WorldWideScience

Sample records for mafic microgranular enclaves

  1. An isotopic study of mafic microgranular enclaves in the Katsuragi adakitic tonalite, southwestern Japan.

    Science.gov (United States)

    Tezuka, N.; Tsuboi, M.; Asahara, Y.

    2017-12-01

    The Cretaceous Katsuragi tonalite in southwestern Japan has been regarded as adakite formed by the partial melting of lower crust a) b). The tonalite is 10 x 15 km in areal extent, is composed of hornblende-biotite tonalite with a mineral assemblage of plagioclase, biotite, quartz and hornblende, and contains mafic microgranular enclaves (MME). The MME has dioritic composition with a mineral assemblage of plagioclase, biotite, hornblende and quartz. The boundary between the tonalite and the MME is sharp. To reveal the relationship between the MME and adakitic feature of the host tonalite, we have focused on the chemical and Sr-Nd isotopic compositions of the MME in the Katsuragi tonalite. Three models have been proposed for the origin of MME: restite, magma-mixing, and cumulate c). In the restite model, MME is regarded as a residual material of partial melting, and therefore chemical compositions of MME and host should show a linear trend on the Harker's diagram. However, the Katsuragi tonalite and its MME do not show one linear trend. Based on mixing of two magmas, initial 87Sr/86Sr (SrI) value of MME is basically different from that of its host. However, the SrI value of the MME is 0.70725-0.70749 and is identical to the value of 0.70728 in the Katsuragi tonalite d), indicating one magma source for the MME and its host. According to the cumulate model, MME forms from cumulate piles by subsequent feeding of congenetic magma immediately after the early crystallized minerals are solidified. The concordance of the age and SrI between the Katsuragi tonalite and its MME strongly indicate the cumulate origin c). Furthermore, the mineral assemblage of the MME resembles with the common mineral assemblage of andesitic cumulate such as plagioclase, hornblende and quartz c), and this is consistent with the cumulate model. Based on the cumulate origin of the MME, the adakitic feature of chemical composition in the host rock is potentially formed by the separation of cumulate

  2. Mafic microgranular enclave swarms in the Chenar granitoid stock, NW of Kerman, Iran: evidence for magma mingling

    Science.gov (United States)

    Arvin, M.; Dargahi, S.; Babaei, A. A.

    2004-10-01

    Mafic microgranular enclaves (MME) are common in the Early to Middle Miocene Chenar granitoid stock, northwest of Kerman, which is a part of Central Iranian Eocene volcanic belt. They occur individually and in homogeneous or heterogeneous swarms. The MME form a number of two-dimensional structural arrangements, such as dykes, small rafts, vortices, folded lens-shapes and late swarms. The enclaves are elongated, rounded to non-elongated and subrounded in shape and often show some size-sorting parallel to direction of flow. Variation in the elongation of enclaves could reflect variations in the viscosity of the enclave, the time available for enclave deformation and differential strain during flow of the host granitoid magma. The most effective mechanism in the formation of enclave swarms in the Chenar granitoid stock was velocity gradient-related convection currents in the granitoid magma chamber. Gravitational sorting and the break-up of heterogeneous dykes also form MME swarms. The MME (mainly diorite to diorite gabbro) have igneous mineralogy and texture, and are marked by sharp contacts next to their host granitoid rocks. The contact is often marked by a chilled margin with no sign of solid state deformation. Evidence of disequilibrium is manifested in feldspars by oscillatory zoning, resorbed rims, mantling and punctuated growth, together with overgrowth of clinopyroxene/amphibole on quartz crystals, the acicular habit of apatites and the development of Fe-Ti oxides along clinopyroxene cleavages. These observations suggest that the MMEs are derived from a hybrid-magma formed as a result of the intrusion of a mafic magma into the base of a felsic magma chamber. The density contrast between hybrid-magma and the overlying felsic magma was reduced by the release of dissolved fluids and the ascent of exsolved gas bubbles from the mafic magma into the hybrid zone. Further convection in the magma chamber dispersed the hybridized magma as globules in the upper parts of

  3. Origin of the mafic microgranular enclaves (MMEs) and their host granitoids from the Tagong pluton in Songpan-Ganze terrane: An igneous response to the closure of the Paleo-Tethys ocean

    Science.gov (United States)

    Chen, Qiong; Sun, Min; Zhao, Guochun; Yang, Fengli; Long, Xiaoping; Li, Jianhua; Wang, Jun; Yu, Yang

    2017-10-01

    The Songpan-Ganze terrane is mainly composed of a Triassic sedimentary sequence and late Triassic-Jurassic igneous rocks. A large number of plutons were emplaced as a result of tectono-magmatic activity related to the late stages of Paleo-Tethys ocean closure and ensuing collision. Granitoids and their hosted mafic enclaves can provide important constraints on the crust-mantle interaction and continental crustal growth. Mesozoic magmatism of Songpan-Ganze remains enigmatic with regard to their magma generation and geodynamic evolution. The Tagong pluton (209 Ma), in the eastern part of the Songpan-Ganze terrane, consists mainly of monzogranite and granodiorite with abundant coeval mafic microgranular enclaves (MMEs) (ca. 208-209 Ma). The pluton comprises I-type granitoid that possesses intermediate to acidic compositions (SiO2 = 61.6-65.8 wt.%), high potassium (K2O = 3.2-4.1 wt.%), and high Mg# (51-54). They are also characterized by arc-type enrichment of LREEs and LILEs, depletion of HFSEs (e.g. Nb, Ta, Ti) and moderate Eu depletions (Eu/Eu* = 0.46-0.63). Their evolved zircon Hf and whole-rock Nd isotopic compositions indicate that their precursor magmas were likely generated by melting of old lower continental crust. Comparatively, the MMEs have lower SiO2 (53.4-58.2 wt.%), higher Mg# (54-67) and show covariation of major and trace elements, coupled with field and petrographic observations, such as the disequilibrium textures of plagioclase and amphibole, indicating that the MMEs and host granitoids were originated from different magma sources but underwent mafic-felsic magma mixing process. Geochemical and isotopic data further suggest that the precursor magma of the MMEs was formed in the continental arc setting, mainly derived from an ancient metasomatized lithospheric mantle wedge. The Triassic granitoids from the Songpan-Ganze terrane show remarkable temporal-spatial-petrogenetic affinities to the counterparts of subduction zones in the Yidun and Kunlun arc

  4. Origins of igneous microgranular enclaves in granites: the example of Central Victoria, Australia

    Science.gov (United States)

    Clemens, J. D.; Elburg, M. A.; Harris, C.

    2017-10-01

    To investigate their genesis and relations with their host rocks, we study igneous microgranular enclaves (IMEs) in the c. 370 Ma, post-orogenic, high-level, felsic plutons and volcanic rocks of Central Victoria, Australia. The IMEs are thermally quenched magma globules but are not autoliths, and they do not form mixing series with their host magmas. These IMEs generally represent hybrids between mantle-derived magmas and very high- T crust-derived melts, modified by fractionation, ingestion of host-derived crystals and, to a lesser extent, by chemical interactions with their hosts. Isotopic and elemental evidence suggests that their likely mafic progenitors formed by partial melting of subcontinental mantle, but that the IME suites from different felsic host bodies did not share a common initial composition. We infer that melts of heterogeneous mantle underwent high- T hybridisation with melts from a variety of crustal rocks, which led to a high degree of primary variability in the IME magmas. Our model for the formation of the Central Victorian IMEs is likely to be applicable to other occurrences, especially in suites of postorogenic granitic magmas emplaced in the shallow crust. However, there are many different origins for the mingled magma globules that we call IMEs, and different phenomena seem to occur in differing tectonic settings. The complexity of IME formation means that it is difficult to unravel the petrogenesis of these products of chaotic magma processes. Nevertheless, the survival of fine-grained, non-equilibrium mineralogy and texture in the IMEs suggests that their tenure in the host magmas must have been geologically brief.

  5. Mafic enclaves in dacitic domes and their relation with La Poruña scoria cone, Central Andes, northern Chile

    Science.gov (United States)

    González-Maurel, O. P.; Gallmeyer, G.; Godoy, B.; Menzies, A.; le Roux, P. J.; Harris, C.

    2017-12-01

    Chao Dacite, Chillahuita, Cerro Pabellón, Chanka, Chac-Inca, and Cerro La Torta (or Tocorpuri) are dacitic domes of late Pleistocene age (30 to 140 ka; Renzulli et al., 2006; Tierney et al., 2016) located in Northern Chilean Central Andean province (NCCA; 17°20'S - 27°40'S). While, La Poruña is a 180 m high basaltic-andesite scoria cone erupted ca. 100 ka (Wörner et al., 2000). This scoria cone is also located at the NCCA, 26 km to the SW of Chanka and 45 km to the NW of Chao Dacite. The dacitic domes are generally porphyritic and highly crystalline lavas (30 - 50 vol % phenocrysts, plagioclase > biotite > amphibole > quartz ≥ accessory), with hyalopilitic or intersertal groundmass. These domes contain mafic enclaves, mostly andesite in composition, with plagioclase > amphibole > biotite ≥ clinopyroxene ≥ olivine ≥ accessory phenocryst (10 - 20 vol %) in a lightly oxidized groundmass with intersertal or intergranular textures. In contrast, La Poruña rocks are mostly aphanitic (75 - 85 vol % groundmass) and highly vesicular, with plagioclase > olivine ≥ clinopyroxene ≥ orthopyroxene phenocrysts in an intersertal or hyalopilitic groundmass. Although petrographically different, the composition (57 wt % SiO2; 580 ppm Sr, 87Sr/86Sr = 0.7066) of mafic enclaves from Cerro Pabellón dome are similar to the lava flows and pyroclastic blocks of La Poruña scoria cone (55 - 59 wt % SiO2; 560 - 610 ppm Sr; 0.7062 - 0.7066 87Sr/86Sr). Based on this data and the eruption ages of these volcanic structures, we suggest that the mafic enclaves and La Poruña magmas are co-genetic. Thus, we propose that the genesis of these mafic enclaves is associated with the origin of less evolved parental magmas erupted in the NCCA, such as those from La Poruña. In this case, the mafic enclaves would represent batches of less evolved magmas that ascended from deeper sources and probably contributed in the eruption of the dacitic domes. Renzulli et al., 2006. In XI Congreso Geol

  6. Devonian granitoids and their hosted mafic enclaves in the Gorny Altai terrane, northwestern Central Asian Orogenic Belt: crust-mantle interaction in a continental arc setting

    Science.gov (United States)

    Chen, Ming; Sun, Min

    2016-04-01

    Granitoids are a major component in the upper continental crust and hold key information on how did the continental crust grow and differentiate. This study focuses on the Yaloman intrusive complex from the Gorny Altai terrane, northwestern Central Asian Orogenic Belt (CAOB). The association of granitoids and mafic enclaves can provide important clues on the source nature, petrogenetic processes and geodynamic setting of the Yaloman intrusive complex, which in turn will shed light on the crustal evolution in the northwestern CAOB. Zircon U-Pb dating shows that the granitoids, including quartz diorites and granodiorites, were emplaced in ca. 389-387 Ma. The moderate Na2O + K2O contents and low A/CNK values indicate that these rocks belong to the sub-alkaline series with metaluminous to weakly peraluminous compositions. The granitoids yield two-stage zircon Hf model ages of ca. 0.79-1.07 Ga and whole-rock Nd model ages of ca. 0.90-0.99 Ga, respectively, implying that they were mainly sourced from Neoproterozoic juvenile crustal materials. The mafic enclaves show an almost identical crystallization age of ca. 389 Ma. The identification of coarse-grained xenocrysts and acicular apatites, together with the fine-grained texture, makes us infer that these enclaves are likely to represent magmatic globules commingled with the host magmas. The low SiO2 and high MgO contents of the mafic enclaves further suggest that substantial mantle-derived mafic melts were probably involved in their formation. Importantly, the SiO2 contents of the granitoids and mafic enclaves are well correlated with other major elements and most of the trace elements. Also a broadly negative correlation exists between the SiO2 contents and whole-rock epsilon Nd (390 Ma) values of the granitoids. Given the observation of reversely zoned plagioclases within the granitoids and the common occurrence of igneous mafic enclaves, we propose that magma mixing probably played an important role in the formation

  7. Formation of Cretaceous Cordilleran and post-orogenic granites and their microgranular enclaves from the Dalat zone, southern Vietnam: Tectonic implications for the evolution of Southeast Asia

    Science.gov (United States)

    Shellnutt, J. Gregory; Lan, Ching-Ying; Van Long, Trinh; Usuki, Tadashi; Yang, Huai-Jen; Mertzman, Stanley A.; Iizuka, Yoshi; Chung, Sun-Lin; Wang, Kuo-Lung; Hsu, Wen-Yu

    2013-12-01

    Cordilleran-type batholiths are useful in understanding the duration, cyclicity and tectonic evolution of continental margins. The Dalat zone of southern Vietnam preserves evidence of Late Mesozoic convergent zone magmatism superimposed on Precambrian rocks of the Indochina Block. The Dinhquan, Deoca and Ankroet plutons and their enclaves indicate that the Dalat zone transitioned from an active continental margin producing Cordilleran-type batholiths to highly extended crust producing within-plate plutons. The Deoca and Dinhquan plutons are compositionally similar to Cordilleran I-type granitic rocks and yield mean zircon U/Pb ages between 118 ± 1.4 Ma and 115 ± 1.2 Ma. Their Sr-Nd whole rock isotopes (ISr = 0.7044 to 0.7062; εNd(T) = - 2.4 to + 0.2) and zircon Hf isotopes (εHf(T) = + 8.2 ± 1.2 and + 6.4 ± 0.9) indicate that they were derived by mixing between a mantle component and an enriched component (i.e. GLOSS). The Ankroet pluton is chemically similar to post-orogenic/within-plate granitic rocks and has a zircon U/Pb age of 87 ± 1.6 Ma. Geobarometric calculations indicate that amphibole within the Ankroet pluton crystallized at a depth of ~ 6 kbar which is consistent with the somewhat more depleted Sr-Nd isotope (ISr = 0.7017 to 0.7111; εNd(T) = - 2.8 to + 0.6) and variable εHf(T) compositions suggesting a stronger influence of crustal material in the parental magma. The compositional change of the Dalat zone granitic rocks during the middle to late Cretaceous indicates that the tectonic regime evolved from a continental arc environment to one of post-orogenic extension. The appearance of sporadic post-90 Ma magmatism in the Dalat zone and along the eastern margin of Eurasian indicates that there was no subsequent orogenic event and the region was likely one of highly extended crust that facilitated the opening of the South China Sea during the latter half of the Cenozoic.

  8. Genesis of felsic plutonic magmas and their igneous enclaves

    DEFF Research Database (Denmark)

    Clemens, John D.; Maas, Roland; Waight, Tod Earle

    2016-01-01

    -type Pyalong pluton was emplaced, apparently along an east-west-orientated fracture zone. Around 367 Ma, the main I-type Baynton pluton intruded as numerous shallow-dipping sheets. The last plutonic event was the intrusion of the broad, thin, flat-lying, and crosscutting sheet of the I-type Beauvallet pluton...... the relatively high abundance of igneous-textured microgranular enclaves (MEs). The MEs show neither chemical nor isotope mixing trends with each other or with the host magmas. Variations in the Baynton magmas were derived from the heterogeneity of the source terrane, with individual magma batches formed from...

  9. Magma Mixing: Magmatic Enclaves in Morne Micotrin, Dominica

    Science.gov (United States)

    Hickernell, S.; Frey, H. M.; Manon, M. R. F.; Waters, L. E.

    2017-12-01

    Magmatic enclaves in volcanic rocks provide direct evidence of magma mingling/mixing within a magma reservoir and may reinvigorate the system and trigger eruption, as documented at the Soufriere Hills in Montserrat. Lava domes on the neighboring island of Dominica also contain multiple enclave populations and may be evidence for similar magma chamber processes. The central dome of Micotrin is at the head of the Roseau Valley, which was filled with 3 km3 of pyroclastic deposits from eruptions spanning 65 - 25 ka. There appear to be two distinct types of enclaves in the crystal-rich Micotrin andesites (60 wt% SiO2), fine-grained and coarse-grained. Fine-grained mafic enclaves (52 wt% SiO2) vary in size from 1 to 15 cm in diameter, whereas the coarse-grained enclaves are generally larger and range from 3-20 cm. Fine-grained enclaves are saturated in plag (35%) + opx (35%) + cpx (20%) + oxides (10%). Average pyroxenes are 0.01 to 0.02 cm in size, whereas plagioclase averages 0.05 cm and up to 0.1 cm. The texture of the fine-grained enclaves is cumulate-like, devoid of microlites and matrix glass. Coarse-grained enclaves lack cpx and have different modal abundances and textures: plag (75%) + opx (10%) + oxides (5%) + plag microlites (10%). Plagioclase are 0.1 cm in size and orthopyroxenes average 0.05 cm. The coarse-grained enclaves are highly vesicular, a notable difference from the host as well as the fine-grained enclaves. The boundaries of both the fine- and coarse-grained enclaves are quite sharp and distinct and there do not appear to be enclave minerals disaggregated in the host rock. Temperatures were determined by two oxides. The fine-grained enclaves had two populations of magnetite, yielding 847 + 21° and 920 + 17°C. The coarse-grained enclave was 890 + 42 °C, but the oxides were extensively exsolved. Plagioclase composition in both coarse and fine-grained samples was comparable, ranging from An50 to An80. Despite compositional similarity the textures of

  10. Secure Virtual Enclaves

    National Research Council Canada - National Science Library

    Shands, Deborah

    2002-01-01

    The Secure Virtual Enclaves (SVE) collaboration infrastructure allows multiple organizations to share their distributed application resources, while respecting organizational autonomy over local resources...

  11. Investigation of Microgranular Adsorptive Filtration System

    Science.gov (United States)

    Cai, Zhenxiao

    Over the past few decades, enormous advances have been made in the application of low-pressure membrane filtration to both drinking water and wastewater treatment. Nevertheless, the full potential of this technology has not been reached, due primarily to limitations imposed by membrane fouling. In drinking water treatment, much of the fouling is caused by soluble and particulate natural organic matter (NOM). Efforts to overcome the problem have focused on removal of NOM from the feed solution, usually by addition of conventional coagulants like alum and ferric chloride (FeCl3) or adsorbents like powdered activated carbon (PAC). While coagulants and adsorbents can remove a portion of the NOM, their performance with respect to fouling control has been inconsistent, often reducing fouling but sometimes having no effect or even exacerbating fouling. This research investigated microgranular adsorptive filtration (muGAF), a process that combines three existing technologies---granular media filtration, packed bed adsorption, and membrane filtration---in a novel way to reduce membrane fouling while simultaneously removing NOM from water. In this technology, a thin layer of micron-sized adsorbent particles is deposited on the membrane prior to delivering the feed to the system. The research reported here represents the first systematic study of muGAF, and the results demonstrate the promising potential of this process. A new, aluminum-oxide-based adsorbent---heated aluminum oxide particles (HAOPs)---was synthesized and shown to be very effective for NOM removal as well as fouling reduction in muGAF systems. muGAF has also been demonstrated to work well with powdered activated carbon (PAC) as the adsorbent, but not as well as when HAOPs are used; the process has also been successful when used with several different membrane types and configurations. Experiments using a wide range of operational parameters and several analytical tools lead to the conclusion that the fouling

  12. Woodpecker-inspired shock isolation by microgranular bed

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Sang-Hee [Department of Mechanical Engineering, University of California, Berkeley, CA 94720 (United States); Roh, Jin-Eep; Kim, Ki Lyug, E-mail: shyoon@me.berkeley.ed [Agency for Defense Development, Yuseong PO Box 35, Daejeon 305-600 (Korea, Republic of)

    2009-02-07

    This paper presents a woodpecker-inspired shock isolation (SI) using a microgranular bed to protect micromachined electronic devices (MEDs) for high-g military applications where mechanical excitations reach up to tens of thousands of gs and several hundreds of kHz. The shock isolating phenomenon in the microgranular bed within a metal housing, biomimetically inspired from a spongy bone within a skull of the woodpecker, controls unwanted high-frequency mechanical excitations so that their adverse effects on the embedded MEDs are kept within acceptable limit. The microgranular bed composed of close-packed microglass beads reduces the mechanical excitations transmitted to the MEDs through kinetic energy absorption. Two kinds of tests, a laboratory test and a 60 mm air-gun test, have been made. The laboratory test using a vibration exciter up to 25 kHz has demonstrated that the cut-off frequency (2.2-15.8 kHz) and roll-off steepness (-155.0 to -78.7 dB decade{sup -1}) are inversely proportional to the diameter of the close-packed microglass beads (68-875 {mu}m), whereas the vibration absorptivity (0.23-0.87) is proportional. The 60 mm air-gun test under high-g environments of up to 60 000 g has verified that the woodpecker-inspired SI is superior in improving the shock survivability of the MEDs to the conventional one using hard resin.

