern Mediterranean countries to present an evaluation of current practices and to consolidate knowledge for future planning. Thirty-three studies were identified for inclusion in the review, and four themes were apparent. Firstly, prevalence, comorbidity and gender: In Eastern Mediterranean countries, many studies identify that the prevalence of dementia is high. As is the case elsewhere, many older adults in Eastern Mediterranean countries have at least one coexisting long-term condition, and some experience low life-satisfaction. Secondly, culture: In Eastern Mediterranean countries, the older adult is highly respected, and placement outside of the family home is considered an abandonment of family duty. The term dementia carries stigma, and it is widely believed that dementia is caused by 'fate'. Thirdly, recognition and tools: There is a lack of verified assessment instruments to assess for dementia. Despite concerns about the cultural appropriateness of the Mini-Mental State Exam, particularly for people who have low literacy levels, and low literacy being the norm in Eastern Mediterranean countries, the Mini-Mental State Examination is the main assessment instrument. Translation and transition of non-Arabic assessment instruments and tools with psychometric properties presents a challenge for clinicians. Finally, workforce issues: health care workers lack knowledge about dementia, as dementia care is a relatively recent addition to the nursing and medical syllabi. While there were some inconsistencies in the papers published, many of the articles call for increasing educational programmes

  10. Paleotsunamis in Eastern Taiwan

    Science.gov (United States)

    Yen, Jiun-Yee; Yu, Neng-Ti; Hirakawa, Kazuomi; Chyi, Shyh-Jeng; Huang, Shao-Yi

    2017-04-01

    Although Taiwan is located in the active collision zone between Eurasian and the Philippine Sea plate with very high seismicity in and surrounding the island, and supposedly highly susceptible to tsunami hazard. However, there is no record of tsunami hazard in the past one hundred years, and only very few historical records show some possible extreme event occurred. Therefore study of tsunami was scarce in Taiwan. Although historical records do show possible tsunami events, the records were too sparse and incomplete to confidently reconstruct the paleotsunami events. In the past few years, numerical simulations based on possible tsunami-genic zones near Taiwan show that the island could be affected by the correctly directed tsunami. Nevertheless, there is no detail, scientific research of paleotsunami records yet in Taiwan. Our field survey in eastern Taiwan (facing the western Pacific Ocean) along the coast uncovered several outcrops contain gravels embedded in well-developed soil layers. The rounded meta-sandstone gravels are clearly beach-origin and were brought to their current location upon extreme wave events, which is composed of either volcanic-clastic deposits from nearby hills or organic soil layers formed locally. Our investigation indicates that there are at least 3 events in the northern half of eastern Taiwan and at least 2 events in southern part of eastern Taiwan. Although these outcrops are next to the shoreline and Taiwan is susceptible from typhoons, these gravels could be farther away from the beach at the time of their deposition due to current high retreat rate of the sea cliff. Further investigations are needed to delineate possible sources of tsunamis that caused the deposits.

  11. Conservation assessments for five forest bat species in the Eastern United States

    Science.gov (United States)

    Frank R., III Thompson

    2006-01-01

    Assesses the status, distribution, conservation, and management considerations for five Regional Forester Sensitive Species of forest bats on national forests in the Eastern United States: eastern pipistrelle, evening bat, southeastern myotis, eastern small-footed myotis, and northern long-eared bat. Includes information on the taxonomy, description, life history,...

  12. 76 FR 61682 - Panhandle Eastern Pipe Line Company, LP; Notice of Application

    Science.gov (United States)

    2011-10-05

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. CP11-546-000] Panhandle Eastern Pipe Line Company, LP; Notice of Application On September 16, 2011, Panhandle Eastern Pipe Line... free). For TTY, call (202) 502-8659. Comment Date: 5 p.m. Eastern Time on October 19, 2011. Dated...

  13. Central and eastern European activities

    International Nuclear Information System (INIS)

    Rea, J.L.

    1993-01-01

    The Florida State University/Technical University of Budapest environmental research center, Center for Hungarian/American Environmental Research, Studies and Exchanges (CHAERSE), provides a resource base for information and technologies that is used to address near- and long-term environmental problems within the Department of Energy (DOE) complex and in Central and Eastern Europe. The CHAERSE is used as a technology transfer conduit for environmental restoration and waste management (ER/WM) problems and solutions. The International Technology Exchange Division (ITED) used the CHAERSE as one source of information for the identification of international ER/WM technologies being developed in Central and Eastern Europe. This was accomplished by matching high-priority problems in that region to high-priority problems in the DOE Complex; conducting symposia, meetings and workshops with international environmental experts; and identifying innovative technologies

  14. Rayleigh Wave Phase Velocities Beneath the Central and Southern East African Rift System

    Science.gov (United States)

    Adams, A. N.; Miller, J. C.