  13. Ethnic Enclaves and Immigrant Labour Market Outcomes

    DEFF Research Database (Denmark)

    Damm, Anna Piil

    This study investigates empirically how residence in ethnic enclaves affects labour market outcomes of refugees. Self-selection into ethnic enclaves in terms of unobservable characteristics is taken into account by exploitation of a Danish spatial dispersal policy which randomly disperses new...... refugees across locations conditional on six individual-specific characteristics. The results show that refugees with unfavourable unobserved characteristics are found to self-select into ethnic enclaves. Furthermore, taking account of negative self-selection, a relative standard deviation increase...

  14. La deliberación de enclave

    DEFF Research Database (Denmark)

    Agustin, Oscar Garcia

    2006-01-01

    La configuración de la esfera pública puede ampliarse a través de los distintos mecanismos de deliberación que ofrece Internet. De este modo, desde los enclaves deliberativos, opiniones extremas pueden entrar en debate con otras opiniones vertidas desde otros enclaves y espacios más generales. En...

  15. From Enclave to Linkage Economies?

    DEFF Research Database (Denmark)

    Hansen, Michael W.

    as the enclave economy par excellence, moving in with fully integrated value chains, extracting resources and exporting them as commodities having virtually no linkages to the local economy. However, new opportunities for promoting linkages are offered by changing business strategies of local African enterprises...... as well as foreign multinational corporations (MNCs). MNCs in extractives are increasingly seeking local linkages as part of their efficiency, risk, and asset-seeking strategies, and linkage programmes are becoming integral elements in many MNCs’ corporate social responsibility (CSR) activities....... At the same time, local African enterprises are eager to, and increasingly capable of, linking up to the foreign investors in order to expand their activities and acquire technology, skills and market access. The changing strategies of MNCs and the improving capabilities of African enterprises offer new...

  16. Ethnic Enclaves and Immigrant Labor Market Outcomes

    DEFF Research Database (Denmark)

    Damm, Anna Piil

    2009-01-01

    increase in the ethnic enclave size increases annual earnings by 18 percent on average, irrespective of skill level. Third, the paper proposes an explanation for the earnings gain of ethnic enclave members. Enclave members benefit from more access to ethnic networks because ethnic networks disseminate job...

  17. Late Neoproterozoic layered mafic intrusion of arc-affinity in the Arabian-Nubian Shield: A case study from the Shahira layered mafic intrusion, southern Sinai, Egypt

    Energy Technology Data Exchange (ETDEWEB)

    Azer, M.K.; Obeid, M.A.; Gahalan, H.A.

    2016-07-01

    The Shahira Layered Mafic Intrusion (SLMI), which belongs to the late Neoproterozoic plutonic rocks of the Arabian-Nubian Shield, is the largest layered mafic intrusion in southern Sinai. Field relations indicate that it is younger than the surrounding metamorphic rocks and older than the post-orogenic granites. Based on variation in mineral paragenesis and chemical composition, the SLMI is distinguished into pyroxene-hornblende gabbro, hornblende gabbro and diorite lithologies. The outer zone of the mafic intrusion is characterized by fine-grained rocks (chilled margin gabbroic facies), with typical subophitic and/or microgranular textures. Different rock units from the mafic intrusion show gradational boundaries in between. They show some indications of low grade metamorphism, where primary minerals are transformed into secondary ones. Geochemically, the Shahira layered mafic intrusion is characterized by enrichment in LILE relative to HFSE (e.g. Nb, P, Zr, Ti, Y), and LREE relative to HREE [(La/Lu)n= 4.75–8.58], with subalkaline characters. It has geochemical characteristics of pre-collisional arc-type environment. The geochemical signature of the investigated gabbros indicates partial melting of mantle wedge in a volcanic-arc setting, being followed by fractional crystallization and crustal contamination. Fractional crystallization processes played a vital role during emplacement of the Shahira intrusion and evolution of its mafic and intermediate rock units. The initial magma was evolved through crystallization of hornblende which was caused by slight increasing of H2O in the magma after crystallization of liquidus olivine, pyroxene and Ca-rich plagioclase. The gabbroic rocks crystallized at pressures between 4.5 and 6.9kbar (~15–20km depth). Whereas, the diorites yielded the lowest crystallization pressure between 1.0 to 4.4Kbar (<10km depth). Temperature was estimated by several geothermometers, which yielded crystallization temperatures ranging from 835

  18. Petrochemical and Sr-Nd isotope investigations of Cretaceous intrusive rocks and their enclaves in the Togouchi-Yoshiwa district, northwest Hiroshima prefecture, SW Japan

    International Nuclear Information System (INIS)

    Ishioka, Jun; Iizumi, Shigeru

    2003-01-01

    Petrographic, petrochemical and Sr-Nd isotopic data are presented for granitoids and microdioritic enclaves from two Cretaceous stocks (Togouchi granodiorite and Tateiwayama granite porphyry) from the Togouchi-Yoshiwa district, northwest Hiroshima prefecture, SW Japan. The data are used to examine the genetic relationships between the microdioritic enclaves and their granitoid hosts. The granodiorite, granite porphyry and the microdioritic enclaves are all calc-alkaline in nature, and belong to the I-type ilmenite series. The Togouchi graniodiorite has a Rb-Sr whole rock isochron age of 85.6±4.7 Ma with an initial Sr isotope ratio (SrI) of 0.70634±0.00012 (2σ). The Tateiwayama granite porphyry has a slightly younger Rb-Sr whole isochron age (77.4±3.1 Ma) but similar SrI of 0.70653±0.00015, suggesting that both stocks may have been derived from the same source. Despite diverse whole rock chemistry, the microdioritic enclaves in the respective intrusives have quite similar initial Sr and Nd isotope ratios, suggesting that they formed by fractional crystallization of a single magma, and also that the source of the enclaves in both intrusives had similar geochemical characteristics. In both stocks, however, the enclaves have distinctly lower initial Sr isotope ratios than their respective host rocks, indicating that they were derived from a different source than their hosts. In view of the geochemical and Sr-Nd isotope data, we infer that the enclave magmas were derived from a similar LILE- and LREE-enriched source to that of the Cretaceous basalts and gabbroic-dioritic rocks that are sporadically distributed in SW Japan. Such mafic to intermediate magmas were probably derived from the upper mantle, and transferred both heat and material to the lower crust, thus producing granitic magmas by partial melting. Successive mafic magmas or their differentiates could then have been injected into the granitic magma chamber, trapped and quenched, resulting in the formation

  19. The Study of enclaves and relative age of plutonic bodies in the Alvand Plutonic complex

    International Nuclear Information System (INIS)

    Sepahi Gerow, A. A.; Moien-Vaziri, H.

    2000-01-01

    The study of enclaves and field observations indicate that: The Alvand plutonic complex comprise several plutonic phases with sharp contact and different ages. The older plutonic rocks are composed of gabbro, diorite and tonalites. The porphyroid granites were formed at least in two phases and they are younger than gabbros, diorites and tonalites. The hololeucocratic granitoids were also formed in two phases and they are the youngest plutonic phase in the Alvand plutonic complex. The granitic rocks are magmatic and they are not metasomatic in origin. The porphyroid granites (monzogranites and granodiorites) are S-type (Anatexites). According to radiometric ages and relative ages we believe that mafic plutonism have occurred during pre-middle Cretaceous to Paleocene ages and felsic plutonism have occurred during middle Cretaceouc to Paleocene ages

  20. The "Technical and Vocational Education Initiative": Enclaves in British Schools.

    Science.gov (United States)

    Saunders, Murray

    The Technical and Vocational Education Initiative (TVEI) is intended as a pilot, on a massive scale, of particular approaches, with a systematic need to identify TVEI effects on students, staff, resources, and curricula. TVEI has a strong tendency toward the development of pilot enclaves in terms of its administrative, curricular,…

  1. Early Cretaceous Na-rich granitoids and their enclaves in the Tengchong Block, SW China: Magmatism in relation to subduction of the Bangong-Nujiang Tethys ocean

    Science.gov (United States)

    Zhu, Ren-Zhi; Lai, Shao-Cong; Santosh, M.; Qin, Jiang-Feng; Zhao, Shao-Wei

    2017-08-01

    The Na-rich intermediate-to-felsic granitic rocks provide insights into the generation of magmas in subduction zones. This paper presents zircon LA-ICP-MS U-Pb ages as well as whole-rock geochemical, mineral chemical, and in situ zircon Hf isotopic data on Na-rich granitic rocks from the Tengchong Block, SW China. The granodiorites and associated mafic magmatic enclaves (MMEs) from the Menglian batholith yield zircon U-Pb ages of 116.1 ± 0.8 to 117.8 ± 0.6 Ma and 117.7 ± 0.7 Ma, respectively. Both host granodiorites and enclaves show calc-alkaline and sodium-rich nature, enrichment in large-ion lithophile elements (LILEs), and variable depletion in zircon Hf isotopic compositions. Euhedral amphiboles in both granodiorites and associated enclaves are magnesian-hornblende with high Mg and Ca and contain euhedral plagioclase inclusions of labradorite to andesine (An36-57) composition. The granodiorite was most likely derived through the mixing of partial melts derived from juvenile basaltic lower crust and a minor evolved component of ancient crustal sources. The quartz monzodiorite-granodiorites and associated MMEs from the Xiaotang-Mangdong batholith yield zircon U-Pb ages of 120.3 ± 1.3 to 122.6 ± 0.8 Ma and 120.7 ± 1.5 Ma. These rocks are also sodium-rich and show calc-alkaline trend with negative zircon Hf isotopic compositions (- 5.55 to + 0.58). The MMEs in the host intrusions are monzogabbro with variable and depleted zircon Hf isotopic compositions. The amphiboles in the both host intrusions and the enclaves show Al-rich ferro-tschermakite composition. We infer that the quartz monzodiorite-granodiorites were derived from magmas generated by the melting of ancient basaltic rocks in the lower arc crust induced by the underplating of mantle-derived mafic magmas. The formation of the different types of Na-rich granitic rocks is correlated to the subduction of Bangong-Nujiang Tethyan ocean. A comparison with magmatism in the northern magmatic belt suggests

  2. Short-term evaluation of non-absorbable microgranular hydroxyapatite infiltration in the guinea pig subepidermal abdominal region

    Directory of Open Access Journals (Sweden)

    A.P. Xavier

    2002-01-01

    Full Text Available Non-absorbable microgranular hydroxyapatite was infiltrated into the subepidermal abdominal region of guinea pigs in order to assess the possibility of using this material to correct deficiencies in orbital volume. Microgranular hydroxyapatite (2.0 ml was subepidermally infiltrated into the abdominal region of 20 guinea pigs. The animals were divided into four experimental groups of 5 animals each, which were killed 7 (G1, 15 (G2, 30 (G3 and 60 (G4 days after infiltration. The area and the largest and smallest diameters of the nodules formed by infiltration were evaluated at the site of infiltration and histological examination was performed. The mean granuloma area was similar in all groups. Histopathological examination showed that the material remained isolated from surrounding tissues by a pseudocapsule that became denser throughout the experiment. A host reaction started with young fibroblastic tissue that evolved to dense tissue until cartilaginous tissue was formed in G4, progressively advancing towards the center of the granuloma from G1 to G4. Non-absorbable microgranular hydroxyapatite is an inert material that was well tolerated by the animals studied, with maintenance of the infiltrated volume, and may perhaps be useful to fill anophthalmic cavities.

  3. Mafic-silicic magma interaction in the layered 1.87 Ga Soukkio Complex in Mäntsälä, southern Finland

    Directory of Open Access Journals (Sweden)

    Toni T. Eerola

    2002-01-01

    Full Text Available The Svecofennian layered Soukkio Complex (1.87 Ga in Mäntsälä, southern Finland, consists of layered tholeiitic gabbro and porphyritic calc-alkaline monzonite, quartz monzonite and granite, mingled together. The gabbro belongs to a group of ten mafic-ultramafic intrusions of Mäntsälä, part of the 150 km long and 20 km wide, linear, E-W trending Hyvinkää–Mäntsälä Gabbroic Belt(HMGB, representing syn-collisional magmatism. Structures and textures related to magma mingling and mixing occur in a 1–2 km wide zone around Lake Kilpijärvi, located at the center of the Soukkio Complex. The complex is compositionally stratified and consists of four zones:its base, found at the Western Zone, is a dynamically layered gabbro. The followingtonalite is probably a result of magma mixing. Felsic amoeboid layers and pipes, alternating with or cutting the fine-grained gabbro in the Central-Western Zone, resemble those of mafic-silicic layered intrusions in general. Mafic magmatic enclaves (MMEs and pillows form the South-Central Zone and disrupted synplutonic mafic dykes or sheets intruded the granite in the Eastern Zone. The MMEs and disrupted synplutonic mafic dykes or sheets show cuspate and chilled margins against the felsic host, quartz ocelli, corroded K-feldspar xenocrysts with or without plagioclase mantles, and acicular apatite, all typical features of magma mingling and mixing. Mixing is suggested by intermediate composition of MMEs between granitoid and gabbro, as well as by their partly linear trends in some Harker diagrams. REE composition of the MMEs is similar to that of the Soukkio Gabbro, as expected for granite hosted MMEs. The model proposed for evolution of the Soukkio Complex involves intrusion of mafic magma into the crust, causing its partial melting. This generated granitic magma above the mafic chamber. Injections of mafic magma invaded the felsic chamber and those magmas interacted mainly by intermingling. Mingling and

  4. Secure Enclaves: An Isolation-centric Approach for Creating Secure High Performance Computing Environments

    Energy Technology Data Exchange (ETDEWEB)

    Aderholdt, Ferrol [Tennessee Technological Univ., Cookeville, TN (United States); Caldwell, Blake A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hicks, Susan Elaine [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Koch, Scott M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Naughton, III, Thomas J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Pelfrey, Daniel S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Pogge, James R [Tennessee Technological Univ., Cookeville, TN (United States); Scott, Stephen L [Tennessee Technological Univ., Cookeville, TN (United States); Shipman, Galen M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Sorrillo, Lawrence [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-01-01

    High performance computing environments are often used for a wide variety of workloads ranging from simulation, data transformation and analysis, and complex workflows to name just a few. These systems may process data at various security levels but in so doing are often enclaved at the highest security posture. This approach places significant restrictions on the users of the system even when processing data at a lower security level and exposes data at higher levels of confidentiality to a much broader population than otherwise necessary. The traditional approach of isolation, while effective in establishing security enclaves poses significant challenges for the use of shared infrastructure in HPC environments. This report details current state-of-the-art in virtualization, reconfigurable network enclaving via Software Defined Networking (SDN), and storage architectures and bridging techniques for creating secure enclaves in HPC environments.

  5. Peer-to-Peer Enclaves for Improving Network Defence

    Directory of Open Access Journals (Sweden)

    David W. Archer

    2013-07-01

    Full Text Available Information about cyberthreats within networks spreads slowly relative to the speed at which those threats spread. Typical "threat feeds" that are commercially available also disseminate information slowly relative to the propagation speed of attacks, and they often convey irrelevant information about imminent threats. As a result, hosts sharing a network may miss opportunities to improve their defence postures against imminent attack because needed information arrives too late or is lost in irrelevant noise. We envision timely, relevant peer-to-peer sharing of threat information – based on current technologies – as a solution to these problems and as a useful design pattern for defensive cyberwarfare. In our setting, network nodes form communities that we call enclaves, where each node defends itself while sharing information on imminent threats with peers that have similar threat exposure. In this article, we present our vision for this solution. We sketch the architecture of a typical node in such a network and how it might interact with a framework for sharing threat information; we explain why certain defensive countermeasures may work better in our setting; we discuss current tools that could be used as components in our vision; and we describe opportunities for future research and development.

  6. Constraints on aeolian sediment transport to foredunes within an undeveloped backshore enclave on a developed coast

    Science.gov (United States)

    Kaplan, Kayla L.; Nordstrom, Karl F.; Jackson, Nancy L.

    2016-10-01

    Landforms present in undeveloped beach enclaves located between properties developed with houses and infrastructure are often left to evolve naturally but are influenced by the human structures near them. This field study evaluates how buildings and sand-trapping fences change the direction of wind approach, reduce wind speed, and restrict fetch distances for sediment entrainment, thereby reducing the potential for aeolian transport and development of dunes in enclaves. Field data were gathered in an 80 m long, 44 m deep beach enclave on the ocean shoreline of New Jersey, USA. Comparison of wind characteristics in the enclave with a site unaffected by buildings revealed that offshore winds in the enclave are reduced in strength and altered in direction by landward houses, increasing the relative importance of longshore winds. Vertical arrays of anemometers on the foredune crest, foredune toe and berm crest in the enclave revealed increasing wind speed with distance offshore, with strongest winds on the berm crest. Vertical cylindrical traps on the foredune crest, foredune toe, mid-backshore, berm crest and upper foreshore revealed the greatest rate of sediment transport on the berm crest. Sediment samples from the beach and from traps revealed limited potential for aeolian transport because of coarse grain sizes. Strong oblique onshore winds are common in this region and are normally important for transporting sand to dunes. The length of an enclave and the setback distance on its landward side determine the degree to which sediment delivered by oblique winds contributes to dune growth. The landward edge of the enclave (defined by a sand fence near the dune toe) is sheltered along its entire length from winds blowing at an angle to the shoreline of 25° or less. A foredune set back this distance in an enclave the length of an individual lot (about 20 m) would be sheltered at an angle of 57° or less, reducing the opportunity for dune building by onshore winds

  7. Ethnic enclaves and risk of psychiatric disorders among first- and second-generation immigrants in Sweden.

    Science.gov (United States)

    Mezuk, Briana; Li, Xinjun; Cederin, Klas; Concha, Jeannie; Kendler, Kenneth S; Sundquist, Jan; Sundquist, Kristina

    2015-11-01

    Some non-Western immigrant groups in Europe have elevated risk of psychosis relative to native-born. It is hypothesized that neighborhood ethnic density moderates this risk. Immigration to Sweden has increased substantially recently, particularly from the Middle East. This study examined the relationship between neighborhood ethnic density (i.e., living in an immigrant enclave) and risk of psychotic and affective disorders among three groups: Iraqi immigrants, immigrants from other nations, and native-born Swedes. Individuals aged 15-60, without prevalent psychopathology, were drawn from Swedish population-based registries and followed from 2005 to 2010 (N = 950,979). Multi-level logistic regression was used to examine the association between neighborhood ethnic composition and incident psychopathology. Cumulative incidence of psychopathology was greater in Iraqi enclaves relative to predominantly Swedish neighborhoods (6.3 vs. 4.5%). Iraqis living in enclaves did not have significantly greater risk of psychosis (Odds Ratio (OR): 1.66, 95% Confidence Interval (CI) 0.92-2.97) or affective disorders (OR: 1.04, 95%CI 0.85-1.27) relative to those in predominantly Swedish neighborhoods. There was no increased risk of psychosis (OR: 0.93, p > 0.05) or affective disorders (OR: 0.93, p > 0.05) for other immigrants living in an enclave. Swedes living in an enclave had elevated risk of both psychosis (OR: 1.37, p immigrants in Sweden. Findings regarding Swedes are consistent with social drift.