    2017-12-01

    This study uses the Automated Generalized Seismological Data Function (AGSDF) method to develop a model of Rayleigh wave phase velocities in the central and southern portions of the East African Rift System (EARS). These phase velocity models at periods of 20-100s lend insight into the lithospheric structures associated with surficial rifting and volcanism, as well as basement structures that pre-date and affect the course of rifting. A large dataset of >700 earthquakes is used, comprised of Mw=6.0+ events that occurred between the years 1995 and 2016. These events were recorded by a composite array of 176 stations from twelve non-contemporaneous seismic networks, each with a distinctive array geometry and station spacing. Several first-order features are resolved in this phase velocity model, confirming findings from previous studies. (1) Low velocities are observed in isolated regions along the Western Rift Branch and across the Eastern Rift Branch, corresponding to areas of active volcanism. (2) Two linear low velocity zones are imaged trending southeast and southwest from the Eastern Rift Branch in Tanzania, corresponding with areas of seismic activity and indicating possible incipient rifting. (3) High velocity regions are observed beneath both the Tanzania Craton and the Bangweulu Block. Furthermore, this model indicates several new findings. (1) High velocities beneath the Bangweulu Block extend to longer periods than those found beneath the Tanzania Craton, perhaps indicating that rifting processes have not altered the Bangweulu Block as extensively as the Tanzania Craton. (2) At long periods, the fast velocities beneath the Bangweulu Block extend eastwards beyond the surficial boundaries, to and possibly across the Malawi Rift. This may suggest the presence of older, thick blocks of lithosphere in regions where they are not exposed at the surface. (3) Finally, while the findings of this study correspond well with previous studies in regions of overlapping

  15. Mycoplasma gallopavonis in eastern wild turkeys.

    Science.gov (United States)

    Luttrell, M P; Eleazer, T H; Kleven, S H

    1992-04-01

    Serum samples and tracheal cultures were collected from eastern wild turkeys (Meleagris gallopavo sylvestris) trapped for relocation in South Carolina (USA) during 1985 to 1990. Sera were tested for Mycoplasma gallisepticum and M. synoviae by the rapid plate agglutination and hemagglutination inhibition tests and were found to be negative. Tracheal cultures were negative for all pathogenic Mycoplasma spp., including M. gallisepticum, M. synoviae, M. meleagridis, and M. iowae. However, M. gallopavonis was isolated from every group of wild turkeys tested in 1986 to 1990. These data suggest that M. gallopavonis, which is generally considered nonpathogenic, may be a common microorganism in eastern wild turkeys.

  16. Superposition de la tectonique éburnéenne et panafricaine dans les granitoïdes de la bordure nord du craton ouest africain, boutonniére de Zenaga, Anti-Atlas central, Maroc(Pan-african overprint on Eburnian granitoids at the northern boundary of the West African Craton, Zenaga Inlier, central Anti-Atlas, Morocco)

    Science.gov (United States)

    Ennih, N.; Laduron, D.; Greiling, R. O.; Errami, E.; de Wall, H.; Boutaleb, M.

    2001-05-01

    The Zenaga Inlier shows a comprehensive record of the Eburnian and Pan-African Orogenies. The Eburnian is characterised by high-temperature regional metamorphism and complex magmatism. The early (Azguemerzi) granodiorite has an isotopic mantle signature and was emplaced diapirically during the Eburnian Orogeny causing local thermal metamorphism. The foliation observed in this granitoid is a result of the interference between its primary syn-emplacement foliation and the regional foliation under amphibolite-facies conditions. The northern part of Zenaga has been intruded by the leucocratic granites of Tazenakht. These granites are cut by mylonites and phyllonites, corresponding to the Pan-African shear zones and accompanied with sub-greenschist-facies metamorphism during the Pan-African Orogeny. The deformation was the result of a regional sinistral transpressive event. This study in the northern part of the West African Craton shows the superposition of the Pan-African on the Eburnian Orogeny and the presence of a major fault in the Anti-Atlas.

  17. Large igneous provinces (LIPs) and carbonatites

    Science.gov (United States)

    Ernst, Richard E.; Bell, Keith

    2010-03-01

    There is increasing evidence that many carbonatites are linked both spatially and temporally with large igneous provinces (LIPs), i.e. high volume, short duration, intraplate-type, magmatic events consisting mainly of flood basalts and their plumbing systems (of dykes, sills and layered intrusions). Examples of LIP-carbonatite associations include: i. the 66 Ma Deccan flood basalt province associated with the Amba Dongar, Sarnu-Dandali (Barmer), and Mundwara carbonatites and associated alkali rocks, ii. the 130 Ma Paraná-Etendeka (e.g. Jacupiranga, Messum); iii. the 250 Ma Siberian LIP that includes a major alkaline province, Maimecha-Kotui with numerous carbonatites, iv. the ca. 370 Ma Kola Alkaline Province coeval with basaltic magmatism widespread in parts of the East European craton, and v. the 615-555 Ma CIMP (Central Iapetus Magmatic Province) of eastern Laurentia and western Baltica. In the Superior craton, Canada, a number of carbonatites are associated with the 1114-1085 Ma Keweenawan LIP and some are coeval with the pan-Superior 1880 Ma mafic-ultramafic magmatism. In addition, the Phalaborwa and Shiel carbonatites are associated with the 2055 Ma Bushveld event of the Kaapvaal craton. The frequency of this LIP-carbonatite association suggests that LIPs and carbonatites might be considered as different evolutionary ‘pathways’ in a single magmatic process/system. The isotopic mantle components FOZO, HIMU, EM1 but not DMM, along with primitive noble gas signatures in some carbonatites, suggest a sub-lithospheric mantle source for carbonatites, consistent with a plume/asthenospheric upwelling origin proposed for many LIPs.