  8. Research of consumers’ attitudes on the organic food consumption in the Serbian enclaves in Kosovo

    Directory of Open Access Journals (Sweden)

    Maksimović Goran

    2017-01-01

    Full Text Available The organic production in Serbian enclaves in Kosovo has a great potential based on the extensive production mostly in hilly-mountainous areas with rich and convenient environment for the organic production of medicinal plants, fruits, vegetables, wine, honey etc., but it still keeps developing. The enclave can realise a high income, and thereby also an economic basis for the sustainable development of multifunctional agricultural holdings in Serbian enclaves, by the production and sale of organic products on local markets. In this paper, the authors study the consumers’ attitudes on purchase and consumption of organic food in Serbian enclaves in Kosovo. Empirical research was carried out on a spatial sample of 300 respondents, by a personal communication technique using the questionnaire as an instrument of research method. Areas of research are towns: Northern Kosovska Mitrovica, Leposavic, Zubin Potok and Gracanica. Goal of the research is to discover the preferences, motives, attitudes and interests of consumers for buying the organic products, based on a defined survey to recognise the basic features of supply and the demand of organic agricultural and food products. After analysing the conducted survey, we have discovered that the organic food market in Serbian enclaves in Kosovo has not been sufficiently developed; it is necessary to expand the range of organic agriculture products and a constant supply is required, better marketing, and better information and education of consumers in order to raise supply to a higher level.

  9. Impact of socioeconomic status and ethnic enclave on cervical cancer incidence among Hispanics and Asians in California.

    Science.gov (United States)

    Froment, Marie-Anne; Gomez, Scarlett L; Roux, Audrey; DeRouen, Mindy C; Kidd, Elizabeth A

    2014-06-01

    This study aimed to evaluate the incidence of cervical cancer by nativity [United States (US) versus non-US], neighborhood socioeconomic status and ethnic enclave among Hispanics and Asians in California. Using data from the California Cancer Registry, information on all primary invasive cervical cancer (Cca) patients diagnosed in California from January 1, 1990 through December 31, 2004 was obtained. We analyzed the influence of enclave, socioeconomic status and nativity on Cca incidence. Among the 22,189 Cca cases diagnosed between 1990 and 2004, 50% were non-Hispanic white, 39% Hispanic and 11% Asian women, and 63% US-born. Seventy percent of the Cca cases were squamous cell carcinoma, 19% adenocarcinoma and 11% other histologies. Higher incidence of Cca was observed in high enclave (76%) and low socioeconomic status (70%) neighborhoods. By ethnic group, US-born women showed lower rates of squamous cell carcinoma compared to foreign-born women. Hispanics living in low socioeconomic and high enclave had 12.7 times higher rate of Cca than those living in high socioeconomic, low enclave neighborhoods. For Asian women incidence rates were 6 times higher in the low socioeconomic, high enclave neighborhoods compared to those living in high socioeconomic, low enclave neighborhoods. More targeted outreach to increase Pap smear screening and human papilloma virus vaccination for women living in high enclave neighborhoods can help decrease the incidence of Cca in these groups of women. Copyright © 2014 Elsevier Inc. All rights reserved.

  10. Historias transnacionales: nuevas interpretaciones de los enclaves en América Latina

    Directory of Open Access Journals (Sweden)

    Catherine LeGrand

    2006-01-01

    Full Text Available Este ensayo revisa las nuevas direcciones en la investigación sobre ¿enclaves extranjeros¿ en América Latina, centrándose particularmente en las regiones bananeras de la United Fruit Company (UFCO en el Caribe y Centroamérica. Explora las preguntas y aproximaciones que orientan la ¿nueva historia de los enclaves¿ producida en universidades norteamericanas en los últimos quince años, las críticas que han surgido a dichos estudios y el giro contemporáneo en la mirada a las luchas por los recursos naturales.

  11. The Malay Enclave of Kampong Bharu as a Living Tradition: A place of uncertainty

    Directory of Open Access Journals (Sweden)

    Norsidah Ujang

    2016-06-01

    Full Text Available In the case of Asian cities, poor redevelopment process has often resulted in the loss of historic urban fabric. Kampong Bharu is a traditional Malay settlement in the heart of the Kuala Lumpur city, holds a unique case of a struggle to preserve its local identity. This paper reviews the scenario regarding the enclave in light of the current redevelopment proposal. Reviews of literature and analysis of recent reports indicated that the future of the enclave is in the state of uncertainty. People oriented planning based upon a deep understanding of culture and tradition could bring about a natural approach towards a definitive redevelopment initiatives.

  12. Petrology and oxygen isotope geochemistry of the Pucon ignimbrite - Southern Andean volcanic zone, Chile: Implications for genesis of mafic ignimbrites

    International Nuclear Information System (INIS)

    McCurry, Michael; Schmidt, Keegan

    2001-01-01

    eruptions were originally dissolved within in the pre-PI magma. They document an important repeating pattern between chemically evolved compositions and explosive eruptions at Volcan Villarrica that is particularly prominent in the cases of the two largest ignimbrite-forming eruptions. They infer that the precursor magma chamber became compositionally stratified through time, with the most evolved, volatile rich magma accumulating towards the top of the chambers, and culminating in voluminous mafic ignimbrite eruptions. In this study we characterize petrologic, geochemical and oxygen isotope characteristics of magmatic pyroclasts from the Pucon Ignimbrite, and one accidental granitoid lithic, extending on the previous work by Clavero (1996) and Lopez-Escobar and Moreno (1995). We critically evaluate previous models, and combine ours and previous data to constrain and develop an alternate petrogenetic model of magmatic evolution of the pre-PI magma chamber, focusing on possible sources of volatiles derived from country rocks and from processes operating within the original magma chamber. We also document the occurrence of a previously unidentified, dacitic, magmatic enclave component of the ignimbrite (au)

  13. A Comparative Perspective on the Ethnic Enclave: Blacks, Italians, and Jews in New York City.

    Science.gov (United States)

    Model, Suzanne

    1985-01-01

    Research among workers and entrepreneurs in three ethnic groups found that (1) ethnic employees in an enclave environment receive rewards in some ways superior to those available to their counterparts in the secondary sectors, and (2) special linkages exist between ethnic businesses that facilitate the prosperity of these companies in the…

  14. Pseudotachylitic breccia in mafic and felsic rocks

    Science.gov (United States)

    Kovaleva, Elizaveta; Huber, Matthew S.

    2017-04-01

    Impact-produced pseudotachylitic breccia (PTB) is abundant in the core of the Vredefort impact structure and was found in many pre-impact lithologies (e.g., Reimold and Colliston, 1994; Gibson et al., 1997). The mechanisms involved in the process of forming this rock remain highly debated, and various authors have discussed many possible models. We investigate PTB from two different rock types: meta-granite and meta-gabbro and test how lithology controls the development of PTB. We also report on clast transport between different lithologies. In the core of the Vredefort impact structure, meta-granite and meta-gabbro are observed in contact with each other, with an extensive set of PTB veins cutting through both lithologies. Microstructural analyses of the PTB veins in thin sections reveals differences between PTBs in meta-granite and meta-gabbro. In granitic samples, PTB often develops along contacts of material with different physical properties, such as a contact with a migmatite or pegmatite vein. Nucleation sites of PTB have features consistent with ductile deformation and shearing, such as sigmoudal-shaped clasts and dragged edges of the veins. Preferential melting of mafic and hydrous minerals takes place (e.g., Reimold and Colliston, 1994; Gibson et al., 2002). Refractory phases remain in the melt as clasts and form reaction rims. In contrast, PTB in meta-gabbro develop in zones with brittle deformation, and do not exploit existing physical contacts. Cataclastic zones develop along the faults and progressively produce ultracataclasites and melt. Thus, PTB veins in meta-gabbro contain fewer clasts. Clasts usually represent multi-phase fragments of host rock and not specific phases. Such fragments often originate from the material trapped between two parallel or horse-tail faults. The lithological control on the development of PTB does not imply that PTB develops independently in different lithologies. We have observed granitic clasts within PTB veins in meta

  15. Microgranular variant of acute promyelocytic leukemia with der(17) ins(17;15): A case report and review of the literature

    Science.gov (United States)

    GUAN, HONGZAI; LIU, JING; GUO, XIAOFANG; WU, CHUNMEI; YU, HUAWEI

    2015-01-01

    Acute promyelocytic leukemia (APL) with variant translocations is rare. The patient of the present case report, a 2-year-old male with a microgranular variant of APL carrying der(17) ins(17;15) translocation, exhibited fever and epistaxis. The complete blood count showed marked leukocytosis with 72% atypical promyelocytes, anemia and thrombocytopenia. Conventional cytogenetic analysis of the bone marrow cells revealed a karyotype of 47, XY, add(3)(q29), −7, ins(17;15)(q12;q14q22),+21,+mar. The promyelocytic leukemia/retinoic acid receptor α (PML/RARα) rearrangement and insertion were confirmed by fluorescence in situ hybridization. The PML/RARα transcripts were not detected by the reverse transcription polymerase chain reaction, and the patient was diagnosed with microgranular variant M3 APL. The patient achieved remission after a 30-day treatment and was still in remission during a recent follow-up. The present findings suggest that the ins(17;15) variant in APL may not be associated with an unfavorable prognosis. In summary, we reported an extremely rare case of APL with der(17) ins(17;15) abnormality in a pediatric patient and reviewed the literature. PMID:26622430

  16. Interaction of coeval felsic and mafic magmas from the Kanker ...

    Indian Academy of Sciences (India)

    66

    20 crystallization of the latter, results in hybrid magmas under the influence of thermal and. 21 chemical exchange. The mechanical exchange occurs between the coexisting magmas due to. 22 viscosity contrast, if the mafic magma enters slightly later into the magma chamber, when the. 23 felsic magma started to crystallize.

  17. Mafic dykes at the southwestern margin of Eastern Ghats belt ...

    Indian Academy of Sciences (India)

    Ghats belt: Evidence of rifting and collision. S Bhattacharya. 1,∗ ... 1.3 Ga, which may have been initiated by intra-plate volcanism. 1. Introduction ... tively, is described as a compressional orogen. Keywords. ... charnockite gneiss, around Naraseraopet, AP (b) Thin mafic ... Sometimes orthopyroxene also occurs at margin of.

  18. Minority Status and Labor Market Outcomes : Does India Have Minority Enclaves?

    OpenAIRE

    Das, Maitreyi Bordia

    2008-01-01

    This paper uses data from the 61st Round of the National Sample Survey to understand the employment outcomes of Dalit and Muslim men in India. It uses a conceptual framework developed for the US labor market that states that ethnic minorities skirt discrimination in the primary labor market to build successful self-employed ventures in the form of ethnic enclaves or ethnic labor markets. ...

  19. Immigrant Arab adolescents in ethnic enclaves: physical and phenomenological contexts of identity negotiation.

    Science.gov (United States)

    Kumar, Revathy; Seay, Nancy; Karabenick, Stuart A

    2015-04-01

    Ecologically embedded social identity theories were used to examine the risk and protective factors associated with the identity negotiation and adjustment of recent immigrant Arab (IA) adolescents to the United States residing in ethnic enclaves. Yemeni, Lebanese, and Iraqi 8th-graders (n = 45) from 4 ethnic enclave schools participated in focus-group interviews. In-depth analyses of interviews revealed that living in an ethnic enclave enhanced IA adolescents' feelings of belonging to the community. However, the new immigrant status coupled with country of origin determined the permeability of intergroup boundaries with well-established Arab and Arab American peers. Their identity negotiations and social identity salience (national, religious, and pan-Arab) were informed by transitional experiences from home to host country and the prevailing political and cultural tensions between the two, recognition of national hierarchy within the Arab community, perceptions of discrimination by the larger society, changed educational aspirations consequent to immigration, and current physical (school and community) and phenomenological contexts. Findings suggest that current theoretical perspectives should be extended to incorporate phenomenological representations of past spaces and places not currently occupied to understand adolescents' multifaceted identity. (c) 2015 APA, all rights reserved).

  20. Formación de un enclave transnacional en la ciudad de Santiago de Chile

    Directory of Open Access Journals (Sweden)

    Carolina Stefoni

    2013-01-01

    Full Text Available La llegada de inmigrantes a Chile ha transformado distintos lugares de Santiago, siendo un caso emblemático el sector de Plaza de Armas, centro histórico de la ciudad aquí analizado. Se sostiene que la concentración de actividades comerciales y prácticas cotidianas de los migrantes configuran un enclave transnacional. El objetivo del artículo es ofrecer un modelo de análisis que permita reconocer, describir y comprender el carácter transnacional que puede adquirir un espacio como el que se encuentra en la ciudad de Santiago. Utilizando el caso de los cibercafés emplazados dentro del enclave, se analizarán las prácticas y relaciones sociales, así como las materialidades que circulan y se desarrollan de manera transfronteriza. El objetivo es analizar cómo estas tres dimensiones configuran un modo de habitar que logra construir el carácter transnacional que adquiere el enclave.

  1. A warm thermal enclave in the late Pleistocene of the south-eastern United States.

    Science.gov (United States)

    Russell, Dale A; Rich, Fredrick J; Schneider, Vincent; Lynch-Stieglitz, Jean

    2009-05-01

    Physical and biological evidence supports the probable existence of an enclave of relatively warm climate located between the Southern Appalachian Mountains and the Atlantic Ocean in the United States during the Last Glacial Maximum. The region supported a mosaic of forest and prairie habitats inhabited by a "Floridian" ice-age biota. Plant and vertebrate remains suggest an ecological gradient towards Cape Hatteras (35 degreesN) wherein forests tended to replace prairies, and browsing proboscideans tended to replace grazing proboscideans. Beyond 35 degreesN, warm waters of the Gulf Stream were deflected towards the central Atlantic, and a cold-facies biota replaced "Floridian" biota on the Atlantic coastal plain. Because of niche diversity and relatively benign climate, biodiversity may have been greater in the south-eastern thermal enclave than in other unglaciated areas of North America. However, the impact of terminal Pleistocene megafaunal extinctions may also have been shorter and more severe in the enclave than further north. A comparison with biotic changes that occurred in North America approximately 55 million years (ma) ago at the Paleocene-Eocene Thermal Maximum suggests that similar processes of change took place under both ice-house and greenhouse climates.

  2. The Jeffers Brook diorite-granodiorite pluton: style of emplacement and role of volatiles at various crustal levels in Avalonian appinites, Canadian Appalachians

    Science.gov (United States)

    Pe-Piper, Georgia; Piper, David J. W.

    2018-04-01

    Small appinite plutons ca. 610 Ma outcrop in the peri-Gondwanan Avalon terrane of northern Nova Scotia, with different structural levels exposed. Field mapping shows that the Jeffers Brook pluton is a laccolith emplaced along an upper crustal thrust zone, likely in a dilational jog in a regional dextral strike-slip system. The oldest rocks are probably mafic sills, which heated the area facilitating emplacement of intermediate magmas. Cross-cutting relationships show that both mafic and intermediate magmas were supplied throughout the history of pluton emplacement. The modal composition, mineral chemistry, and bulk chemistry of gabbro, diorite, tonalite, granodiorite, and granite have been studied in the main plutonic phases, dykes, and sills, and mafic microgranular enclaves. As with the type appinites in the Scottish Caledonides, the pluton shows evidence of high water content: the dominance of hornblende, locally within pegmatitic texture; vesicles and irregular felsic patches in enclaves; and late aplite dykes. Analyzed mafic microgranular enclaves are geochemically similar to larger diorite bodies in the pluton. Tonalite-granodiorite is distinct from the diorite in trace-element geochemistry and radiogenic isotopes. Elsewhere to the east, similar rocks of the same age form vertically sheeted complexes in major shear zones; hornblende chemistry shows that they were emplaced at a deeper upper crustal level. This implies that little of the observed geochemical variability in the Jeffers Brook pluton was developed within the pluton. The general requirements to form appinites are proposed to be small magma volumes of subduction-related magmas that reach the upper crust because of continual heating by mafic magmas moving through strike-slip fault pathways and trapping of aqueous fluids rather than venting through volcanic activity.

  3. Lista comentada de las plantas vasculares del enclave seco interandino de la tatacoa (huila, colombia)

    OpenAIRE

    FIGUEROA-C., YISELA; GALEANO, GLORIA

    2012-01-01

    Se presenta el inventario florístico del enclave seco interandino de La Tatacoa (vallede la parte alta del río Magdalena, Huila, Colombia). Se encontraron 223 especies,distribuidas en 170 géneros y 60 familias. A nivel florístico, la familia Leguminosaees la más diversificada con 36 especies y 28 géneros, seguida por Poaceae (20/15),Euphorbiaceae (13/6), Asteraceae (10/10) y Cactaceae (8/7). El hábito de crecimientopredominante en términos de riqueza de especies fue el de las hierbas, seguido...

  4. Cerro Baúl: un enclave wari en interacción con Tiwanaku

    OpenAIRE

    Williams, Patrick Ryan; Isla, Johny A.; Nash, Donna J.

    2012-01-01

    Cerro Baul: A Wari Enclave Interacting with TiwanakuWari expansion to the extreme south of Peru is a phenomenon whose study began 20 years ago, with the discovery of a great arquitectonic complex at Cerro Baul. The excavations undertaken in the last 3 years have revealed that Cerro Baul was more than a military fortress; it was the most important political and religious center that Wari established in the only region where there is direct evidence of interaction with Tiwanaku, the altiplano s...

  5. Ciénaga (Magdalena, una región administrativa o municipio de enclave

    Directory of Open Access Journals (Sweden)

    Luis Humberto Hernández

    2006-01-01

    Full Text Available El análisis sobre las regiones de enclave, el caso del municipio de Ciénaga, en el Magdalena, nos permitió concluir que su proceso de modernización estuvo determinado por la presencia de la empresa multinacional bananera United Fruit Company. La multinacional bananera fue la que introdujo en la región el trabajo asalariado moderno, dislocando las formas serviles y premodernas existentes. Al atraer la mano de obra servil regional, que utilizaban las haciendas ganaderas, y convertirla en mano de obra asalariada, fundamentó sus procesos socioeconómicos y político administrativo modernos.

  6. The Urban Enclave, a Spatio–Temporal Logic of the Urbanized Periphery: Effects on Residential Segregation and Urban Fragmentation

    Directory of Open Access Journals (Sweden)

    Guénola Capron

    2016-07-01

    Full Text Available The production of the metropolitan peripheries in Latin America has been characterized by the development of urban, residential and commercial enclaves. These enclaves encompass both large urban housing projects of social interest and subdivisions and gated communities for high–income populations. Both peripheries respond to very different social reasons but have a common spatial logic: the enclave, which deepens the isolation and social distance with its surroundings, generating segregation and fragmentation. We seek to rescue the social and spatial processes of ‘enclosing’ or ‘insularity’ in two cases: a gated community in the northeast — Zona Esmeralda— and a social housing urban complex in the east —San Buenaventura—, both bordering the metropolitan area of the Mexico Valley.

  7. Another Mexican birthweight paradox? The role of residential enclaves and neighborhood poverty in the birthweight of Mexican-origin infants.

    Science.gov (United States)

    Osypuk, Theresa L; Bates, Lisa M; Acevedo-Garcia, Dolores

    2010-02-01

    Examining whether contextual factors influence the birth outcomes of Mexican-origin infants in the US may contribute to assessing rival explanations for the so-called Mexican health paradox. We examined whether birthweight among infants born to Mexican-origin women in the US was associated with Mexican residential enclaves and exposure to neighborhood poverty, and whether these associations were modified by nativity (i.e. mother's place of birth). We calculated metropolitan indices of neighborhood exposure to Mexican-origin population and poverty for the Mexican-origin population, and merged with individual-level, year 2000 natality data (n=490,332). We distinguished between neighborhood exposure to US-born Mexican-origin population (i.e. ethnic enclaves) and neighborhood exposure to foreign-born (i.e. Mexico-born) Mexican-origin population (i.e. immigrant enclaves). We used 2-level hierarchical linear regression models adjusting for individual, metropolitan, and regional covariates and stratified by nativity. We found that living in metropolitan areas with high residential segregation of US-born Mexican-origin residents (i.e. high prevalence of ethnic enclaves) was associated with lower birthweight for infants of US-born Mexican-origin mothers before and after covariate adjustment. When simultaneously adjusting for exposure to ethnic and immigrant enclaves, the latter became positively associated with birthweight and the negative effect of the former increased, among US-born mothers. We found no contextual birthweight associations for mothers born in Mexico in adjusted models. Our findings highlight a differential effect of context by nativity, and the potential health effects of ethnic enclaves, which are possibly a marker of downward assimilation, among US-born Mexican-origin women. Copyright 2009 Elsevier Ltd. All rights reserved.

  8. Triaxial Compression Testing of Multicomponent Geomaterials from Quartz-Poor (Syenitic Systems

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    Krmíček Lukáš

    2017-12-01

    Full Text Available This paper focuses on mafic microgranular enclaves enclosed in quartz-poor igneous rocks and their effect on strength properties of the rock massif. The study examines host rock–enclave multicomponent geomaterials from enclave-bearing syenitic rocks from the Třebíč Massif exposed in the Královec quarry near Jaroměřice nad Rokytnou in the Czech Republic. A series of laboratory tests were performed to describe strength properties of individual constituents of the multicomponent geomaterials. We mainly focused on triaxial compression tests, however, rebound hardness, uniaxial compressive strength and indirect tensile strength were determined as well. The obtained results indicate that enclaves and even the contact zones between the enclaves and host rocks do not have any negative influence on the rock strength. In contrast, enclaves represent “stress concentrators” within such multicomponent systems. Strength properties of various multicomponent geomaterials are practically an unexplored topic in the field of rocks mechanics and future studies are needed to establish a robust database describing the behaviour of such geocomposites.

  9. At the southern edge of the EU: Identity challenges affecting the Spanish enclaves of Ceuta and Melilla

    DEFF Research Database (Denmark)

    Castan Pinos, Jaume

    2009-01-01

    Europe. Thus, the anomalous geographical location of both Spanish cities exposes them to border and identity challenges as well as to a complex situation of interdependent concentric circles which involves the enclaves (first circle), Spain, Morocco (second circle) and the EU (third circle). The aim...... of fortress Europe. Thus, the anomalous geographical location of both Spanish cities exposes them to border and identity challenges as well as to a complex situation of interdependent concentric circles which involves the enclaves (first circle), Spain, Morocco (second circle) and the EU (third circle...

  10. Anthropological Critique and Framing of Suburban Enclaves: Case of Neighbourhood X

    Directory of Open Access Journals (Sweden)

    Butko Matej

    2016-06-01

    Full Text Available The main point of this article is conceptualization of newcomers within specific suburb in perimeter of Bratislava. The analysis with fruitful and extensive base of evidence provides a connection between the western suburban community theories and local actual and discursive strategies in various topics. The content of this article consists of analysis of bonding, residential and motivational strategies of newcomers, and a wide conceptualization of them, including a class concept and a bounding character of socialization. Additional analytical and evidential asset of this article is the perceptiveness that provides us the ‘other-than-actual’ evaluative perspective. This perception is provided by other inhabitants outside of the researched Neighbourhood X. This evidence, which is connected to the theory of leisure class consumption, is therefore the perceptive side of the core definition of enclaves in residentially excluded neighbourhood. This article offers conclusions of a specific field experience and broadens not only the existing suburban community theories, but also the works that try to conceptualise significant traits of suburban enclaves.

  11. Enacting trust: contract, law and informal economic relationships in a Spanish border enclave in Morocco

    Directory of Open Access Journals (Sweden)

    Brian Campbell

    2012-01-01

    Full Text Available Small and removed from the Spanish mainland, the Enclave of Ceuta has always depended on flows of goods and labour out of the Moroccan hinterland, with individuals from different ethnic and religious groups forming informal, flexible and personal economic bonds based on mutual ‘confianza’ (trust. Since its entry into the European Union in 1986,the Spanish government has erected a border-wall around the enclave, and introduced new migration policies branding many informal workers within its borders as a threat to Spanish society. Based on my preliminary months of research, this paper compares the Ceutancontext with other research recently conducted on the topics of migration and borders in the Mediterranean region. It brings into focus key theoretical issues and assumptions that constantly emerge in such literature, particularly regarding the role of ‘a-cultural’ personal ties between migrants and locals in undermining State categories and ideology. This paper observes how the Ceutan case encourages us to expand our focuses and consequently problematise our understanding of crucial concepts such as ‘trust’ and ‘integration’.

  12. Understanding the monotonous life of open vent mafic volcanoes

    Science.gov (United States)

    Costa Rodriguez, F.; Ruth, D. C. S.; Bornas, M.; Rivera, D. J. V. I.

    2016-12-01

    Mafic open vent volcanoes display prominent degassing plumes during quiescence but also erupt frequently, every few months or years. Their small and mildly explosive eruptions (volatile contents indicate that the magma reservoir system extends at least to 5 km depth. Mg/Fe pyroxene zoning and diffusion modeling suggests that mafic magma intrusion in a shallow, crystal-rich and more evolved reservoir has occurred repeatedly. The time scale for this process is the same for all 9 events, starting about 2 years prior and continuing up to eruption. We estimate the relative proportions of injecting to resident magma that vary from about 0.2 to 0.7, probably reflecting the local crystal-melt interaction during intrusion. The near constant magma composition is probably the result of buffering of new incoming magma by a crystal-rich upper reservoir, and erupted magmas are physical mixtures. However, we do not find evidence of large-scale crystal recycling from one eruption to another, implying the resetting of the system after each event. The recurrent eruptions and intrusions could be driven by the near continuous degassing of the volcano that induces a mass imbalance which leads to magma movement from depth to the shallow system [e.g., 1]. [1] Girona et al. (2016). Science Reports doi:10.1038/srep18212

  13. 75 FR 69717 - In the Matter of: Edentify, Inc., Embryo Development Corp., Enclaves Group, Inc., Energytec, Inc...

    Science.gov (United States)

    2010-11-15

    ... SECURITIES AND EXCHANGE COMMISSION [File No. 500-1] In the Matter of: Edentify, Inc., Embryo Development Corp., Enclaves Group, Inc., Energytec, Inc., Enesco Group, Inc., Entertainment Is Us, Inc... Commission that there is a lack of current and accurate information concerning the securities of Embryo...

  14. Trabajo y relaciones laborales en los enclaves minero-metalúrgicos de la Amazonia

    Directory of Open Access Journals (Sweden)

    Josep Pont Vidal

    2008-04-01

    Full Text Available Abstract:  Labour and labour relations in the enclaves of metallurgical mining in the AmazonThis article is based upon an empirical study of  life and labour conditions in the metallurgical  mining enclaves of the eastern Amazon region.  From the perspective of civil society (associations  of workers, labour conditions are analysed according to interviews with workers and their  family members given outside the work sphere.  Using the method based on ‘grounded theory’, and specifically on the qualitative analysis of  theorization, a scheme of two levels has been  made: the ‘situational activity’ and the ‘subjectivization of the activity’. The first level, the ‘situational activity’, is centred in the sphere of the  organizations of workers and their perceptions  and strategies for action. The second level, the  ‘subjective of the activity’, addresses the subjective interpretations adopted by workers and their  families. Resumen:Este escrito se basa en un estudio empírico de las  condiciones de vida y relaciones laborales en los  enclaves minero-metalúrgicos de la Amazonia  oriental. En él se analizan las condiciones laborales desde la perspectiva de la sociedad civil (asociaciones de trabajadores, recurriendo para ello a  entrevistas con trabajadores y sus familias fuera  del ambiente de trabajo. A partir del método basado en la teorización anclada, y específicamente  en el denominado análisis cualitativo de teorización, se ha confeccionado un esquema de dos  niveles: la ‘actividad situacional’, y la ‘subjetivización de la actividad’. El primer nivel -la ‘actividad situacional’- se centra en la esfera de las  organizaciones de trabajadores y sus ideas y estrategias de acción. El segundo nivel -la ‘subjetivización de la actividad’- trata las interpretaciones  subjetivas adoptadas por los trabajadores y sus  familias.

  15. Enclaves sanitarios: higiene, epidemias y salud en el Barrio chino de Lima, 1880-1910

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    Patricia Palma

    2018-01-01

    Full Text Available El Barrio chino de Lima, el más antiguo de América Latina, fue objeto de una serie de conflictos y estereotipos determinados por la raza y la salud pública durante el cambio de siglo. Una alianza entre médicos y autoridades políticas hizo de este espacio un lugar que atentaba contra la salud pública y el proyecto modernizador, aun cuando un importante grupo de limeños -especialmente las clases populares de la ciudad-, encontraron en los médicos chinos y sus tratamientos una alternativa médica viable y a un precio accesible. Reexaminando al Barrio chino como un enclave sanitario, este ensayo ofrece una mirada distinta a la relación entre autoridades, médicos inmigrantes y pacientes, a partir de fuentes como canciones, caricaturas y descripciones de viajeros.

  16. Mobilidad laboral geográfica en un antiguo enclave minero

    Directory of Open Access Journals (Sweden)

    Camilo Contreras Delgado

    1999-01-01

    Full Text Available Este artículo examina los fa c t o res internos y externos a una localidad que son copartícipes en la estructuración y reestructuración de su mercado de trabajo local. A partir de la revisión de la historia social y económica del lugar, se destaca su tránsito de enclave minero a lugar de residencia de mineros y trabajadores de maquiladoras. En este caso, se presenta la constitución de los mercados de trabajo locales como un resultado del encuentro de las condiciones del lugar de residencia de los trabajadores y el lugar donde se encuentra el centro de trabajo. De aquí que la movilidad laboral geográfica aparezca como una de las tácticas de los sujetos ante una situación de desempleo.

  17. Geomechanical analyses to investigate wellbore/mine interactions in the Potash Enclave of Southeastern New Mexico.

    Energy Technology Data Exchange (ETDEWEB)

    Ehgartner, Brian L.; Bean, James E. (Sandia Staffing Alliance, LLC, Albuquerque, NM); Arguello, Jose Guadalupe, Jr.; Stone, Charles Michael

    2010-04-01

    Geomechanical analyses have been performed to investigate potential mine interactions with wellbores that could occur in the Potash Enclave of Southeastern New Mexico. Two basic models were used in the study; (1) a global model that simulates the mechanics associated with mining and subsidence and (2) a wellbore model that examines the resulting interaction impacts on the wellbore casing. The first model is a 2D approximation of a potash mine using a plane strain idealization for mine depths of 304.8 m (1000 ft) and 609.6 m (2000 ft). A 3D wellbore model then considers the impact of bedding plane slippage across single and double cased wells cemented through the Salado formation. The wellbore model establishes allowable slippage to prevent casing yield.

  18. Crafting a Democratic Enclave on the Cyberspace: Case Studies of Malaysia, Indonesia, and Singapore

    Directory of Open Access Journals (Sweden)

    Yangyue Liu

    2011-01-01

    Full Text Available As an antithesis of “authoritarian enclave” which has been well-established in the comparative politics literature, “democratic enclave” points to the institution of a state or the unambiguous regulatory space in society “where the authoritarian regime’s writ is substantively limited and is replaced by an adherence to recognizably democratic norms and procedures” (Gilley 2010. In this sense, the Internet space, embodied by information and communication technologies, has great potential to play such a role, since its “inherited” properties of decentralization and anonymity would inevitably breach the authoritarian rules. However, a closer look at three Southeast Asian states, Malaysia, Singapore and the “New Order” Indonesia whose regimes were characterized by authoritarianism when Internet was initially developed, reveals different trajectories. In the “New Order” Indonesia and Malaysia, the governments consciously left the Internet space uncontrolled; the online media developed independently, vibrantly, and professionally, especially in the Malaysian case; and there were strong connections between online and offline contentious politics. These elements made the Internet space in Indonesia and Malaysia a successful case of democratic enclave. Based on these criteria, however, the Internet space in Singapore has not achieved similar status. This paper analyses the different outcomes of enclave creation on the cyberspace among these countries. It argues that elite conflict and the strength of civil society are the two major factors that shape the differences. In this sense, the political contexts are of great importance for the understanding of Internet’s political impacts.

  19. Drilling the Bushveld Complex- the world's largest layered mafic intrusion

    Science.gov (United States)

    Ashwal, L. D.; Webb, S. J.; Trumbull, R. B.

    2013-12-01

    The fact that surprising new discoveries can be made in layered mafic intrusions (e.g., subtle 100-150 m cyclicity in apparently homogeneous cumulates over 1000s of m) means that we are still in the first-order characterization phase of understanding these objects. Accordingly, we have secured funding from ICDP for a planning workshop to be held in Johannesburg in early 2014, aimed at scientific drilling of the Bushveld Complex, the world's largest layered mafic intrusion. Science objectives include, but are not limited to: 1. Magma chamber processes & melt evolution. How many melts/magmas/mushes were involved, what were their compositions and how did they interact? What, if anything, is missing from the Complex, and where did it go? Did Bushveld magmatism have an effect upon Earth's atmosphere at 2 Ga? 2. Crust-mantle interactions & origin of Bushveld granitoids. Are Bushveld granites & rhyolites crustal melts, differentiates from the mafic magmas or products of immiscibility? How can the evolved isotopic signatures in the mafic rocks (e.g., epsilon Nd to -8) be understood? 3. Origin of ore deposits. What were the relative roles of gravity settling, magma mixing, immiscibility and hydrothermal fluid transport in producing the PGE, Cr and V deposits? We have identified 3 potential drilling targets representing a total of ~12 km of drill core. Exact locations of drill sites are to be discussed at the workshop. Target A- East-Central Bushveld Complex. We propose 3 overlapping 3 km boreholes that will provide the first roof-to-floor continuous coverage of the Rustenburg Layered Suite. These boreholes will represent a curated, internationally available reference collection of Bushveld material for present and future research. Target B- Southeastern Bushveld Complex. We propose a single borehole of ~2 km depth, collared in Rooiberg felsite, and positioned to intersect the Roof Zone, Upper Zone, Main Zone and floor of the Complex. Amongst other things, this site will

  20. Petrological constraints on the recycling of mafic crystal mushes, magma ascent and intrusion of braided sills in the Torres del Paine mafic complex (Patagonia)

    Science.gov (United States)

    Leuthold, Julien; Müntener, Othmar; Baumgartner, Lukas; Putlitz, Benita

    2014-05-01

    Cumulate and crystal mush disruption and reactivation are difficult to recognise in coarse grained shallow plutonic rocks. Mafic minerals included in hornblende and zoned plagioclase provide snapshots of early crystallization and cumulate formation, but are difficult to interpret in terms of the dynamics of magma ascent and possible links between silicic and mafic rock emplacement. We will present the field relations, the microtextures and the mineral chemistry of the Miocene mafic sill complex of the Torres del Paine intrusive complex (Patagonia, Chile) and its sub-vertical feeder-zone. The mafic sill complex was built up by a succession of braided sills of shoshonitic and high-K calc-alkaline porphyritic hornblende-gabbro and fine grained monzodioritic sills. The mafic units were over-accreted over 41±11 ka, underplating the overlying granite. Local diapiric structures and felsic magma accumulation between sills indicate limited separation of intercumulus liquid from the mafic sills. Anhedral hornblende cores, with olivine + clinopyroxene ± plagioclase ± apatite inclusions, crystallized at temperatures >900°C and pressures of ~300 to ~500 MPa. The corresponding rims and monzodiorite matrix crystallized at 950°C) from the middle crust reservoir to the emplacement level. We show that hornblende-plagioclase thermobarometry is a useful monitor for the determination of segregation conditions of granitic magmas from gabbroic crystal mushes, and for monitoring the evolution of shallow crustal magmatic crystallization, decompression and cooling.

  1. Thermal diffusivity of felsic to mafic granulites at elevated temperatures

    Science.gov (United States)

    Ray, Labani; Förster, H.-J.; Schilling, F. R.; Förster, A.

    2006-11-01

    The thermal diffusivity of felsic and intermediate granulites (charnockites, enderbites), mafic granulites, and amphibolite-facies gneisses has been measured up to temperatures of 550 °C using a transient technique. The rock samples are from the Archean and Pan-African terranes of the Southern Indian Granulite Province. Thermal diffusivity at room temperature ( DRT) for different rock types ranges between 1.2 and 2.2 mm 2 s - 1 . For most of the rocks, the effect of radiative heat transfer is observed at temperatures above 450 °C. However, for few enderbites and mafic granulites, radiative heat transfer is negligible up to 550 °C. In the temperature range of conductive heat transfer, i.e., between 20 ° and 450 °C, thermal diffusivity decreases between 35% and 45% with increasing temperature. The temperature dependence of the thermal diffusivity is directly correlated with the thermal diffusivity at room temperature, i.e., the higher the thermal diffusivity at room temperature, DRT, the greater is its temperature dependence. In this temperature range i.e., between 20 and 450 °C, thermal diffusivity can be expressed as D = 0.7 mm 2 s -1 + 144 K ( DRT - 0.7 mm 2 s -1 ) / ( T - 150 K), where T is the absolute temperature in Kelvin. At higher temperatures, an additional radiative contribution is observed according to CT3, where C varies from 10 - 9 to 10 - 10 depending on intrinsic rock properties (opacity, absorption behavior, grain size, grain boundary, etc). An equation is presented that describes the temperature and pressure dependence thermal diffusivity of rocks based only on the room-temperature thermal diffusivity. Room-temperature thermal diffusivity and its temperature dependence are mainly dependent on the major mineralogy of the rock. Because granulites are important components of the middle and lower continental crust, the results of this study provide important constraints in quantifying more accurately the thermal state of the deeper continental

  2. Crustal contamination versus an enriched mantle source for intracontinental mafic rocks: Insights from early Paleozoic mafic rocks of the South China Block

    Science.gov (United States)

    Xu, Wenjing; Xu, Xisheng; Zeng, Gang

    2017-08-01

    Several recent studies have documented that the silicic rocks (SiO2 > 65 wt.%) comprising Silicic Large Igneous Provinces are derived from partial melting of the crust facilitated by underplating/intraplating of "hidden" large igneous province-scale basaltic magmas. The early Paleozoic intracontinental magmatic rocks in the South China Block (SCB) are dominantly granitoids, which cover a combined area of 22,000 km2. In contrast, exposures of mafic rocks total only 45 km2. These mafic rocks have extremely heterogeneous isotopic signatures that range from depleted to enriched (whole rock initial 87Sr/86Sr = 0.7041-0.7102; εNd(t) = - 8.4 to + 1.8; weighted mean zircon εHf(t) = - 7.4 to + 5.2), show low Ce/Pb and Nb/U ratios (0.59-13.1 and 3.5-20.9, respectively), and variable Th/La ratios (0.11-0.51). The high-MgO mafic rocks (MgO > 10 wt.%) tend to have lower εNd(t) values (- 4) and Sm/Nd ratios (> 0.255). The differences in geochemistry between the high-MgO and low-MgO mafic rocks indicate greater modification of the compositions of high-MgO mafic magmas by crustal material. In addition, generally good negative correlations between εNd(t) and initial 87Sr/86Sr ratios, MgO, and K2O, along with the presence of inherited zircons in some plutons, indicate that the geochemical and isotopic compositions of the mafic rocks reflect significant crustal contamination, rather than an enriched mantle source. The results show that high-MgO mafic rocks with fertile isotopic compositions may be indicative of crustal contamination in addition to an enriched mantle source, and it is more likely that the lithospheric mantle beneath the SCB during the early Paleozoic was moderately depleted than enriched by ancient subduction processes.

  3. How Does the Context of Reception Matter? The Role of Residential Enclaves in Maternal Smoking During Pregnancy Among Mexican-Origin Mothers.

    Science.gov (United States)

    Noah, Aggie J; Landale, Nancy S; Sparks, Corey S

    2015-08-01

    This study investigated whether and how different patterns of group exposure within residential contexts (i.e., living in a Mexican immigrant enclave, a Mexican ethnic enclave, a pan-Hispanic enclave, or a non-Hispanic white neighborhood) are associated with smoking during pregnancy among Mexican-origin mothers. Using a hierarchical linear modeling approach, we found that Mexican-origin mothers' residential contexts are important for understanding their smoking during pregnancy. Residence in an ethnic enclave is associated with decreased odds of smoking during pregnancy, while residence in a non-Hispanic white neighborhood is associated with increased odds of smoking during pregnancy, above and beyond the mothers' individual characteristics. The magnitude of the associations between residence in an ethnic enclave and smoking during pregnancy is similar across the different types of ethnic enclaves examined. The important roles of inter- and intra-group exposures suggests that in order to help Mexican-origin women, policy makers should more carefully design place-based programs and interventions that target geographic areas and the specific types of residential contexts in which women are at greater risk.

  4. Mafic Materials in Scott Crater? A Test for Lunar Reconnaissance Orbiter

    Science.gov (United States)

    Cooper, Bonnie L.

    2007-01-01

    Clementine 750 nm and multispectral ratio data, along with Lunar Orbiter and radar data, were used to study the crater Scott in the lunar south polar region. The multispectral data provide evidence for mafic materials, impact melts, anorthositic materials, and a small pyroclastic deposit. High-resolution radar data and Lunar Orbiter photography for this area show differences in color and surface texture that correspond with the locations of the hypothesized mafic and anorthositic areas on the crater floor. This region provides a test case for the upcoming Lunar Reconnaissance Orbiter. Verification of the existence of a mafic deposit at this location is relevant to future lunar resource utilization planning.