  18. Left Dislocation in North-Eastern Neo-Aramaic dialects | Khan ...

    African Journals Online (AJOL)

    The North-Eastern Neo-Aramaic (NENA) dialects, which are the focus of this paper, were spoken across a wide area encompassing northern Iraq, north-west Iran, south-eastern Turkey, Armenia and Georgia. In these spoken dialects a distinction should be made between two major types of Left Dislocation (LD) structures.

  19. Uplift of quaternary shorelines in eastern Patagonia: Darwin revisited

    Science.gov (United States)

    Pedoja, Kevin; Regard, Vincent; Husson, Laurent; Martinod, Joseph; Guillaume, Benjamin; Fucks, Enrique; Iglesias, Maximiliano; Weill, Pierre

    2011-04-01

    During his journey on the Beagle, Darwin observed the uniformity in the elevation of coastal Eastern Patagonia along more than 2000 km. More than one century later, the sequences of Quaternary shorelines of eastern Patagonia have been described and their deposits dated but not yet interpreted in terms of geodynamics. Consequently, we i) mapped the repartition of the Quaternary coastal sequences in Argentinean Patagonia, ii) secured accurate altitudes of shoreline angles associated with erosional morphologies (i.e. marine terraces and notches), iii) took into account previous chrono-stratigraphical interpretations in order to calculate mean uplift rates since ~ 440 ka (MIS 11) and proposed age ranges for the higher and older features (up to ~ 180 m), and iv) focused on the Last Interglacial Maximum terrace (MIS 5e) as the best constrained marine terrace (in terms of age and altitude) in order to use it as a tectonic benchmark to quantify uplift rates along the entire passive margin of Eastern South America. Our results show that the eastern Patagonia uplift is constant through time and twice the uplift of the rest of the South American margin. We suggest that the enhanced uplift along the eastern Patagonian coast that interested Darwin during his journey around South America on the Beagle could originate from the subduction of the Chile ridge and the associated dynamic uplift.

  20. Effects of low-pressure igneous processes and subduction on Fe3+/ΣFe and redox state of mantle eclogites from Lace (Kaapvaal craton)

    Science.gov (United States)

    Aulbach, S.; Woodland, A. B.; Vasilyev, P.; Galvez, M. E.; Viljoen, K. S.

    2017-09-01

    Reconstructing the redox state of the mantle is critical in discussing the evolution of atmospheric composition through time. Kimberlite-borne mantle eclogite xenoliths, commonly interpreted as representing former oceanic crust, may record the chemical and physical state of Archaean and Proterozoic convecting mantle sources that generated their magmatic protoliths. However, their message is generally obscured by a range of primary (igneous differentiation) and secondary processes (seawater alteration, metamorphism, metasomatism). Here, we report the Fe3+/ΣFe ratio and δ18 O in garnet from in a suite of well-characterised mantle eclogite and pyroxenite xenoliths hosted in the Lace kimberlite (Kaapvaal craton), which originated as ca. 3 Ga-old ocean floor. Fe3+/ΣFe in garnet (0.01 to 0.063, median 0.02; n = 16) shows a negative correlation with jadeite content in clinopyroxene, suggesting increased partitioning of Fe3+ into clinopyroxene in the presence of monovalent cations with which it can form coupled substitutions. Jadeite-corrected Fe3+/ΣFe in garnet shows a broad negative trend with Eu*, consistent with incompatible behaviour of Fe3+ during olivine-plagioclase accumulation in the protoliths. This trend is partially obscured by increasing Fe3+ partitioning into garnet along a conductive cratonic geotherm. In contrast, NMORB-normalised Nd/Yb - a proxy of partial melt loss from subducting oceanic crust (1) - shows no obvious correlation with Fe3+/ΣFe, nor does garnet δ18OVSMOW (5.14 to 6.21‰) point to significant seawater alteration. Median bulk-rock Fe3+/ΣFe is roughly estimated at 0.025. This observation agrees with V/Sc systematics, which collectively point to a reduced Archaean convecting mantle source to the igneous protoliths of these eclogites compared to the modern MORB source. Oxygen fugacites (fO2) relative to the fayalite-magnetite-quartz buffer (FMQ) range from Δlog ⁡ fO2 = FMQ-1.3 to FMQ-4.6. At those reducing conditions, the solubility

  1. Census of biodiversity in marine caves of the eastern Mediterranean Sea

    Directory of Open Access Journals (Sweden)