  5. Possible Mafic Patches in Scott Crater Highlight the Need for Resource Exploration on the Lunar South Polar Region

    Science.gov (United States)

    Cooper, Bonnie L.

    2007-01-01

    Possible areas of mafic material on the rim and floor of Scott crater (82.1 deg S, 48.5 deg E) are suggested by analysis of shadow-masked Clementine false-color-ratio images. Mafic materials common in mare and pyroclastic materials can produce more oxygen than can highlands materials, and mafic materials close to the south pole may be important for propellant production for a future lunar mission. If the dark patches are confirmed as mafic materials, this finding would suggest that other mafic patches may exist, even closer to the poles, which were originally mapped as purely anorthositic.

  6. LISTA COMENTADA DE LAS PLANTAS VASCULARES DEL ENCLAVE SECO INTERANDINO DE LA TATACOA (HUILA, COLOMBIA

    Directory of Open Access Journals (Sweden)

    FIGUEROA-C. YISELA

    2007-12-01

    Full Text Available Se presenta el inventario florístico del enclave seco interandino de La Tatacoa (vallede la parte alta del río Magdalena, Huila, Colombia. Se encontraron 223 especies,distribuidas en 170 géneros y 60 familias. A nivel florístico, la familia Leguminosaees la más diversificada con 36 especies y 28 géneros, seguida por Poaceae (20/15,Euphorbiaceae (13/6, Asteraceae (10/10 y Cactaceae (8/7. El hábito de crecimientopredominante en términos de riqueza de especies fue el de las hierbas, seguido porlos hábitos leñosos (árboles, arbustos y sufrútices, y el mayor número de especiesse encontró en las zonas de áreas abiertas y en las riberas de quebradas. Se registrancuatro hallazgos corológicos interesantes, incluyendo el primer registro de Sennauniflora para Colombia.

  7. From authoritarian enclave to deliberative space: governance logics in post-disaster reconstruction.

    Science.gov (United States)

    Curato, Nicole

    2018-02-27

    One would be hard-pressed nowadays to find any practitioners and scholars in the field of post-disaster reconstruction who would argue against the virtues of community participation. In practice, however, the legacy of community participation has been mixed. This paper pursues this line of inquiry by examining the manifestations of participation in three communities affected by Typhoon Haiyan that struck the Philippines on 8 November 2013. The findings suggest that different governance logics emerge in each of the three case studies: authoritarian; communitarian; and deliberative. These logics promote particular understandings of who should participate in the reconstruction process and the appropriate scope of action for citizens to express discontent, provide feedback, and perform democratic agency. The paper contends that design interventions in participatory procedures, as well as contingencies in wider social contexts, shape the character and legacies of community participation. It concludes by comparing the legacies of these three 'governance enclaves' and imagining possibilities for participatory politics in post-disaster settings. © 2018 The Author(s). Disasters © Overseas Development Institute, 2018.

  8. The drugs industry and peasant self-defence in a Peruvian cocaine enclave.

    Science.gov (United States)

    van Dun, Mirella

    2012-11-01

    This article gives a detailed account of the cocaine industry and the related violence in the Peruvian Upper Huallaga. It is argued that in this cocaine producing region violence increased during state-led forced eradication operations of the coca plants. Most of the violent incidents were closely related to the diminishing cocaine industry, but they were also related to the actions of the state security forces. Instead of receiving support from the state's security apparatus, the population mobilized its own forces to fight the violence. As will be argued, the causes of violence in this cocaine enclave are part of a dynamic interaction amongst many factors - an interaction that is influenced by the local context, a partial state vacuum, and the social utility and the economic advantages of violence. One needs to be aware that motivations of those who engage in the violent behaviour can change over time, as underlying power structures are influenced by changes in local conditions. The study covers an in-depth account of events taking place in the Upper Huallaga during the years 2003-2007. The research material was collected by several ethnographical fieldwork methods. Copyright © 2012 Elsevier B.V. All rights reserved.

  9. Mafic inclusions in Yosemite granites and Lassen Pk lavas: records of complex crust-mantle interactions

    Energy Technology Data Exchange (ETDEWEB)

    Reid, J.B. Jr.; Flinn, J.E.

    1985-01-01

    This study compares three small-scale magmatic systems dominated by mafic/felsic interaction that appear to be analogs to the evolution of their larger host systems: mafic inclusions from modern Lassen Pk lavas along with inclusions and related synplutonic dike materials from granitoids in the Tuolumne Intrusive Series. Each system represents quickly chilled mafic melt previously contaminated by digestion of rewarmed, super-solidus felsic hosts. Contaminants occur in part as megacrysts of reworked oligoclase with lesser hb and biot. Within each group MgO-variation diagrams for Fe, Ca, Ti, Si are strikingly linear (r>.96); alkalis are decidedly less regular, and many hybrid rocks show a curious, pronounced Na enrichment. Field data, petrography, and best fit modeling suggests this may result from flow concentration of oligoclase xenocrysts within contaminated synplutonic dikes, and is preserved in the inclusions when dike cores chill as pillows in their felsic host. Dissolution of mafic inclusions erases these anomalies and creates a more regular series of two-component mafic-felsic mixtures in the large host system. The inclusions and dikes thus appear to record a variety of late-stage mafic-felsic interactive processes that earlier and on a larger scale created much of the compositional variety of their intermediate host rocks.

  10. Are immigrant enclaves healthy places to live? The Multi-ethnic Study of Atherosclerosis.

    Science.gov (United States)

    Osypuk, Theresa L; Diez Roux, Ana V; Hadley, Craig; Kandula, Namratha R

    2009-07-01

    The growing size and changing composition of the foreign-born population in the USA highlights the importance of examining the health consequences of living in neighborhoods with higher proportions of immigrants. Using data from the Multi-ethnic Study of Atherosclerosis in four US cities, we examined whether neighborhood immigrant composition was associated with health behaviors (diet, physical activity) among Hispanic and Chinese Americans (n=1902). Secondarily we tested whether neighborhoods with high proportions of immigrants exhibited better or worse neighborhood quality, and whether these dimensions of neighborhood quality were associated with healthy behaviors. Neighborhood immigrant composition was defined based on the Census 2000 tract percent of foreign-born from Latin-America, and separately, percent foreign-born from China. After adjustment for age, gender, income, education, neighborhood poverty, and acculturation, living in a tract with a higher proportion of immigrants was associated with lower consumption of high-fat foods among Hispanics and Chinese, but with being less physically active among Hispanics. Residents in neighborhoods with higher proportions of immigrants reported better healthy food availability, but also worse walkability, fewer recreational exercise resources, worse safety, lower social cohesion, and lower neighborhood-based civic engagement. Associations of neighborhood immigrant composition with diet persisted after adjustment for reported neighborhood characteristics, and associations with physical activity were attenuated. Respondent-reported neighborhood healthy food availability, walkability, availability of exercise facilities and civic participation remained associated with behaviors after adjusting for immigrant composition and other covariates. Results show that living in an immigrant enclave is not monolithically beneficial and may have different associations with different health behaviors.

  11. Intraplate mafic magmatism: New insights from Africa and N. America

    Science.gov (United States)

    Ebinger, C. J.; van der Lee, S.; Tepp, G.; Pierre, S.

    2017-12-01

    Plate tectonic concepts consider that continental interiors are stable, with magmatism and strain localized to plate boundaries. We re-evaluate the role of pre-existing and evolving lithospheric heterogeneities in light of perspectives afforded by surface to mantle results from active and ancient rift zones in Africa and N. America. Our process-oriented approach addresses the localization of strain and magmatism and stability of continental plate interiors. In both Africa and N. America, geophysical imaging and xenolith studies reveal that thick, buoyant, and chemically distinct Archaean cratons with deep roots may deflect mantle flow, and localize magmatism and strain over many tectonic cycles. Studies of the Colorado Plateau and East African rift reveal widespread mantle metasomatism, and high levels of magma degassing along faults and at active volcanoes. The volcanoes and magmatic systems show a strong dependence on pre-existing heterogeneities in plate structure. Syntheses of the EarthScope program ishow that lateral density contrasts and migration of volatiles that accumulated during subduction can refertilize mantle lithosphere, and enable volatile-rich magmatism beneath relatively thick continental lithosphere. For example, the passive margin of eastern N. America shows uplift and magmatism long after the onset of seafloor spreading, demonstrating the dynamic nature of coupling between the lithosphere, asthenosphere, and deeper mantle. As demonstrated by the East African Rift, the Mid-Continent Rift, and other active and ancient rift zones, the interiors of continents, including thick, cold Archaean cratons are not immune to mafic magmatism and tectonism. Recent studies in N. America and Africa reveal ca. 1000 km-wide zones of dynamic uplift, low upper mantle velocities, and broadly distributed strain. The distribution of magmatism and volatile release, in combination with geophysical signals, indicates a potentially convective origin for widespread

  12. Les savanes d'Afrique centrale entre enclavement et intégration aux marchés

    OpenAIRE

    Magrin , Géraud; Jamin , Jean-Yves; Faure , Guy; Duteurtre , Guillaume

    2003-01-01

    International audience; Les savanes d'Afrique centrale qui s'étendent à travers le nord du Cameroun, le sud du Tchad et la République centrafricaine présentent une certaine homogénéité. Milieux de transition entre Sahel et Afrique forestière, ce sont des espaces enclavés, encore peu urbanisés, au peuplement contrasté, où la culture cotonnière marque fortement les systèmes agraires. Des changements rapides sont néanmoins en cours. La croissance démographique encourage l'intensification des cul...

  13. Geochemistry of PGE in mafic rocks of east Khasi Hills, Shillong ...

    Indian Academy of Sciences (India)

    study area. The studied mafic rocks of east Khasi Hills cover an area of about 4 km2 and represent .... In contrast to the global scenario, attempts for ..... chemical. Sp. no. structural mo de. Mineral comp o sition classification. M g#*. (wt%). (wt%).

  14. 50 Myr of pulsed mafic magmatism in the High Arctic Large Igneous Province

    Science.gov (United States)

    Pearson, D. G.; Dockman, D. M.; Heaman, L. M.; Gibson, S. A.; Sarkar, C.

    2017-12-01

    Extensive and voluminous Cretaceous mafic magmatism in the Sverdrup Basin of Arctic Canada forms the circum-Arctic High Arctic Large Igneous Province (HALIP). The small number of published high-precision ages for this LIP indicate its eruption over a considerable timespan raising concerns over whether the HALIP can be strictly defined as a single LIP and questioning the role of a single or multiple plumes in its genesis. Here we present an integrated geochemical and geochronological study to better constrain the timing and cause of mafic magma genesis in the Canadian HALIP. Six new U-Pb and four 40Ar/39Ar ages of mafic lavas and intrusive sheets range from 121 Ma to 78 Ma. The U-Pb ages are the first analyzed from the mafic intrusions of Axel Heiberg and Ellesmere Islands. The new geochronology, combined with other published high-precision ages, reveal a > 50 Myr duration of mafic magmatism in the HALIP defined by three main pulses. Tholeiites dominate the initial 25 Myr of magmatism, transitioning to coeval emplacement of alkali and tholeiitic basalts. Whole-rock Sr-Nd isotope ratios indicate that both magma types are derived from a similar source dominated by convecting mantle. Rare-earth-element inversion models reveal that the alkalic and tholeiitic magmas were generated beneath a bimodal lithospheric `lid' thickness of 65 ± 5 and 45 ± 4 km, respectively. We suggest that the early 128 - 122 Ma tholeiitic event is primarily plume-generated and correlates across the circum-Arctic with the other HALIP tholeiites. Younger HALIP magmatism, with coeval alkalic and tholeiitic magmas erupting over 25 Myr, may be explained by alternating modes of edge-driven mantle convection as the primary control on magma genesis. A distal plume may have intensified magma production by edge-driven convection.

  15. Source characteristics and tectonic setting of mafic-ultramafic intrusions in North Xinjiang, NW China: Insights from the petrology and geochemistry of the Lubei mafic-ultramafic intrusion

    Science.gov (United States)

    Chen, Bao-Yun; Yu, Jin-Jie; Liu, Shuai-Jie

    2018-05-01

    The newly discovered Lubei sulfide-bearing mafic-ultramafic intrusion forms the western extension of the Huangshan-Jin'erquan mafic-ultramafic intrusion belt in East Tianshan, NW China. The Lubei intrusion comprises hornblende peridotite, lherzolite, and harzburgite in its southern portion, gabbro in its middle portion, and hornblende gabbro in its northern portion. Intrusive relationships indicate that three magma pulses were involved in the formation of the intrusion, and that they were likely evolved from a common primitive magma. Estimated compositions of the Lubei primitive magma are similar to those of island arc calc-alkaline basalt except for the low Na2O and CaO contents of the Lubei primitive magma. This paper reports on the mineral compositions, whole-rock major and trace element contents, and Rb-Sr and Sm-Nd isotopic compositions of the Lubei intrusion, and a zircon LA-MC-ICP-MS U-Pb age for hornblende gabbro. The Lubei intrusion is characterized by enrichment in large-ion lithophile elements, depletion in high-field-strength elements, and marked negative Nb and Ta anomalies, with enrichment in chondrite-normalized light rare earth elements. It exhibits low (87Sr/86Sr)i ratios of 0.70333-0.70636 and low (143Nd/144Nd)i ratios of 0.51214-0.51260, with positive εNd values of +4.01 to +6.33. LA-ICP-MS U-Pb zircon ages yielded a weighted-mean age of 287.9 ± 1.6 Ma for the Lubei intrusion. Contemporaneous mafic-ultramafic intrusions in different tectonic domains in North Xinjiang show similar geological and geochemical signatures to the Lubei intrusion, suggesting a source region of metasomatized mantle previously modified by hydrous fluids from the slab subducted beneath the North Xinjiang region in the early Permian. Metasomatism of the mantle was dominated by hydrous fluids and was related to subduction of the Paleo-Asian oceanic lithosphere during the Paleozoic. Sr-Nd-Pb isotopic compositions suggest that the mantle source was a mixture of depleted mid

  16. Partitioning of Cu between mafic minerals, Fe-Ti oxides and intermediate to felsic melts

    Science.gov (United States)

    Liu, Xingcheng; Xiong, Xiaolin; Audétat, Andreas; Li, Yuan

    2015-02-01

    This study used improved capsule technique i.e., Pt95Cu05 or Au95Cu05 alloy capsules as Cu sources to determine Cu partitioning between mafic minerals, Fe-Ti oxides and intermediate to felsic melts at 0.5-2.5 GPa, 950-1100 °C and various oxygen fugacities (fO2). In combination with the data from the mafic composition systems, the results demonstrate that Cu is generally highly incompatible in mafic minerals and moderately incompatible to compatible in Fe-Ti oxides. The general order of mineral/melt Cu partition coefficients (DCu) is garnet (0.01-0.06) ⩽ olivine (0.04-0.20) ≈ opx (0.04-0.24) ≈ amphibole (0.04-0.20) ⩽ cpx (0.04-0.45) ⩽ magnetite, titanomagnetite and Cr-spinel (0.18-1.83). The variations in DCu depend mainly on temperature, fO2 or mineral composition. In general, DCu for olivine (and perhaps opx) increases with decreasing temperature and increasing fO2. DCu increases for cpx with Na+ (pfu) in cpx, for magnetite and Cr-spinel with Fe3+ (pfu) in these phases and for titanomagnetite with Ti4+ (pfu) in this phase. The large number of DCu data (99 pairs) serves as a foundation for quantitatively understanding the behavior of Cu during magmatic processes. The generation of intermediate to felsic magmas via fractional crystallization or partial melting of mafic rocks (magmas) at deep levels of crust involves removal of or leaving assemblages of mafic minerals + Fe-Ti oxides ± sulfides. With our DCu data on mafic minerals and Fe-Ti oxides, DCubulk values around 0.2 were obtained for the sulfide-free assemblages. Cu will thus be concentrated efficiently in the derived melts during these two processes if sulfides are absent or negligible, explaining that high fO2 and sulfide-destabilization are favorable to formation of the porphyry Cu system.

  17. Paleomagnetic record of a geomagnetic field reversal from late miocene mafic intrusions, southern nevada.

    Science.gov (United States)

    Ratcliff, C D; Geissman, J W; Perry, F V; Crowe, B M; Zeitler, P K

    1994-10-21

    Late Miocene (about 8.65 million years ago) mafic intrusions and lava flows along with remagnetized host rocks from Paiute Ridge, southern Nevada, provide a high-quality paleomagnetic record of a geomagnetic field reversal. These rocks yield thermoremanent magnetizations with declinations of 227 degrees to 310 degrees and inclinations of -7 degrees to 49 degrees , defining a reasonably continuous virtual geomagnetic pole path over west-central Pacific longitudes. Conductive cooling estimates for the intrusions suggest that this field transition, and mafic magmatism, lasted only a few hundred years. Because this record comes principally from intrusive rocks, rather than sediments or lavas, it is important in demonstrating the longitudinal confinement of the geomagnetic field during a reversal.

  18. Aleutian tholeiitic and calc-alkaline magma series I: The mafic phenocrysts

    Science.gov (United States)

    Kay, S. Mahlburg; Kay, Robert W.

    1985-07-01

    Diagnostic mafic silicate assemblages in a continuous spectrum of Aleutian volcanic rocks provide evidence for contrasts in magmatic processes in the Aleutian arc crust. Tectonic segmentation of the arc exerts a primary control on the variable mixing, fractional crystallization and possible assimilation undergone by the magmas. End members of the continuum are termed calc-alkaline (CA) and tholeiitic (TH). CA volcanic rocks (e.g., Buldir and Moffett volcanoes) have low FeO/MgO ratios and contain compositionally diverse phenocryst populations, indicating magma mixing. Their Ni and Cr-rich magnesian olivine and clinopyroxene come from mantle-derived mafic olivine basalts that have mixed with more fractionated magmas at mid-to lower-crustal levels immediately preceding eruption. High-Al amphibole is associated with the mafic end member. In contrast, TH lavas (e.g., Okmok and Westdahl volcanoes) have high FeO/MgO ratios and contain little evidence for mixing. Evolved lavas represent advanced stages of low pressure crystallization from a basaltic magma. These lavas contain groundmass olivine (FO 40 50) and lack Ca-poor pyroxene. Aleutian volcanic rocks with intermediate FeO/MgO ratios are termed transitional tholeiitic (TTH) and calc-alkaline (TCA). TCA magmas are common (e.g., Moffett, Adagdak, Great Sitkin, and Kasatochi volcanoes) and have resulted from mixing of high-Al basalt with more evolved magmas. They contain amphibole (high and low-Al) or orthopyroxene or both and are similar to the Japanese hypersthene-series. TTH magmas (e.g., Okmok and Westdahl) contain orthopyroxene or pigeonite or both, and show some indication of upper crustal mixing. They are mineralogically similar to the Japanese pigeonite-series. High-Al basalt lacks Mg-rich mafic phases and is a derivative magma produced by high pressure fractionation of an olivine tholeiite. The low pressure mineral assemblage of high-Al basalt results from crystallization at higher crustal levels.

  19. 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)

  20. A “Lucan Effect” in the Commitment of Iranian Converts in Transit. The case of the Pentecostal Iranian Enclave in Istanbul

    Directory of Open Access Journals (Sweden)

    Johan Leman

    2012-03-01

    Full Text Available Conversions are not uncommon among transit migrants towards the West. Christian churches, above all Pentecostalism, act as enclaves, also in Islamic countries. They offer a foothold and prospects for the future, in brief: hope. The newcomer grows towards a rebirth. Given that, fundamentally, both the transit migrant and the religious community are transnationally oriented, the convert ultimately discovers a new continuity between past, present and future. The more intensively he participates in the life in his Christian enclave, the more he approaches his initial objective (i.e. migration to the West.  It is a paradox like that illustrated by the parable in Luke 19:17. Hence our suggestion of a  “Lucan effect”, one that naturally calls for an empirically-based, rational explanation in a scientific article.

  1. Formación de un sistema productivo: los enclaves forestales de la región chaqueño-misionera (Siglos XIX-XX

    Directory of Open Access Journals (Sweden)

    Bitlloch, Ruben E.