    V. GEROVASILEIOU

    2015-03-01

    Full Text Available Scientific information on the biodiversity of marine caves in the eastern Mediterranean is limited, especially when considering the extensively studied caves of the north-western and central Mediterranean. Aiming to enhance current knowledge regarding cave communities, this study represents a first assessment of the marine cave biota of the eastern Mediterranean, as this has been defined by the European Union’s Marine Strategy Framework Directive (MSFD. Information retrieved from an extensive overview of relevant scientific documents was combined with original data recorded from 23 marine caves of the north-eastern Mediterranean. Our results report a total of 520 taxa recorded in eastern Mediterranean marine caves to date, the majority of which are sponges, polychaetes, rhodophytes, bivalves, fishes, and gastropods. These include several protected, endemic, and alien species. However, not all taxonomic groups have been equally studied among different areas and future studies are expected to raise the number of endemic and alien species. The overall observed trend is that the reported species number is generally related to sampling effort and scientific expertise. The most well-studied marine cave communities of the eastern Mediterranean are those of the Aegean Sea (especially its northern sector, which presented the highest number of species, followed by those of the Levantine. Furthermore, our research in Aegean caves revealed numerous new records for the marine cave fauna of the eastern basin, while several species are reported for the first time in the marine cave habitat. The critical need for further scientific research, monitoring, and conservation of this unique ecosystem was highlighted by (i the presence of certain species endemic to the eastern Mediterranean coupled with a high proportion of alien species, especially in the Levantine, and (ii the marine cave habitat availability in isolated insular areas of the eastern Mediterranean.

  2. Ozone and carbon monoxide budgets over the Eastern Mediterranean

    NARCIS (Netherlands)

    Myriokefalitakis, S.; Daskalakis, N.; Fanourgakis, G.S.; Voulgarakis, A.; Krol, M.C.; Brugh, Aan de J.M.J.; Kanakidou, M.

    2016-01-01

    The importance of the long-range transport (LRT) on O3 and CO budgets over the Eastern Mediterranean has been investigated using the state-of-the-art 3-dimensional global chemistry-transport model TM4-ECPL. A 3-D budget analysis has been performed separating the Eastern from the

  3. U-Pb age of the Anuri dyke: paleoproterozoic potassic alkaline magmatism and implications for the Transamazonic orogeny in the Sao Francisco Craton

    International Nuclear Information System (INIS)

    Conceicao, Herbet; Rios, Debora Correia; Oberli, Felix

    2007-01-01

    The Anuri Syenitic Dyke (72 km 2 ) is the south representative of a 1000 km N-S alignment of syenitic dykes which occur at the East Bahia. As the others bodies, Anuri is essentially composed of hypersolvus ultrapotassic syenites, which show the records of its differentiation by the presence of mafic-ultramafic apatite-rich cumulates. Its crystallization age of 2095- 4 Ma (U-Pb zircao ) is quite similar with results obtained for the other syenitic dykes, which suggest that their intrusions occur almost at the same time, sincronically, after the Transamazonic Orogeny climax. The geochemical data reveal that Anuri syenites are Ba, Sr, P, LREE enriched and show negative anomalies of Ti and Nb, suggesting a mantelic source subduction related. The initial Sr ratio and ε Nd values confirms the presence of this anomalous mantle. These data suggest that at the end of Transamazonic Orogeny, at the Sao Francisco Craton, there were particular conditions which allow the generation of alkaline magmas through the melting of an EMI reservoir. (author)

  4. 78 FR 9729 - Eastern States: Filing of Plat of Survey, North Carolina

    Science.gov (United States)

    2013-02-11

    ... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLES956000-L14200000-BJ0000] Eastern States..., on pages 318 through 319 a notice entitled ``Eastern States: Filing of Plats of Survey''. In said... Boundary, lands held in trust for the Eastern Band of Cherokee Indians, Swain County, in the State of North...

  5. THE CUBA COMPANY AND EASTERN CUBA’S ECONOMIC DEVELOPMENT, 1900-1959

    Directory of Open Access Journals (Sweden)

    Juan Carlos Santamarina

    2001-01-01

    Full Text Available This artide evaluates the Cuba Company’s impact on eastern Cuban economic development. It argues that the Cuba Company’s railroads, together with its development plans and strategies, helped stimulate the extraordinary economic growth of eastern Cuba between 1900 and 1959, especially in the production of sugar. Sugar was king in Cuba before 1900 but only inwestern Cuba; eastern Cuba produced only a minuscule fraction of total Cuban sugar production. Moreover, the Cuban Independence War of 1895-1898 had destroyed the industry. Due to the Cuba Company’s strategy, however, by the 1920s Cuba was once again the largest producer of sugar in the world and eastern Cuba represented over 50% of total Cuban sugarproduction.

  6. The prevalence of extreme Middle Eastern ideologies around the world.

    Science.gov (United States)

    Loza, Wagdy; Abd-el-Fatah, Youssef; Prinsloo, Johan; Hesselink-Louw, Anni; Seidler, Katie

    2011-02-01

    The Belief Diversity Scale (BDS) was administered to Australian, Canadian, Egyptian, and South African participants of different religious backgrounds. The BDS is a 33-item, six subscale instrument that is designed to quantitatively measure Middle Eastern extremist ideologies on risk areas that are reported in the literature. Results demonstrated the reliability and validity of the BDS, thus suggesting that the BDS could be used as an objective tool to measure Middle Eastern extremist ideologies. Results also supported the hypothesis of prevalence of Middle Eastern extremist ideologies around different parts of the world.

  7. CIS/Eastern countries. A curtain raising on eastern Europe

    International Nuclear Information System (INIS)

    Anon.

    1998-01-01

    Slowly and laboriously a new russian petroleum industry is setting in. To illustrate this new scenery, statistical data and maps, giving the production and consumption rates are presented. Two big companies (Shell and B.P.) stand for the privatization of Rosneft, the russian petroleum group. The legal and financial petroleum aspects of Russian are changing but very slowly, attracting the western companies around the petroleum industry. But this interest remains careful. The european bank of investment (BEI) decided to take a financial share in the eastern energy. (A.L.B.)

  8. «Eastern Partnership» after the Vilnius Summit

    Directory of Open Access Journals (Sweden)

    Anna Chernova

    2014-01-01

    Full Text Available The third summit of EU's Eastern Partnership held in Vilnius in November 2013 became a real turning point in the development of this organization. And it didn't happen due to signing of the first EU Association Agreement of its kind with the partner states but due to a sudden turn of the largest and most important of them - Ukraine - to the Russia's rival integration project. By doing so Ukraine at least temporarily joined two of the other participating countries: Armenia and Belarus, the latter of which is already in the Custom Union. At the other pole of the Eastern Partnership there are Georgia and Moldavia which initialed the Association and Free Trade agreements with the EU in Vilnius. This widening gap within the Eastern Partnership attracted everybody's attention to the EU - Russia rivalry in the post-Soviet countries which is increasingly interpreted in terms of the clash of civilizations. In this article we'd rather touch upon some of the peculiarities of the Eastern Partnership itself and its participating countries which to a large extent predetermined such an outcome. Among them is the ambiguous legacy of the European Neighbourhood Policy, lack of membership perspective in the EU as well as the nature of societies and elites in these post-Soviet states.

  9. Acaiaca Granulite Complex, MG: age, petrogenesis and tectonics implications

    International Nuclear Information System (INIS)

    Teixeira, W.; Kawashita, K.; Evangelista, H.J.; Taylor, P.N.

    1987-01-01

    Rb-SR and Pb-Pb geochronological work has been carried out on rocks from the Acaiaca granulite complex (mainly pyribolites, piriclasites and plagiogranulites) in Minas Gerais state. The results are interpreted together with petrographical and geochemical data, in order to delineate the evolution of those rocks. The Rb-Pb whole rock isochrons are concordant in age (around 2.0 b.y.) and they define the Transamazonian orogeny as the main event in the investigated area. In addition, the Sr and Pb evidences suggest a strong reworking of prior continental crust at that time. In turn, the estimation of P-T conditions of regional metamorphism based on geo thermo barometric calculations and on petrology resulted in T ≅ 700-900 O C and P tot =5,6-8 and 8-10 Kbar. The whole group of data is coherent with the development of is Transamazonian mobile zone of ensialic character, along the eastern border of an Archaean fragment. Within an area considered cratonic during the Upper Proterozoic. A model of evolution of the Sao Francisco Craton as well the differences between the Archaean and early Proterozoic domains are discussed. (M.V.M.)

  10. The Punta del Este Suspect Terrane: a possible counterpart in Eastern Uruguay of the Namaqua Complex and Gariep Belt in Western Africa

    International Nuclear Information System (INIS)

    Preciozzi, F.; Basei, M.; Peel, E.

    2005-01-01

    two tectono-stratigraphic sets with the eastern portion occupied by parautochthonous units of a passive continental margin (Port Nolloth Zone) and a western allochthonous domain (Marmora Terrane). The evidences of blueschist facies metamorphism, countless times referred in the literature (Kröner, 1974; Porada, 1979), have been recently ruled out by Frimmel and Hartnady (1992). The sedimentation period of the Gariep Group is attributed to the Neoproterozoic because it lays discordantly on the rhyolite units (Ross Pinah Formation) dated by the single zircon evaporation technique as 735Ma (Frimmel, 1995). Meert §& Van der Voo (1994) correlated diamictite intercalations, probably of age between 580 and 560 Ma, in the upper portion of the Gariep Group with the glacial deposits of Vendian age. The northeastern portion of the Gariep Group is covered by not metamorphosed sediments of the Nama Group. In the South-American counterpart, that is, the South-Brazilian region and the Uruguayan territory, an old western domain is observed The Central Domain is represented by the Rio de La Plata Craton (sensus Almeida et al.,1973) ,by de Nico Perez Terrane (Bossi et al.,1992 ;Valentines Block,PavasTerrane (Preciozzi et al.,1979) and the Rivera granitic-gneissic complex ..All of them were generated or intensively reworked during the Neoproterozoic, distributed along its eastern border and as a whole organised in the NE-SW direction. In these domain, a granitic-migmatitic infrastructure and sedimentary basins and low- to medium metamorphic grade covers predominate, related to the Lavalleja-supergroup and Zanja del Cerro Grande Group The Rocha formation is developed as a metasedimentary cover in the Punta del Este Terrane,being associated to the Atlantic Domain. Geochronologic studies recently performed in the southeastern portion of Uruguay allowed the identification of igneous rocks with U-Pb ages in zircons ranging from 650 to 1000Ma. These ages, added to the geological

  11. Geochemistry and Nd-Sr isotopic signatures of the Pensamiento Granitoid Complex, Rondonian-San Ignacio Province, eastern precambrian shield of Bolivia: petrogenetic constraints for a mesoproterozoic magmatic arc setting