    2012-08-01

    Full Text Available The purpose of this paper is to describe the development process of a form of production organization centered on the timber-yerba mate mill and the sawmill-tannin factory. This kind of activity developed in the North East of Argentina during the last decades of the 19th century and the first half of the 20th century. The term enclave is used to designate these hubs of activity with a spatial as well as a socio-economical meaning. They tended to set up a kind of physical isolation or spatial enclosure. These enclaves spread out on lands that had been recently appropriated to the indigenous communities. There they built up a territorial domain to which they gave a certain configuration that changed as the conditions of the original form of production organization developed.

    El propósito de este trabajo es el de describir el proceso de desarrollo de una forma de organización de la producción que, teniendo como núcleo al obraje maderero-yerbatero y al aserradero-fábrica de tanino, tuvo lugar durante las últimas décadas del siglo XIX y la primera mitad del siglo XX en el nordeste Argentino. La denominación de enclave que le adjudicamos a estos núcleos de actividad posee un significado espacial y socio-económico ya que se caracterizaron por establecer una suerte de aislamiento físico o clausura espacial. Estos enclaves se explayaron espacialmente en un área recientemente apropiada a las comunidades indígenas configurando un dominio territorial al cual le fueron otorgando cierta configuración que fue cambiando al alterarse las condiciones en que se desenvolvía la forma de organización de la producción que le dio origen.

  2. Do laser/LED phototherapies influence the outcome of the repair of surgical bone defects grafted with biphasic synthetic microgranular HA + β-tricalcium phosphate? A Raman spectroscopy study.

    Science.gov (United States)

    Soares, Luiz Guilherme Pinheiro; Marques, Aparecida Maria Cordeiro; Aciole, Jouber Mateus Santos; da Guarda, Milena Góes; Cangussú, Maria Cristina Teixeira; Silveira, Landulfo; Pinheiro, Antonio Luiz Barbosa

    2014-09-01

    The treatment of bone loss is difficult. Many techniques are proposed to improve repair, including biomaterials and, recently, phototherapies. This work studied bone mineralization by Raman spectroscopy assessing intensities of Raman peaks of both inorganic (∼ 960, ∼ 1,070 cm(-1)) and organic (∼ 1,454 cm(-1)) contents in animal model. Six groups were studied: clot, laser, light-emitting diode (LED), biomaterial (HA + β-tricalcium phosphate), laser + biomaterial, and LED + biomaterial. Defects at right tibia were performed with a drill. When indicated, defects were further irradiated at a 48-h interval during 2 weeks. At the 15th and 30th days, the tibias were withdrawn and analyzed. The ∼ 960-cm(-1) peak was significantly affected by phototherapy on both clot- and biomaterial-filled defects. The ∼ 1,070-cm(-1) peak was affected by both time and the use of the LED light on clot-filled defects. On biomaterial-filled defects, only the use of the laser light significantly influenced the outcome. No significant influence of either the time or the use of the light was detected on clot-filled defects as regards the ∼ 1,454-cm(-1) peak. Raman intensities of both mineral and matrix components indicated that the use of laser and LED phototherapies improved the repair of bone defects grafted or not with biphasic synthetic microgranular HA + β-tricalcium phosphate.

  3. Biochemical changes on the repair of surgical bone defects grafted with biphasic synthetic micro-granular HA + β-tricalcium phosphate induced by laser and LED phototherapies assessed by Raman spectroscopy

    Science.gov (United States)

    Pinheiro, Antonio Luiz B.; Soares, Luiz Guilherme P.; Marques, Aparecida Maria C.; Silveira, Landulfo

    2016-03-01

    This work aimed the assessment of the biochemical changes during bone mineralization induced by laser and LED irradiation in an animal model of bone repair using a spectral model based on Raman spectroscopy. Six groups were studied: Clot, Laser (λ780 nm, 70 mW), LED (λ850 nm +/- 10 nm, 150 mW), Biomaterial (biphasic synthetic microgranular hydroxyapatite (HA) + β-tricalcium phosphate), Laser + Biomaterial and LED + Biomaterial. When indicated, defects were further irradiated at 48 h interval during 2 wks, 20 J/cm2 per session. At 15th and 30th days, femurs were dissected and spectra of the defects were collected. Raman spectra were submitted to a model to estimate the relative amount of collagen, phosphate HA and carbonate HA, by using spectra of pure collagen, biomaterial and basal bone, respectively. At 15th days, the use of biomaterial associated to phototherapy reduced the collagen formation, whereas the amount of carbonate HA was not different in all groups. The phosphate HA was higher in the groups that received biomaterial grafts. At 30th days, it was observed an increase of collagen for the group Laser + Biomaterial, and a reduction in the carbonate HA for the LED + Biomaterial. The phosphate HA was higher for the groups LED + Biomaterial and Laser + Biomaterial, while decreased for the group Biomaterial. These results indicated that the use of Laser and LED phototherapies improved the repair of bone defects grafted with the biomaterial by increasing the collagen deposition and phosphate HA.

  4. Enclaves of opportunity or "ghettos of last resort?" Assessing the effects of immigrant segregation on violent crime rates.

    Science.gov (United States)

    Feldmeyer, Ben; Harris, Casey T; Scroggins, Jennifer

    2015-07-01

    A growing body of research indicates that immigration to the U.S. has crime-reducing effects on aggregate levels of violence, which researchers have often attributed to the protective and revitalizing effects of immigrants settling in spatially concentrated neighborhoods. However, recent scholarship suggests that growing shares of the foreign-born population are bypassing these segregated immigrant enclaves and are dispersing more widely to other urban neighborhoods. Moreover, some scholars suggest that spatially isolating immigrant populations may not always be protective, but could actually contribute to social problems like crime, particularly in disadvantaged contexts. The current study offers one of the first analyses exploring the way that segregation of immigrant populations (relative to the U.S.-born) is related to year 2000 violent crime rates for nearly 500 census places in California and New York. Results of our analysis reveal no direct link between immigrant segregation and macro-level violence, but instead show that these effects are highly contextualized and depend on the resources present in locales. Specifically, immigrant segregation contributes to violence in highly disadvantaged places but is linked to lower violence in areas with greater resources. Copyright © 2015 Elsevier Inc. All rights reserved.

  5. Geochemistry and geodynamics of the Mawat mafic complex in the Zagros Suture zone, northeast Iraq

    Science.gov (United States)

    Azizi, Hossein; Hadi, Ayten; Asahara, Yoshihiro; Mohammad, Youssef Osman

    2013-12-01

    The Iraqi Zagros Orogenic Belt includes two separate ophiolite belts, which extend along a northwest-southeast trend near the Iranian border. The outer belt shows ophiolite sequences and originated in the oceanic ridge or supra-subduction zone. The inner belt includes the Mawat complex, which is parallel to the outer belt and is separated by the Biston Avoraman block. The Mawat complex with zoning structures includes sedimentary rocks with mafic interbedded lava and tuff, and thick mafic and ultramafic rocks. This complex does not show a typical ophiolite sequences such as those in Penjween and Bulfat. The Mawat complex shows evidence of dynamic deformation during the Late Cretaceous. Geochemical data suggest that basic rocks have high MgO and are significantly depleted in LREE relative to HREE. In addition they show positive ɛ Nd values (+5 to+8) and low 87Sr/86Sr ratios. The occurrence of some OIB type rocks, high Mg basaltic rocks and some intermediate compositions between these two indicate the evolution of the Mawat complex from primary and depleted source mantle. The absence of a typical ophiolite sequence and the presence of good compatibility of the source magma with magma extracted from the mantle plume suggests that a mantle plume from the D″ layer is more consistent as the source of this complex than the oceanic ridge or supra-subduction zone settings. Based on our proposed model the Mawat basin represents an extensional basin formed during the Late Paleozoic to younger along the Arabian passive margin oriented parallel to the Neo-Tethys oceanic ridge or spreading center. The Mawat extensional basin formed without creation of new oceanic basement. During the extension, huge volumes of mafic lava were intruded into this basin. This basin was squeezed between the Arabian Plate and Biston Avoraman block during the Late Cretaceous.

  6. Hydrogeochemistry of deep groundwaters of mafic and ultramafic rocks in Finland

    International Nuclear Information System (INIS)

    Ruskeeniemi, T.; Blomqvist, R.; Lindberg, A.; Ahonen, L.; Frape, S.

    1996-12-01

    The present work reports and interprets the hydrogeochemical and hydrogeological data obtained from deep groundwaters in various mafic-ultramafic formations in Finland. The work is mainly based on the results of the research project 'Geochemistry of deep groundwaters' financed by the Ministry of Trade and Industry and the Geological Survey of Finland. Five sites were selected for this study: (1) Juuka, (2) Keminmaa, (3) Maentsaelae, (4) Ranua, and (5) Ylivieska. Keminmaa and Ranua are located in Early Proterozoic layered intrusions dated at 2.44 Ga. The Juuka site lies within the massive Miihkali serpentinite, which is thought to represent the ultramafic part of a Proterozoic (1.97 Ga) ophiolite complex. The Maentsaelae gabbro represents the deep parts of the Svecofennian volcanic sequence, while the Ylivieska mafic-ultramafic intrusion is one of a group of Svecokarelian Ni-potential intrusions 1.9 Ga in age. For reference, groundwaters from four other sites are also briefly described. Three of these sites are located within the nickel mining regions of Enonkoski, Kotalahti and Vammala, while the fourth is a small Ni mineralization at Hyvelae, Noormarkku. The four reference sites are all of Svecokarelian age. (refs.)

  7. Rare-earth element geochemistry in the Luanga Mafic-Ultramafic Complex, Para

    International Nuclear Information System (INIS)

    Suita, M.T.F.; Nilson, A.A.

    1989-01-01

    Six whole-rock samples (harzburgite, orthopyroxenic and norite) of the Luanga Mafic-Ultramafic Complex (Para) were analysed for rare-earth elements (REE) through plasma spectrometry. The Luanga Complex is a deformed and metamorphosed layered mafic-ultramafic body of Archaean age. The Complex underwent medium-grade metamorphism in three stages. The first stage (medium grade) involved local formation of tremolite and reduction of Ca content in plagioclase. The second stage (low grade) consisted of serpentinization of amphibole or ortopyroxene forming bastile and generation of albite + epidote + white mica + actinolite from plagioclase. The third stage involved renewed serpentinization and/or talcification of pre-existing minerals (including serpentine) along fracture and fault surfaces. The analysed rocks display light rare-earth element (LREE) enrichment up to sixty times the composition of the Leedly chondrite and La/Yb ratios from 6.2 to 20.0 they are low in medium rare-earth elements (MREE), displaying discrete to strong negative Eu anomaly even in plagioclase cumulates and are slightly enriched in heavy rare-earth elements (HREE), usually higher than chondrite values. The low MREE area related to the occurrence of orthopyroxene (bronzite) in a way similar to the pattern of alpine periodotites, while HREE enrichment is compatible with the presence of bronzite and Mg-olivine, probably an inherited igneous feature. (author) [pt

  8. Hydrogeochemistry of deep groundwaters of mafic and ultramafic rocks in Finland

    Energy Technology Data Exchange (ETDEWEB)

    Ruskeeniemi, T.; Blomqvist, R.; Lindberg, A.; Ahonen, L. [Geological Survey of Finland, Espoo (Finland); Frape, S. [Waterloo Univ., ON (Canada)

    1996-12-01

    The present work reports and interprets the hydrogeochemical and hydrogeological data obtained from deep groundwaters in various mafic-ultramafic formations in Finland. The work is mainly based on the results of the research project `Geochemistry of deep groundwaters` financed by the Ministry of Trade and Industry and the Geological Survey of Finland. Five sites were selected for this study: (1) Juuka, (2) Keminmaa, (3) Maentsaelae, (4) Ranua, and (5) Ylivieska. Keminmaa and Ranua are located in Early Proterozoic layered intrusions dated at 2.44 Ga. The Juuka site lies within the massive Miihkali serpentinite, which is thought to represent the ultramafic part of a Proterozoic (1.97 Ga) ophiolite complex. The Maentsaelae gabbro represents the deep parts of the Svecofennian volcanic sequence, while the Ylivieska mafic-ultramafic intrusion is one of a group of Svecokarelian Ni-potential intrusions 1.9 Ga in age. For reference, groundwaters from four other sites are also briefly described. Three of these sites are located within the nickel mining regions of Enonkoski, Kotalahti and Vammala, while the fourth is a small Ni mineralization at Hyvelae, Noormarkku. The four reference sites are all of Svecokarelian age. (refs.).

  9. Biochemical changes on the repair of surgical bone defects grafted with biphasic synthetic micro-granular HA + β-tricalcium phosphate induced by laser and LED phototherapies and assessed by Raman spectroscopy.

    Science.gov (United States)

    Pinheiro, Antônio Luiz Barbosa; Soares, Luiz Guilherme Pinheiro; Marques, Aparecida Maria Cordeiro; Cangussú, Maria Cristina Teixeira; Pacheco, Marcos Tadeu Tavares; Silveira, Landulfo

    2017-04-01

    This work aimed the assessment of biochemical changes induced by laser or LED irradiation during mineralization of a bone defect in an animal model using a spectral model based on Raman spectroscopy. Six groups were studied: clot, laser (λ = 780 nm; 70 mW), LED (λ = 850 ± 10 nm; 150 mW), biomaterial (biphasic synthetic micro-granular hydroxyapatite (HA) + β-tricalcium phosphate), biomaterial + laser, and biomaterial + LED. When indicated, defects were further irradiated at a 48-h interval during 2 weeks (20 J/cm 2 per session). At the 15th and 30th days, femurs were dissected and spectra of the defects were collected. Raman spectra were submitted to a model to estimate the relative amount of collagen, phosphate HA, and carbonate HA by using the spectra of pure collagen and biomaterials composed of phosphate and carbonate HA, respectively. The use of the biomaterial associated to phototherapy did not change the collagen formation at both 15 and 30 days. The amount of carbonate HA was not different in all groups at the 15th day. However, at the 30th day, there was a significant difference (ANOVA, p = 0.01), with lower carbonate HA for the group biomaterial + LED compared to biomaterial (p biomaterial grafts at the 15th day compared to clot (significant for the biomaterial; p biomaterial + laser, while this was lower for all the other groups. These results indicated that the use of laser phototherapy improved the repair of bone defects grafted with the biomaterial by increasing the deposition of phosphate HA.

  10. Influence of the λ780nm laser light on the repair of surgical bone defects grafted or not with biphasic synthetic micro-granular hydroxylapatite+Beta-Calcium triphosphate.

    Science.gov (United States)

    Soares, Luiz Guilherme P; Marques, Aparecida Maria C; Guarda, Milena G; Aciole, Jouber Mateus S; dos Santos, Jean Nunes; Pinheiro, Antonio Luiz B

    2014-02-05

    The treatment of bone loss due to different etiologic factors is difficult and many techniques aim to improve repair, including a wide range of biomaterials and, recently, photobioengineering. This work aimed to assess, through histological analysis The aim of this study was to assess, by light microscopy, the repair of bone defects grafted or not with biphasic synthetic micro-granular Calcium hydroxyapatite (HA)+Beta-TCP associated or not with Laser phototherapy - LPT (λ780nm). Forty rats were divided into 4 groups each subdivided into 2 subgroups according to the time of sacrifice (15 and 30days). Surgical bone defects were made on femur of each animal with a trephine drill. On animals of Clot group the defect was filled only by blood clot, on Laser group the defect filled with the clot was further irradiated. On animals of Biomaterial and Laser+Biomaterial groups the defect was filled by biomaterial and the last one was further irradiated (λ780nm, 70mW, spot size∼0.4cm(2), 20J/cm(2)-session, 140J/cm(2)-treatment) in four points around the defect at 48-h intervals and repeated for 2weeks. At both 15th and 30th days following sacrifice, samples were taken and analyzed by light microscopy. Many similarities were observed histologically between groups on regards bone reabsorption and neoformation, inflammatory infiltrate and collagen deposition. The criterion degree of maturation, marked by the presence of basophilic lines, indicated that the use of LPT associated with HA+Beta TCP graft, resulted in more advanced stage of bone repair at the end of the experiment. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. Transnacionalismo y enclave territorial étnico en la configuración de la ciudadanía de los inmigrantes peruanos en Santiago de Chile

    OpenAIRE

    José Carlos Luque Brazán

    2004-01-01

    El presente artículo, aborda el surgimiento de un enclave territorial de inmigrantes peruanos en Santiago de Chile durante 1991 – 2004, e relación a los factores que permiten explicar este fenómeno (discriminación, actores políticos inmigrantes, identidad cultural y el régimen democrático chileno), y las implicancias de este fenómeno en el desarrollo del transnacionalismo político de dichos actores, referidos básicamente a la construcción de una concepción incipiente de ciudadanía transnacio...

  12. Magma Mixing, Mingling and Its Accompanying Isotopic and Elemental Partitioning: Records from Titanites in Guojialing-type Granodiorites and Dioritic Enclaves, Jiaodong, North China

    Science.gov (United States)

    Jiang, P.; Yang, K. F.; Fan, H. R.; Liu, X.

    2016-12-01

    The grain-scale textural and in-situ compositional analyses on accessory minerals (such as titanite, rutile, apatite, monazite, etc.) have recently been a hot topic for geologists, through which a detailed information on magmatic, metamorphic or hydrothermal process can be extracted. As an attempt to unravel the petrogenesis of Early Cretaceous Guojialing-type granodiorites and their bearing dioritic enclaves, we accomplished an integrated geochronological and geochemical study on titanites within these rocks. Three types of titanites, with distinguishable textural and geochemical features, are identified. G-type titanites (from granodiorites) and E-type-I titanites (from plagioclase-rich dioritic enclaves) yield identical U-Pb age of 130 Ma, but reveal distinct back-scattered electron (BSE) zonings. G-type titanites are characterized by oscillatory zonings whereas E-type-I titanites are marked by core-mantle-rim zonings, exhibiting drastic but contrary variation trends for several key elements (such as LREEs, Zr, Hf and F) among their transition BSE zones. These two types of titanites are interpreted to crystallize coevally, and record a notable temperature and compositional change of two corresponding melts, as a response to magma mixing. E-type-II titanites (from plagioclase-poor dioritic enclaves) yield a relatively younger U-Pb age at 128 Ma, and show typical interstitial growth with narrower and lower range of Zr, total REEs contents, but higher F content and Nb/Ta ratios. Such titanites are perceived to record late-stage mingling, during which F-rich and REE-poor hybrid granodioritic magma squeezed into the incompletely consolidated dioritic enclaves with accompanying fluid-rock interaction. Unlike the dramatic elemental changes in these differentiated titanites, in-situ Nd isotopic compositions are relatively homogeneous, which in our view is a good sign of showing that isotopic equilibrium among two magma systems was more easily reached compared to

  13. Physical volcanology of the mafic segment of the subaqueous New Senator caldera, Abitibi greenstone belt, Quebec, Canada

    International Nuclear Information System (INIS)

    Moore, Lyndsay N; Mueller, Wulf U

    2008-01-01

    Archean calderas provide valuable insight into internal geometries of subaqueous calderas. The New Senator caldera, Abitibi greenstone belt, Canada, is an Archean example of a subaqueous nested caldera with a basal stratigraphy dominated by gabbro-diorite dykes and sills, ponded magmas and basalt and andesite lava flows. The aim of our study is to focus on the use of physical volcanology to differentiate between the various mafic units found at the base of the New Senator caldera. Differentiation between these various mafic units is important from an exploration point of view because in modern subaqueous summit calders (e.g. Axial Seamount) margins of ponded magmas are often sites of VMS formation.

  14. Physical volcanology of the mafic segment of the subaqueous New Senator caldera, Abitibi greenstone belt, Quebec, Canada

    Energy Technology Data Exchange (ETDEWEB)

    Moore, Lyndsay N; Mueller, Wulf U [Universite du Quebec a Chicoutimi, 555 boul. du l' Universite, Chicoutimi, Quebec, G7H2B1 (Canada)], E-mail: lyndsay.moore@uqac.ca

    2008-10-01

    Archean calderas provide valuable insight into internal geometries of subaqueous calderas. The New Senator caldera, Abitibi greenstone belt, Canada, is an Archean example of a subaqueous nested caldera with a basal stratigraphy dominated by gabbro-diorite dykes and sills, ponded magmas and basalt and andesite lava flows. The aim of our study is to focus on the use of physical volcanology to differentiate between the various mafic units found at the base of the New Senator caldera. Differentiation between these various mafic units is important from an exploration point of view because in modern subaqueous summit calders (e.g. Axial Seamount) margins of ponded magmas are often sites of VMS formation.