    International Nuclear Information System (INIS)

    Matos, Ramiro; Teixeira, Wilson; Bettencourt, Jorge Silva; Geraldes, Mauro Cesar

    2009-01-01

    The Pensamiento Granitoid Complex (PGC), located in the northern part of the eastern Precambrian shield of Bolivia, is tectonically assigned to the Rondonian-San Ignacio Province (1.55 - 1.30 Ga) of the Amazonian Craton that is made up by Archean and Proterozoic provinces. The Proterozoic ones result from accretionary orogens that become successively younger south westwards, such as the Rondonian/San Ignacio (1.37 - 1.32 Ga) and the Sunsas orogenies (1.20 - 1.00 Ga). The PGC crops out mainly on the 'Paragua craton' bounded to the south by the Sunsas belt, and composed of granites and subvolcanic terms, and subordinately of syenites, granodiorites, tonalites, trondhjemites and diorites as orogenic representatives of the Rondonian/San Ignacio Orogeny, intrusive into the Lomas Maneches (ca. 1.68 Ga) and Chiquitania (ca. 1.7 Ga) complexes. Thirteen whole rock chemical analyses for major, trace and REE elements were performed for the La Junta, San Martin, Diamantina, Porvernir, San Cristobal, Piso Firme plutons of the PGC. The negative trends of MgO, Al 2 O 3 and CaO contents with increasing SiO 2 suggest that fractional crystallization played an important role in the petrogenesis of the investigated rocks. The data also indicate a mainly peraluminous, sub-alkaline to high-K calc-alkaline composition, and fractionated LREE/HREE patterns are consistent with a magmatic arc character for these plutons. SHRIMP U-Pb zircon ages of the La Junta and San Martin syn- to late-kinematic plutons are 1347 ± 21 Ma and 1373 ± 20 Ma respectively, and the Sm-Nd T DM model ages are between 1.9 to 2.0 Ga, while ε Nd(1330) values range from +1.8 to -4.3, respectively. In addition, the late- to post-kinematic Diamantina pluton yields SHRIMP U-Pb zircon age of 1340 ± 20 Ma, and variable Sm-Nd T DM model ages (1.6 to 1.9 Ga) and ε Nd(1330) values (+0.4 to -1.2) that are comparable with previous results found for other coeval plutons. The Porvenir, San Cristobal and Piso Firme plutons

  12. Petrogenesis of shoshonitic granitoids, eastern India: Implications for the late Grenvillian post-collisional magmatism

    Directory of Open Access Journals (Sweden)

    B. Goswami

    2014-11-01

    Full Text Available Many elongated, lenticular plutons of porphyritic granitoids are distributed mainly near the southern and northern margin of the Chhotanagpur Gneissic Complex (CGC which belongs to the EW to ENE–WSW tending 1500 km long Proterozoic orogenic belt amalgamating the North and South Indian cratonic blocks. The late Grenvillian (1071 ± 64 Ma Raghunathpur porphyritic granitoid gneiss (PGG batholith comprising alkali feldspar granite, granite, granodiorite, tonalite, quartz syenite and quartz monzonite intruded into the granitoid gneisses of southeastern part of CGC in the Purulia district, West Bengal and is aligned with ENE–WSW trending North Purulia shear zone. Mineral chemistry, geochemistry, physical condition of crystallization and petrogenetic model of Raghunathpur PGG have been discussed for the first time. The petrographic and geochemical features (including major and trace-elements, mineral chemistry and 87Sr/86Sr ratio suggest these granitoids to be classified as the shoshonitic type. Raghunathpur batholith was emplaced at around 800 °C and at 6 kbar pressure tectonic discrimination diagrams reveal a post-collision tectonic setting while structural studies reveal its emplacement in the extensional fissure of North Purulia shear zone. The Raghunathpur granitoid is compared with some similar granitoids of Europe and China to draw its petrogenetic model. Hybridization of mantle-generated enriched mafic magma and crustal magma at lower crust and later fractional crystallization is proposed for the petrogenesis of this PGG. Mafic magma generated in a post-collisional extension possibly because of delamination of subducting slab. Raghunathpur batholith had emplaced in the CGC during the final amalgamation (∼1.0 Ga of the North and South Indian cratonic blocks. Granitoid magma, after its generation at depth, was transported to its present level along megadyke channel, ways within shear zones.

  13. Contemporaneous assembly of Western Gondwana and final Rodinia break-up: Implications for the supercontinent cycle

    Directory of Open Access Journals (Sweden)