  15. El enclave urbano, lógica socioespacial de la periferia urbanizada y sus efectos sobre la segregación residencial y la fragmentación urbana

    Directory of Open Access Journals (Sweden)

    Guénola Capron

    2016-08-01

    Full Text Available The production of the metropolitan peripheries in Latin America has been characterized by the development of urban, residential and commercial enclaves. These enclaves encompass both large urban housing projects of social interest and subdivisions and gated communities for high-income populations. Both peripheries respond to very different social reasons but have a common spatial logic: the enclave, which deepens the isolation and social distance with its surroundings, generating segregation and fragmentation. We seek to rescue the social and spatial processes of ‘enclosing’ or ‘insularity’ in two cases: a gated community in the northeast — Zona Esmeralda— and a social housing urban complex in the east —San Buenaventura—, both bordering the metropolitan area of the Mexico Valley

  16. 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.

  17. Storage conditions of the mafic and silicic magmas at Cotopaxi, Ecuador

    Science.gov (United States)

    Martel, Caroline; Andújar, Joan; Mothes, Patricia; Scaillet, Bruno; Pichavant, Michel; Molina, Indira

    2018-04-01

    The 2015 reactivation of the Cotopaxi volcano urges us to understand the complex eruptive dynamics of Cotopaxi for better management of a potential major crisis in the near future. Cotopaxi has commonly transitioned from andesitic eruptions of strombolian style (lava flows and scoria ballistics) or nuées ardentes (pyroclastic flows and ash falls) to highly explosive rhyolitic ignimbrites (pumiceous pyroclastic flows), which entail drastically different risks. To better interpret geophysical and geochemical signals, Cotopaxi magma storage conditions were determined via existing phase-equilibrium experiments that used starting materials chemically close to the Cotopaxi andesites and rhyolites. The results suggest that Cotopaxi's most mafic andesites (last erupted products) can be stored over a large range of depth from 7 km to ≥16 km below the summit (pressure from 200 to ≥400 MPa), 1000 °C, NNO +2, and contain 4.5-6.0±0.7 wt% H2O dissolved in the melt in equilibrium with 30-40% phenocrysts of plagioclase, two pyroxenes, and Fe-Ti oxides. These mafic andesites sometimes evolve towards more silicic andesites by cooling to 950 °C. Rhyolitic magmas are stored at 200-300 MPa (i.e. 7-11 km below the summit), 750 °C, NNO +2, and contain 6-8 wt% H2O dissolved in a nearly aphyric melt (<5% phenocrysts of plagioclase, biotite, and Fe-Ti oxides). Although the andesites produce the rhyolitic magmas by fractional crystallization, the Cotopaxi eruptive history suggests reactivation of either reservoirs at distinct times, likely reflecting flux or time fluctuations during deep magma recharge.

  18. Genesis of Soils Formed from Mafic Igneous Rock in the Atlantic Forest Environment

    Directory of Open Access Journals (Sweden)

    Adailde do Carmo Santos

    2016-01-01

    Full Text Available ABSTRACT Different parent materials participate in the formation of soils in the hilly landscape of “Mar de Morros” in the Atlantic Forest environment. Those derived from mafic igneous rock (gabbro frequently show erosion problems because of land use, which is aggravated by the mountainous relief and soil attributes. This study evaluated the main pedogenic processes of soils formed from mafic igneous rock (gabbro in a toposequence in Pinheiral (RJ by characterizing physical, chemical, mineralogical and micromorphological attributes. The profiles are located at different sections in the toposequence: summit (P1, shoulder (P2, backslope (P3 and footslope (P4.They were classified according to the Brazilian System of Soil Classification (SiBCS and correlated to Soil Taxonomy. The soil morphology of profiles P2, P3 and P4 is expressed by a brownish-red color, blocky structure with high to moderate development, clay films and clay loam to clay texture, with a textural B horizon. P1 shows less development, with a shallow profile and the sequence of horizons A-C-Cr. The soils have a slightly low degree of weathering, identified by the presence of pyroxenes and feldspars in the sand fraction and montorillonite in the clay fraction; the sum of bases is from 15 to 24 cmolc kg-1; and cation exchange capacity (CEC is from 12 to 22 cmolc kg-1. A significant presence of clay skins was observed in the field and was confirmed by thin section analysis, which showed features such as argillans, ferriargillans and iron nodules. The soil profile at the summit (P1 was classified as Neossolo Regolítico Órtico (Typic Udorthents, and the other profiles as Chernossolo Argilúvicos Órticos (Typic Argiudolls.

  19. Socio spatial adaptation as a resilience form of native unplanned settlement in confrontation with new planned settlement development pressure (case study: enclave native settlement in Serpong, Tangerang)

    Science.gov (United States)

    Ischak, Mohammad; Setioko, Bambang; Nurgandarum, Dedes

    2017-12-01

    Urban growth refers to expansion of a metropolitan into sub urban areas as the surrounding environment, with no exception of Jakarta city due to limited availability and high price of land within the city. The city of Jakarta, as a metropolitan, carries of expansion in its surrounding environment including Tangerang. Privat developers may an important role in this urban growth through their large scale of new settlement development project. The formation of establishment of enclave native unplanned sub urban settlement scattered within planned new settlement in Tangerang is to be an consequence of Jakarta urban growth. This fenomena could be comprehended as a form of resilience native settlement in confrontation with the new planned settlement pressure. The aim of this research, presented in this paper is to understand the socio-spatial concept of those enclave native settlement as an adaptation form to the new planned settlement pressure. Through descriptive qualitative research method, with indepth interview as a main research instrument, this research could depict or uncover the facts that there are various form of socio-spatial adaptation as the main theme of resilience native suburban settlement formation.

  20. O enclave lingüístico de Xálima: unha análise sociolingüística

    Directory of Open Access Journals (Sweden)

    Fernando Ramallo

    2011-01-01

    Full Text Available This paper presents preliminary results from research into the current sociolinguistic situation in the three areas that make up the Val de Xálima (Extremadura, Spain. Since the Middle Ages three linguistic varieties pertaining to the Galician-Portuguese language system have existed in this area. This community constitutes a sociolinguistic laboratory in which to observe the behaviour of languages in contact (i.e. the local varieties and Spanish, with regard to issues such as identity construction, social cohesion, language maintenance and loss. The aim of this paper is to present an analysis of practices, attitudes and ideologies in this linguistic community, especially among the young population, to determine what factors promote ongoing local variety maintenance. The data were collected through a questionnaire.The results of the study suggest that, unlike many community enclaves, the Valley shows very high indicators of language vitality because of continued intergenerational transmission as well as the community’s deep-rooted appreciation of local speech varieties. However, the linguistic vitality of this enclave is now challenged by accelerating economic growth and increasingly intensive trade with outside areas ensuing from structural changes in the region over the past two decades.

  1. Study on Nd and Sr isotopes of Yianshanian mafic rocks in east Lanling area and their implication

    International Nuclear Information System (INIS)

    Zhang Shuming; Wu Jianhua; Zhou Weixun

    2003-01-01

    East Nanling's Yianshanian mafic magna activity can be divided into four phase. The four phase are the Middle Jurassic, the Late Jurassic, the Early Cretaceous and the Late Cretaceous. They are also four important episodes of extensional activities. The four phase mafic rock possess similar Nd-Sr isotope characteristics, high I Sr (commonly from 0.705 to 0.710) and ε Nd values change range wide (from -7.90 to 5.16). It shows crust-mantle mixed magma origin character. The mafic rock possess the character of within-plate basalts,indicated that they are formed within-plate, and showed there were post-orogenic phase at the early Yianshanian's Middle Jurassic in east Nanling area. The rocks formed pattern is mafic magma rise to the crust bottom, were contaminate by crustal materials, and formed in the setting of lithosphere extended and crust extension. East Nanling's Yianshanian magna activity is mainly magma event concern with mantle magma underplating. (authors)

  2. Geochemistry of Late Mesozoic mafic dykes in western Fujian Province of China:Sr-Nd isotope and trace element constraints

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The Bancun diabase dyke and the Bali hornblende gabbro dyke in western Fuiian Province were emplaced in the Early and Late Cretaceous periods,respectively;the former is designated to calc-alkaline series and the latter to K-high-calc-alkaline rock series.Both the dykes are characterized by such geochemical characteristics as high Al and Na2O>K2O.As for the Bancun dyke,A12O3=16.32%-17.54%and K2O/Na2O=0.65-0.77;as for the Bali dyke,A12O3=16.89%-17.81%and K2O,Na2O=O.93-O.99.Both the Bancun and Bali mafic dykes are relatively endched in LILE and LREE,but depleted in HSFE, displaying the geochemical characteristics of continental marginal arc,with high initial Sr isotopic ratios and low εNd values,The (87Sr/86Sr)i ratios of the Bancun diabase dyke are within the range of 0.708556-0.70903 and their εNd(t)values vary between-6.8 and-6.3;those of the Bali hornblende dyke are within the range of 0.708556-0.710746 and their εNd(t) values are -4.7--4.7,showing the characteristics of enriched mantle EM Ⅱ.The isotope and trace element data showed that the mafic dykes have not experienced obvious crustal contamination,and metasomatism caused by subduction fluids is the main factor leading to LILE and UREE enrichments.The enriched mantle is the source region for the mafic dykes,and mixing of subduction fluid metasomatized enriched mantle and EM Ⅱ-type mantle constituted the mantle source region of both the Bancun and Bali mafic dykes.Upwelling of the asthenosphere mantle provided sufficient heat energy for the generation of magmas.In accordance with the discrimination diagram of their tectonic settings as well as their trace element geochemical characteristics,it is considered that the dykes both at Bancun and Bali possess the characteristics of continental marginal arc,revealing the tectonic environment of formation of the mafic dykes,the continental dynamic background as an intraplate tensional belt in which the mafic dykes were emplaced.Meanwhile,it is also indicated

  3. Mobile Security Enclaves

    Science.gov (United States)

    2011-09-01

    and A8 algorithm contained within the SIM are used for authenticating the MCD to the MSC and for specific sessions, respectively. The A5 algorithm is...using the A5 algorithm initialized by the Kc and the number of the frame to be encrypted. 4. MCD Applications Applications are computer software...an icon from the list of applications on the device. The application opens to the first screen (Figure 5). This screen has two options for the

  4. The genesis of Mo-Cu deposits and mafic igneous rocks in the Senj area, Alborz magmatic belt, Iran

    Science.gov (United States)

    Nabatian, Ghasem; Li, Xian-Hua; Wan, Bo; Honarmand, Maryam

    2017-11-01

    The geochemical and isotopic investigations were provided on the Upper Eocene Senj mafic intrusion and Mo-Cu mineralization to better understand the tectono-magmatic evolution and metallogeny of the central part of the Alborz magmatic belt. The Senj mafic intrusion is composed of gabbro to monzodiorite and monzonite in lithology, and intruded as a sill into volcano-sedimentary rocks of the Eocene Karaj Formation. The Karaj Formation consists of volcano-sedimentary rocks, such as altered crystalline to shaly tuffs. The Senj intrusion (39.7 ± 0.4 Ma) shows LILE and LREE enrichment and negative anomaly of Nb, Ta and Ti, the geochemical signatures similar to those from subduction-related mafic magmas. The Hf-O zircon analyses yield ɛHf(t) values of + 4.1 to + 11.1 and δ18O values of + 4.8 to + 6.2‰. The zircon isotopic signatures together with shoshonitic affinity in the Senj mafic samples suggest partial melting of an enriched lithospheric mantle that had already been metasomatized by slab-derived melts and fluids. The Mo-Cu mineralization mainly occurs as veins and veinlets in the volcano-sedimentary rocks of the Karaj Formation and is dominated by molybdenite with minor amounts of chalcopyrite, bornite, pyrite and tetrahedrite-tennantite. The associated gangue minerals are tremolite, actinolite, quartz, calcite, chlorite and epidote. The Senj Mo-Cu deposit formed in volcano-sedimentary rocks following the emplacement of the Late Eocene Senj sill. The source of molybdenite in the Senj deposit is dominantly from crustal materials as it is revealed by Re contents in the molybdenite minerals (0.5 to 0.7 ppm). In fact, the molybdenite occurrence may be a remobilization process related to the emplacement of the Senj mafic magma.

  5. Geochemical and isotopic evidence for Carboniferous rifting: mafic dykes in the central Sanandaj-Sirjan zone (Dorud-Azna, West Iran

    Directory of Open Access Journals (Sweden)

    Shakerardakani Farzaneh

    2017-06-01

    Full Text Available In this paper, we present detailed field observations, chronological, geochemical and Sr–Nd isotopic data and discuss the petrogenetic aspects of two types of mafic dykes, of alkaline to subalkaline nature. The alkaline mafic dykes exhibit a cumulate to foliated texture and strike NW–SE, parallel to the main trend of the region. The 40Ar/39Ar amphibole age of 321.32 ± 0.55 Ma from an alkaline mafic dyke is interpreted as an indication of Carboniferous cooling through ca. 550 °C after intrusion of the dyke into the granitic Galeh-Doz orthogneiss and Amphibolite-Metagabbro units, the latter with Early Carboniferous amphibolite facies grade metamorphism and containing the Dare-Hedavand metagabbro with a similar Carboniferous age. The alkaline and subalkaline mafic dykes can be geochemically categorized into those with light REE-enriched patterns [(La/YbN = 8.32–9.28] and others with a rather flat REE pattern [(La/YbN = 1.16] and with a negative Nb anomaly. Together, the mafic dykes show oceanic island basalt to MORB geochemical signature, respectively. This is consistent, as well, with the (Tb/YbPM ratios. The alkaline mafic dykes were formed within an enriched mantle source at depths of ˃ 90 km, generating a suite of alkaline basalts. In comparison, the subalkaline mafic dykes were formed within more depleted mantle source at depths of ˂ 90 km. The subalkaline mafic dyke is characterized by 87Sr/86Sr ratio of 0.706 and positive ɛNd(t value of + 0.77, whereas 87Sr/86Sr ratio of 0.708 and ɛNd(t value of + 1.65 of the alkaline mafic dyke, consistent with the derivation from an enriched mantle source. There is no evidence that the mafic dykes were affected by significant crustal contamination during emplacement. Because of the similar age, the generation of magmas of alkaline mafic dykes and of the Dare-Hedavand metagabbro are assumed to reflect the same process of lithospheric or asthenospheric melting. Carboniferous back-arc rifting is

  6. The Mafic Lower Crust of Neoproterozoic age beneath Western Arabia: Implications for Understanding African Lower Crust

    Science.gov (United States)

    Stern, R. J.; Mooney, W. D.

    2011-12-01

    ) and Cr (435 vs. 117 ppm). Despite high Mg# in pyroxene-rich xenoliths, mineral compositions of labradoritic plagioclase (mean ~An64) and relatively Fe-rich pyroxenes (mean OPX ~En63; mean CPX~ WO48 En35 Fs17) indicate that these are somewhat fractionated. Trace element patterns are similar to those expected for convergent-margin magmatic suites. Nd-model ages define a mean of 0.76±0.08 Ga, similar to the age of exposed Arabian Shield upper crust. An isochron plot (147Sm/144Nd vs. 143Nd/144Nd) is consistent with formation in Neoproterozoic time. Lower crust of Arabia clearly formed during Neoproterozoic time, about the same time as its upper crust complement; a similar origin for the lower crust beneath the broad expanses of Neoproterozoic crust in N and E Africa is likely. There is no evidence that any of the mafic lower crust of Arabia formed due to underplating by Cenozoic magmas, which may also be true for NE Africa and perhaps mafic lower crust on the flanks of the East African Rift. Such an interpretation predicts a strong lower crust for those regions underlain by anhydrous mafic lower crust of Neoproterozoic age.

  7. Petrogenesis of the Alaskan-type mafic-ultramafic complex in the Makkah quadrangle, western Arabian Shield, Saudi Arabia

    Science.gov (United States)

    Habtoor, Abdelmonem; Ahmed, Ahmed Hassan; Harbi, Hesham

    2016-10-01

    The Makkah quadrangle is a part of the Jeddah terrane in the Precambrian basement, Western Arabian Shield of Saudi Arabia. Gabal Taftafan mafic-ultramafic complex lies within the central part of the Makkah quadrangle. The Taftafan mafic-ultramafic complex is a well-differentiated rock association which comprises of dunite core, hornblende- and plagioclase-bearing peridotites, troctolite, clinopyroxenite and marginal gabbro, in a distinctive zonal structure. The bulk-rock geochemistry of the Taftafan mafic-ultramafic rocks is characterized by a tholeiitic/sub-alkaline affinity with high Mg in the ultramafic core (0.84) and is systematically decreased towards the marginal gabbro (0.60). The patterns of trace elements show enrichment in the fluid-mobile elements (Sr, Ba) and a pronounced negative Nb anomaly which reflect a hydrous parental magma generated in a subduction tectonic setting. The mafic-ultramafic rocks of the Taftafan complex have low total rare earth elements (REE) displaying sub-parallel patterns leading to the assumption that these rocks are comagmatic and are formed by fractional crystallization from a common magma type. The platinum-group elements (PGE) content of all rock types in the Taftafan complex is very low, with ∑ PPGE > ∑ IPGE; displaying slightly positive slopes of the PGE distribution patterns. The chemistry of ferromagnesian minerals is characterized by a high forsterite (Fo) olivine with wide range (Fo91-67), from ultramafic core to the marginal gabbro, Ca-rich diopsidic clinopyroxene, and calcic hornblende. Orthopyroxene is almost absent from all rock types, or very rare when present. Hornblende and Ca-plagioclase possess the longest crystallization history since they are present in almost all rock types of the complex. Spinels in the dunite and hornblende-bearing peridotite core show homogeneous composition with intermediate Cr# (0.53-0.67). Plagioclase-bearing peridotite and troctolite have two exsolved types of spinel; Al

  8. Organización y Demandas del Movimiento Obrero en Centroamérica: Entre el Enclave Bananero y el Proceso de Reformas Sociales

    Directory of Open Access Journals (Sweden)

    Yesenia Martínez García

    2014-01-01

    Full Text Available El surgimiento de las plantaciones bananeras y de los movimientos son procesos acompasados en la historia de Centroamérica y el Caribe de América Latina durante la primera mitad del Siglo XX. Lo que a continuación se expone es un panorama general sobre la organización y las agendas del movimiento obrero en Centroamérica desde un análisis historiográfico. Se trata de hilvanar los diferentes planteamientos y casos en la región; se contextualiza en la injerencia de los Estados Unidos y sus intereses económicos y políticos en Centroamérica, en un segundo periodo de la Reforma Liberal, y las conexiones con un Estado Moderno y Social. La historiografía centroamericana aporta mucho a esta problemática más desde enfoques económicos y políticos; han sido los académicos estadounidenses y costarricenses quienes más se han interesado por analizar la problemática desde perspectivas sociales y culturales. Ahora, tratamos de presentar un panorama comparativo, desde lo social.Palabras Clave: Centroamérica; Movimiento Obrero; Enclave Bananero y Reformas Sociales.Organization and Claims of Labor Movement in Central America: Between the Enclave Banana and Social ReformsAbstractThe emergence of the banana plantations and the movements are rhythmic processes in the history of Central America and the Caribbean Latin America during the first half of the twentieth century. What then is exposed is an overview of the organization and the agendas of the labor movement in Central America from a historiographical analysis. It is to weave the different approaches and cases in the region is contextualized in the interference of the United States and its economic and political interests in Central America, in a second period of liberal reform, and connections with a Modern State and Social. American historiography to this problem provides much more from economic and political approaches, scholars have been Americans and Costa Ricans who have been most

  9. Cl-rich hydrous mafic mineral assemblages in the Highiș massif, Apuseni Mountains, Romania

    Science.gov (United States)

    Bonin, Bernard; Tatu, Mihai

    2016-08-01

    The Guadalupian (Mid-Permian) Highiș massif (Apuseni Mountains, Romania) displays a bimodal igneous suite of mafic (gabbro, diorite) and A-type felsic (alkali feldspar granite, albite granite, and hybrid granodiorite) rocks. Amphibole is widespread throughout the suite, and yields markedly high chlorine contents. Three groups are identified: Cl-rich potassic hastingsite (2.60-3.40 wt% Cl) within A-type felsic rocks and diorite, mildly Cl-rich pargasite to hornblende (0.80-1.90 wt% Cl) within gabbro, and low F-Cl hornblende within gabbro and hybrid granodiorite. Coexisting biotite is either Cl-rich within diorite, or F-Cl-poor to F-rich within A-type felsic rocks. Chlorine and fluorine are distributed in both mafic phases, according to the F-Fe and Cl-Mg avoidance rules. The low-Ti contents suggest subsolidus compositions. Cl-rich amphibole within diorite and A-type felsic rocks yields a restricted temperature range - from 575 °C down to 400 °C, whereas mildly Cl-rich amphibole within gabbro displays the highest range - from 675 to 360 °C. Temperatures recorded by Cl-rich biotite within diorite range from 590 to 410 °C. Biotite within A-type felsic rocks yields higher temperatures than amphibole: the highest values- from 640 to 540 °C - are recorded in low-F-Cl varieties, whereas the lowest values- from 535 to 500 °C - are displayed by F-rich varieties. All data point to halogen-rich hydrothermal fluids at upper greenschist facies conditions percolating through fractures and shear zones and pervasively permeating the whole Highiș massif, with F precipitating as interstitial fluorite and Cl incorporating into amphibole, during one, or possibly several, hydrothermal episodes that would have occurred during a ~ 150 My-long period of time extending from the Guadalupian (Mid-Permian) to the Albian (Mid-Cretaceous).