    Sebastián Oriolo

    2017-11-01

    Full Text Available Geological, geochronological and isotopic data are integrated in order to present a revised model for the Neoproterozoic evolution of Western Gondwana. Although the classical geodynamic scenario assumed for the period 800–700 Ma is related to Rodinia break-up and the consequent opening of major oceanic basins, a significantly different tectonic evolution can be inferred for most Western Gondwana cratons. These cratons occupied a marginal position in the southern hemisphere with respect to Rodinia and recorded subduction with back-arc extension, island arc development and limited formation of oceanic crust in internal oceans. This period was thus characterized by increased crustal growth in Western Gondwana, resulting from addition of juvenile continental crust along convergent margins. In contrast, crustal reworking and metacratonization were dominant during the subsequent assembly of Gondwana. The Río de la Plata, Congo-São Francisco, West African and Amazonian cratons collided at ca. 630–600 Ma along the West Gondwana Orogen. These events overlap in time with the onset of the opening of the Iapetus Ocean at ca. 610–600 Ma, which gave rise to the separation of Baltica, Laurentia and Amazonia and resulted from the final Rodinia break-up. The East African/Antarctic Orogen recorded the subsequent amalgamation of Western and Eastern Gondwana after ca. 580 Ma, contemporaneously with the beginning of subduction in the Terra Australis Orogen along the southern Gondwana margin. However, the Kalahari Craton was lately incorporated during the Late Ediacaran–Early Cambrian. The proposed Gondwana evolution rules out the existence of Pannotia, as the final Gondwana amalgamation postdates latest connections between Laurentia and Amazonia. Additionally, a combination of introversion and extroversion is proposed for the assembly of Gondwana. The contemporaneous record of final Rodinia break-up and Gondwana assembly has major implications for the

  14. Satellite gravity gradient views help reveal the Antarctic lithosphere

    Science.gov (United States)

    Ferraccioli, F.; Ebbing, J.; Pappa, F.; Kern, M.; Forsberg, R.

    2017-12-01

    Here we present and analyse satellite gravity gradient signatures derived from GOCE and superimpose these on tectonic and bedrock topography elements, as well as seismically-derived estimates of crustal thickness for the Antarctic continent. The GIU satellite gravity component images the contrast between the thinner crust and lithosphere underlying the West Antarctic Rift System and the Weddell Sea Rift System and the thicker lithosphere of East Antarctica. The new images also suggest that more distributed wide-mode lithospheric and crustal extension affects both the Ross Sea Embayment and the less well known Ross Ice Shelf segment of the rift system. However, this pattern is less clear towards the Bellingshousen Embayment, indicating that the rift system narrows towards the southern edge of the Antarctic Peninsula. In East Antarctica, the satellite gravity data provides new views into the Archean to Mesoproterozoic Terre Adelie Craton, and clearly shows the contrast wrt to the crust and lithosphere underlying both the Wilkes Subglacial Basin to the east and the Sabrina Subglacial Basin to the west. This finding augments recent interpretations of aeromagnetic and airborne gravity data over the region, suggesting that the Mawson Continent is a composite lithospheric-scale entity, which was affected by several Paleoproterozoic and Mesoproterozoic orogenic events. Thick crust is imaged beneath the Transantarctic Mountains, the Terre Adelie Craton, the Gamburtsev Subglacial Mountains and also Eastern Dronning Maud Land, in particular beneath the recently proposed region of the Tonian Oceanic Arc Superterrane. The GIA and GIU components help delineate the edges of several of these lithospheric provinces. One of the most prominent lithospheric-scale features discovered in East Antarctica from satellite gravity gradient imaging is the Trans East Antarctic Shear Zone that separates the Gamburtsev Province from the Eastern Dronning Maud Land Province and appears to form the

  15. High-grade iron ore at Windarling, Yilgarn Craton: a product of syn-orogenic deformation, hypogene hydrothermal alteration and supergene modification in an Archean BIF-basalt lithostratigraphy

    Science.gov (United States)

    Angerer, Thomas; Hagemann, Steffen G.; Danyushevsky, Leonid

    2013-08-01

    Banded iron formation (BIF)-hosted iron ore deposits in the Windarling Range are located in the lower greenstone succession of the Marda-Diemals greenstone belt, Southern Cross domain, Yilgarn Craton and constitute a total hematite-martite-goethite ore resource of minimum 52 Mt at 60 wt.% Fe (0.07 P). Banded iron formation is interlayered with high-Mg basalts at Windarling and precipitated during episodes of volcanic quiescence. Trace element content and the rare earth element (REE) ratios Y/Ho (42 to 45), Sm/Yb (1.5), together with positive La and Gd anomalies in `least-altered' hematite-magnetite-metachert-BIF indicate the precipitation from Archean seawater that was fertilised by hydrothermal vent fluids with a basaltic HREE-Y signature. Hypogene iron ore in sub-greenschist facies metamorphosed BIF formed during three distinct stages: ore stage 1 was a syn- to post-metamorphic, syn-D1, Fe-Ca-Mg-Ni-Co-P-REE metasomatism that produced local Ni-REE-rich Fe-dolomite-magnetite alteration in BIF. Hydrothermal alteration was induced by hot fluid flow controlled by brittle-ductile reactivation of BIF-basalt margins and crosscutting D1 faults. The Ni-Co-rich content of dolomite and a shift in REE ratios in carbonate-altered BIF towards Archean mafic rock signature (Y/Ho to 31 to 40, Sm/Yb to 1 to 2 and Gd/Gd* to 1.2 to 1.4) suggest that high-Mg basalts in the Windarling Range were the primary source of introduced metals. During ore stage 2, a syn-deformational and likely acidic and oxidised fluid flow along BIF-basalt margins and within D1 faults leached carbonate and precipitated lepidoblastic and anhedral/granoblastic hematite. High-grade magnetite-hematite ore is formed during this stage. Ore stage 3 hydrothermal specular hematite (spcH)-Fe-dolomite-quartz alteration was controlled by a late-orogenic, brittle, compressional/transpressional stage (D4; the regional-scale shear-zone-related D3 is not preserved in Windarling). This minor event remobilised iron oxides

  16. Economic restructuring in Eastern Europe and acid rain abatement strategies

    International Nuclear Information System (INIS)

    Amann, Markus; Klaassen, Ger; Schoepp, Wolfgang; Soerensen, Lene; Hordijk, Leen

    1992-01-01

    Acid rain abatement strategies in Europe are currently being discussed in view of the expiration of the Helsinki Protocol on SO 2 emission reduction. The changing energy situation in Eastern European countries is expected to have an influence on the deposition pattern in Europe. The paper presents a consistent energy scenario for Eastern European countries and compares optimal strategies to reduce SO 2 emissions. These strategies are based on runs with the RAINS model in which environmental targets have been set based on critical loads for sulphur. The analysis shows that economic restructuring and efficiency improvements in Eastern European countries, as well as in Western Europe, may result in significantly lower sulphur abatement costs. Potential assistance to Eastern Europe to guarantee desired environmental standards in Western countries should therefore focus not only on providing emission control devices but also on the success of the economic transition process. (author)

  17. Energy in Eastern Europe

    International Nuclear Information System (INIS)

    Bouma, J.W.J.

    1993-01-01

    The present energy market in Central and Eastern Europe differs strongly from the energy situation in open market economies. Compared to the European Communities, the energy market in Central and eastern Europe is characterized by its high energy intensity, high quantity of imported oil and gas from a one country (the ex-Soviet Union), the dominant role of solid fossil fuels in some countries, and environmental pollution. Expected future developments are the reduction of the energy intensity and the total energy consumption, the reduction of the industrial energy consumption, the reduction of the solid fossil fuels as well as the geographic distribution of energy import. The restructuring of the energy industry has been started by introducing a market orientated policy including privatisation and the promotion of the free play of price-making forces, accompanied by relatively small-scale investments. Recent data indicate a decrease of energy consumption due to the economic decline and the shut-down of companies in the heavy industries. (A.S.) 4 figs. 5 tabs

  18. Pipelines to eastern Canada

    International Nuclear Information System (INIS)

    Otsason, J.

    1998-01-01

    This presentation focused on four main topics: (1) the existing path of pipelines to eastern Canada, (2) the Chicago hub, (3) transport alternatives, and (4) the Vector Pipeline' expansion plans. In the eastern Canadian market, TransCanada Pipelines dominates 96 per cent of the market share and is effectively immune to expansion costs. Issues regarding the attractiveness of the Chicago hub were addressed. One attractive feature is that the Chicago hub has access to multiple supply basins including western Canada, the Gulf Coast, the mid-continent, and the Rockies. Regarding Vector Pipelines' future plans, the company proposes to construct 343 miles of pipeline from Joliet, Illinois to Dawn, Ontario. Project description included discussion of some of the perceived advantages of this route, namely, extensive storage in Michigan and south-western Ontario, the fact that the proposed pipeline traverses major markets which would mitigate excess capacity concerns, arbitrage opportunities, cost effective expansion capability reducing tolls, and likely lower landed costs in Ontario. Project schedule, costs, rates and tariffs are also discussed. tabs., figs

  19. A study of melanoma in Eastern European migrants in Italy.

    Science.gov (United States)

    Astrua, Chiara; Fava, Paolo; Brizio, Matteo; Savoia, Paola

    2017-04-01

    Cancer survival rates are lower in Eastern Europe. To describe, based on a single-centre database in northern Italy, clinical, histopathological, and prognostic features of melanoma in a migrant population from Eastern Europe. We retrospectively analysed data from 18,190 consecutive foreign patients who visited our institution, with 49 cases of melanoma from Eastern Europe. The control group was represented by 1,003 Italian melanoma patients diagnosed and followed at our centre during the same time period. Patients from Eastern Europe were mainly females with lower median age, without significant differences regarding primary melanoma site, relative to the control group. Diagnosis was made at the place of birth in 30.6% and in our centre for the remainder. Median Breslow thickness was greater (p = 0.0178), and aggressive histotypes (p = 0.0017) and ulcerated melanomas (p = 0.002) were significantly over-represented, particularly when diagnosed in the patients' native country. Disease was more advanced at diagnosis (p = 0.0001), regardless of the place of initial diagnosis (51% had a progressive disease within one year which rose to 80% if diagnosed before admission to our centre), and the percentage of patients who died within one year was significantly higher (p = 0.022), relative to the control group. Our study shows a poor prognosis for melanoma patients diagnosed in Eastern Europe. Moreover, for migrant populations moving from Eastern to Western European countries, financial difficulties, poor social integration, and language barriers, with consequent late access to healthcare facilities, may account for a worse prognosis.

  20. Currency substitution in Eastern Europe

    NARCIS (Netherlands)

    van Aarle, B.; Budina, N.

    1995-01-01

    Monetary instability during the transition process from a command economy to a market economy has induced a considerable increase in currency substitution in Eastern Europe. Currency substitution itself affects monetary stability since it reduces the stability of velocity. This paper investigates