  10. Geophysical evidence for an extensive Pie de Palo Complex mafic-ultramafic belt, San Juan, Argentina

    Science.gov (United States)

    Chernicoff, Carlos J.; Vujovich, Graciela I.; van Staal, Cees R.

    2009-12-01

    The recent completion of a high-resolution aeromagnetic survey over the Pie de Palo uplift of the western Sierras Pampeanas has revealed an area of large magnetic anomalies associated with the Pie de Palo Complex. The Las Pirquitas thrust, which has transported and uplifted the Pie de Palo Complex, is recognized for at least 30 km in a roughly NE direction along the western boundary of the Pie de Palo Complex, beyond its limited outcrop. The type of sediments of the Caucete Group in the footwall of the Las Pirquitas thrust, which are regarded as the leading edge of the Precordillera terrane, are associated with much less pronounced magnetic anomalies. In addition, a conspicuous, NNE trending, broad magnetic high stands out in the survey, several kilometers to the east of the main outcrops of the Pie de Palo Complex; this broad magnetic anomaly bisects the Pie de Palo basement block, and continues further south at least as far as 32°S, the southern boundary of the latest aeromagnetic survey. This magnetic anomaly is interpreted to represent a structure corresponding to the Grenvillian Precordillera-Pie de Palo tectonic boundary zone, and would comprise the buried largest part of the mafic-ultramafic belt. The geophysical model of the magnetic data indicates that the boundary zone dips to the east, possibly suggesting the existence of a set of synthetic east dipping, west-verging thrusts, of which only one major structure (Las Pirquitas thrust) is exposed; the possibility of other slivers of upthrust boundary zone material cannot be excluded. It is considered that the Pie de Palo Complex represents a small sliver upthrust from the unexposed boundary zone material (containing highly magnetic mafic-ultramafic rocks). The east-dipping, west verging structures associated with the Pie de Palo Complex are suggested to represent an Ordovician reactivation of a Grenvillian suture zone developed when the Precordillera basement and Pie de Palo terrane docked; this

  11. Petrogenesis and U-Pb and Sm-Nd geochronology of the Taquaral granite: record of an orosirian continental magmatic arc in the region of Corumba - MS

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    Letícia Alexandre Redes

    Full Text Available The Taquaral Granite is located on southern Amazon Craton in the region of Corumbá, westernmost part of the Brazilian state of Mato Grosso do Sul (MS, near Brazil-Bolivia frontier. This intrusion of batholitic dimensions is partially covered by sedimentary rocks of the Urucum, Tamengo Bocaina and Pantanal formations and Alluvial Deposits. The rock types are classified as quartz-monzodiorites, granodiorites, quartz-monzonites, monzo and syenogranites. There are two groups of enclaves genetically and compositionally different: one corresponds to mafic xenoliths and the second is identified as felsic microgranular enclave. Two deformation phases are observed: one ductile (F1 and the other brittle (F2. Geochemical data indicate intermediate to acidic composition for these rocks and a medium to high-K, metaluminous to peraluminous calk-alkaline magmatism, suggesting also their emplacement into magmatic arc settings. SHRIMP zircon U-Pb geochronological data of these granites reveals a crystallization age of 1861 ± 5.3 Ma. Whole rock Sm-Nd analyses provided εNd(1,86 Ga values of -1.48 and -1.28 and TDM model ages of 2.32 and 2.25 Ga, likely indicating a Ryacian crustal source. Here we conclude that Taquaral Granite represents a magmatic episode generated at the end of the Orosirian, as a part of the Amoguija Magmatic Arc.

  12. Geochronology and geochemistry of mafic dykes from the precambrians of Keonjhar, Orissa

    Energy Technology Data Exchange (ETDEWEB)

    Mallik, A K; Sarkar, Amitabha [Geological Survey of India, Calcutta (India). Geochronology and Isotope Geology Division

    1994-01-01

    Two generations of mafic dolerite dykes with distinct geochemical signatures are recorded in the Champua-Keonjhargarh area of Keonjhar district in the eastern Indian precambrian craton (EIPC) on the basis of geochemical and K-Ar isotopic studies. The younger group-II dykes (ca. 1250 Ma) are mostly Fe-tholeiities, whereas the older group-I dykes (2100 +/- 100 Ma) show a wider compositional spectrum from Mg-Fe tholeiites to komatiitic basalts. The group-I dolerites show higher MgO content, Mg value. CaO/(Na){sub 2}O + K{sub 2}O and lower Fe{sub 2}O{sub 3}(T) and TiO{sub 2} contents compared to those in the group-II dykes. Consistent with their comparatively evolved nature, the group-II dolerites have lower Cr, Ni, total REE, Rb/Sr ratio and incompatible element abundances than those in the group-I dolerite rocks. Both the generations of dolerites, however, reveal enrichment in compatible elements and in this respect are similar to proterozoic dykes elsewhere in the world. Both groups of dykes reveal Fe-enrichment trend typical of tholeiitic intrusions in the FMA diagram- a feature mimicked by plots in the (Y + Zr) - 100 x TiO{sub 2} - Cr diagram. The available isotopic age data pertaining to the newer dolerite suite of Singhbhum - Keonjhar region of the EIPC are reviewed. (author). 29 refs., 15 figs., 4 tabs.

  13. Silicate geothermometry as an indicator of water-rock interaction processes in the serpentinized mafic-ultramafic intrusion of Ylivieska

    International Nuclear Information System (INIS)

    Ruskeeniemi, T.; Blomqvist, R.; Vuorela, P.; Frape, S.K.; Blyth, A.

    1996-01-01

    The aim of the study was to use oxygen and hydrogen isotopes to examine the origin of different generations of serpentine. Of special interest was the study of low-temperature generations that may be correlated with the present meteoric waters. The research was commenced with drill core logging in order to obtain insight into the fracture minerals and their distribution in a mafic-ultramafic intrusion. (39 refs., 17 figs., 5 tabs.)

  14. Paleomagnetism of Early Cambrian Itabaiana mafic dikes (NE Brazil) and the final assembly of Gondwana

    Science.gov (United States)

    Trindade, Ricardo I. F.; D'Agrella-Filho, Manoel S.; Epof, Igor; Brito Neves, Benjamim B.

    2006-04-01

    Paleomagnetic analysis on 15 early Cambrian mafic dikes from Itabaiana (Paraíba State) yielded a southern (northwestern) direction with steep upward (downward) inclination ( Dm = 167.5°, Im = - 63.7°, α95 = 7.3°). AF and Thermal demagnetization, thermomagnetic curves, and hysteresis results suggest that this component is dominantly carried by fine-grained SD magnetite. The high stability of this component and positive baked contact tests on three dikes indicate it represents a primary thermoremanent magnetization. Ar-Ar analysis on whole-rock samples from two sites provides a strong constraint on the age of the Itabaiana paleomagnetic pole (134.6° E, 34.9° S; A95 = 7.3, K = 28) defined by plateau ages of 525 ± 5 and 526 ± 4 Ma. This pole completely satisfies six out of the seven quality criteria proposed by Van der Voo [R. Van der Voo, The reliability of paleomagnetic data, Tectonophysics 184 (1990) 1-9.] and permits a tight constraint on the Early Cambrian sector of the Gondwana apparent polar wander path. Paleogeographic reconstructions consistent with the available paleomagnetic and geological record show that Gondwana was sutured along three major orogenies, the Mozambique (Brasilano/Pan-African) Orogeny (800-650 Ma), the Kuunga Orogeny (570-530 Ma) and the Pampean-Araguaia Orogeny (540-520 Ma). We suggest that after rifting away from Laurentia at the end of the Neoproterozoic, opening the Iapetus ocean, the Amazonian craton and minor adjoining blocks, such as Rio Apa and Pampia, collided with the proto-Gondwana by Cambrian times at ca. 530-520 Ma. Unless for small adjustments, Gondwana was completely formed by 525 Ma whose paleogeography is defined by the Itabaiana pole.

  15. Shallow magma diversions during explosive maar-diatreme eruptions in mafic volcanic fields

    Science.gov (United States)

    Le Corvec, N.; Muirhead, J.; White, J. D. L.

    2017-12-01

    Maar-diatremes are inverted conical structures formed by subterranean excavation and remobilization of country rocks during explosive volcanism and common in mafic volcanic fields. We focus on impacts of excavation and filling of maar-diatremes on the local state of stress, and its subsequent influence on underlying feeder dikes, which are critical for understanding the development of intrusive networks that feed surface eruptions. We address this issue using finite element models in COMSOL Multiphysics®. Inverted conical structures of varying sizes are excavated in a gravitationally loaded elastic half-space, and then progressively filled with volcaniclastic material, resulting in changes in the orientations and magnitudes of stresses generated within surrounding rocks and within the filling portion of the maar-diatreme. Our results show that rapid unloading during maar-diatreme excavation generates a horizontal compressive stress state beneath diatremes. These stresses allow magma to divert laterally as saucer-shaped sills and circumferential dikes at varying depths in the shallow feeder system, and produce intrusion geometries consistent with both field observations from exhumed volcanic fields and conceptual models of diatreme growth. Stresses generated in these models also provide an explanation for the evolving locations of fragmentation zones over the course of diatreme's filling. In particular, results from this study suggest that: (1) extensional stresses at the base of the diatreme fill favor magma ascent in the lower half of the structure, and possibly promote volatile exsolution and magma fragmentation; and (2) increased filling of diatremes creates a shallow compressive stress state that can inhibit magma ascent to the surface, promoting widespread intra-diatreme explosions, efficient mixing of host rock, and upward widening of the diatreme structure.

  16. Effects of interaction between ultramafic tectonite and mafic magma on Nd-Pb-Sr isotopic systems in the Neoproterozoic Chaya Massif, Baikal-Muya ophiolite belt

    Science.gov (United States)

    Amelin, Yuri V.; Ritsk, Eugeni Yu.; Neymark, Leonid A.

    1997-04-01

    Sm-Nd, Rb-Sr and U-Pb isotopic systems have been studied in minerals and whole rocks of harzburgites and mafic cumulates from the Chaya Massif, Baikal-Muya ophiolite belt, eastern Siberia, in order to determine the relationship between mantle ultramafic and crustal mafic sections. Geological relations in the Chaya Massif indicate that the mafic magmas were emplaced into, and interacted with older solid peridotite. Hand picked, acid-leached, primary rock-forming and accessory minerals (olivine, orthopyroxene, clinopyroxene and plagioclase) from the two harzburgite samples show coherent behavior and yield 147Sm/ 144Nd- 143Nd/ 144Nd and 238U/ 204Pb- 206Pb/ 204Pb mineral isochrons, corresponding to ages of 640 ± 58 Ma (95% confidence level) and 620 ± 71 Ma, respectively. These values are indistinguishable from the crystallization age of the Chaya mafic units of 627 ± 25 Ma (a weighted average of internal isochron Sm-Nd ages of four mafic cumulates). The Rb-Sr and Sm-Nd isotopic systems in the harzburgite whole-rock samples were disturbed by hydrothermal alteration. These alteration-related isotopic shifts mimic the trend of variations in primary isotopic compositions in the mafic sequence, thus emphasizing that isotopic data for ultramafic rocks should be interpreted with great caution. On the basis of initial Sr and Nd values, ultramafic and mafic rocks of the Chaya Massif can be divided into two groups: (1) harzburgites and the lower mafic unit gabbronorites withɛ Nd = +6.6 to +7.1 andɛ Sr = -11 to -16; and (2) websterite of the lower unit and gabbronorites of the upper mafic unit:ɛ Nd = +4.6 to +6.1 andɛ Sr = -8 to -9. Initial Pb isotopic ratios are identical in all rocks studied, with mean values of 206Pb/ 204Pb= 16.994 ± 0.023 and 207Pb/ 204Pb= 15.363 ± 0.015. The similarity of ages and initial isotopic ratios within the first group indicates that the isotopic systems in the pre-existing depleted peridotite were reset by extensive interaction with

  17. Large Igneous Provinces, Their Giant Mafic Dyke Swarms, and Links to Metallogeny

    Science.gov (United States)

    Jowitt, S.; Ernst, R. E.

    2017-12-01

    The relationships between large igneous provinces (LIPs), their giant dyke swarms and differing metallogenic systems can be condensed into five distinct although partially overlapping classifications: (1) LIP magmas that directly generate mineral deposits such as orthomagmatic Ni-Cu-PGE sulfides. Many carbonatites (Nb, Ta REE deposits) and kimberlites (diamonds) are also often LIP related. On the other hand, LIP-related thermal pulses (from a mantle plume) can sometimes destroy diamond potential in the overlying lithosphere. A key locus for Ni-Cu-PGE mineralization is within a few hundred km of the plume center region and plume centers are best located using giant radiating dyke swarms. Dyke subswarms with chalcophile element depletions can also be tracked "upstream" toward the plume center to identify exploration targets. (2) LIP magmas that provide energy, fluids, and/or metals for ore types such as hydrothermal volcanogenic massive sulfide (VMS) and iron oxide-copper-gold (IOCG) deposits. Heat loss from the margins of dykes and sills can also generate local enrichments in key metals (e.g. Co) within the surrounding sedimentary rocks. (3) LIP rocks (particularly sills and dykes) can act barriers to fluid flow and/or as reaction zones that control mineralizing events, act as structural traps within hydrocarbon systems, and form impermeable barriers that control water flow and hence aquifer formation (4) surficial effects, such as the formation of Ni-Co laterites and Al bauxites from tropical weathering of LIP mafic-ultramafic rocks (including volcanics fed by radiating dykes as well as the dykes themselves). This category also includes LIP-related anoxia events that generate hydrocarbon source rocks; and (5) indirect links between LIPs and ore deposits, where continental breakup-related LIP events define a `barcode' record (usually dominated by dyke swarms) that can be used to correlate and reconstruct Precambrian supercontinents. This fifth classification type

  18. Mg isotope systematics during magmatic processes: Inter-mineral fractionation in mafic to ultramafic Hawaiian xenoliths

    Science.gov (United States)

    Stracke, A.; Tipper, E. T.; Klemme, S.; Bizimis, M.

    2018-04-01

    , the clearly resolvable inter-mineral Mg isotope differences imply that crystallization or preferential melting of isotopically distinct minerals such garnet, spinel, and clinopyroxene should cause Mg isotope fractionation between bulk melt and residue. Calculated Mg isotope variations during partial mantle melting indeed predict differences between melt and residue, but these are analytically resolvable only for melting of mafic lithologies, that is, garnet pyroxenites. Contributions from garnet pyroxenite melts may thus account for some of the isotopically light δ26Mg observed in ocean island basalts and trace lithological mantle heterogeneity. Consequently, applications for high-temperature Mg isotope fractionations are promising and diverse, and recent advances in analytical precision may allow the full petrogenetic potential inherent in the sub per mill variations in δ26Mg in magmatic rocks to be exploited.

  19. Inferences of Present and Past Changes at Isolated Enclaves and Matrix of Savannas by Carbon Isotopes in a Transitional Forest-Savanna Area in Northern Amazonia

    Science.gov (United States)

    Couto-Santos, F. R.; Luizao, F. J.; Camargo, P. B.

    2013-12-01

    The evolutionary history of savannas influenced by short term climate cycles, during the Quaternary Period, could prompt variations in forest cover often related to movements of the forest-savanna boundary. In this study we investigated current and past changes in the structure of vegetation and the origins of savannas of different natures in a biogeographically and climatic transitional forest-savanna area in northern Amazonia. Variations in the isotopic composition of soil organic matter (δ13C) from surface soils (0-10 cm) along forest-savanna boundaries, detected by a sigmoidal non-linear function, were used to identify current changes in vegetation, while past changes were inferred by discontinuities in the evolution of δ13C with soil depth using piecewise regression associated with radiocarbon dating (14C). By comparing small isolated savanna enclaves inside a strictly protected nature reserve (ESEC Maracá) with its outskirts unprotected continuous savanna matrix, we found that origins and the patterns of dynamics were distinct between these areas and did not respond in the same way to climate change and fire events, either in the last decades or during the Holocene. The stability of the present boundaries of the surrounding savanna matrix reflects the resilience of the transitional forests under a recent intensified fire regime and favorable climate, while the deep forest soil isotopic signal indicated a forest shrinkage of at least 70 m occurring since its origin in early Holocene until 780 years BP associated with a climate drier than the current one. Contrarily, the protected enclaves inside ESEC Maracá, remained stable since the middle Holocene, suggesting a non-anthropogenic origin related to soil edaphic conditions, but with recent dynamics of advancing forest by 8 m century-1 favored by current climate and lacking fire events. A detailed understanding of the origins of savannas of distinct natures and the way they are affected by climate and fire

  20. 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

  1. Rb-Sr and Nd-Sr isotope geochemistry and petrogenesis of the Misho Mountains mafic dikes (NW Iran

    Directory of Open Access Journals (Sweden)

    Maryam Ahankoub

    2017-02-01

    Full Text Available Introduction There are some theories about the Paleotethys event during the Paleozoic that have been proposed by geologists (Metcalfe, 2006. Some scientist offered some pieces of evidence about the northern margin of Gondwana (Zhu et al., 2010. The Paleotethys Ocean and Hercynian orogenic report first in Iran, have been Offered from the Morrow and Misho Mountain (Eftekharnejad, 1981. Misho Mountains is located between the north and south Misho faults and cause the formation of a positive flower structure (Moayyed and Hossainzade, 2011. There is theory about Misho southern fault as the best candidate of the Paleotethys suture zone (Moayyed and Hossainzade, 2011. Geochemistry and Sr –Nd isotopic data of the A2 granitic and Synite rocks of the East Misho, indicate that the magmatism post collision has occurred in the active continental margin by extensional zones of the following the closure of the Paleotethys (Ahankoub, 2012. Granite and syenite rocks have been cut by mafic dikes. Mafic dikes are often formed in extensional tectonic settings related to mantle plume or continental break –up (Zhu et al., 2009. In this paper, we use the geochemistry and Nd-Sr isotope data to determined petrogenesis, tectono-magmatic setting and age of Misho mafic dikes. Materials and methods After petrography study of 30 thin sections of mafic dike rocks, 8 samples were selected for whole-rock chemical analyses using ICP-MS and ICP-AES instruments by ACME Company in Vancouver, Canada. We prepared 6 sample For Sm-Nd and Rb-Sr analysis. Sr and Nd isotope ratios were measured with a thermal ionization mass spectrometer, VG Sector 54–30 at the Nagoya University. The isotope abundances of Rb, Sr, Nd, and Sm were measured by the ID method with a Finnigan MAT Thermoquad THQ thermal ionization quadrupole mass spectrometer at the Nagoya University. NBS987 and JNdi-1 were measured as natural Sr and Nd isotope ratio standards (Tanaka et al., 2000. Averages and 2σ errors

  2. The timing of compositionally-zoned magma reservoirs and mafic 'priming' weeks before the 1912 Novarupta-Katmai rhyolite eruption

    Science.gov (United States)

    Singer, Brad S.; Costa, Fidel; Herrin, Jason S.; Hildreth, Wes; Fierstein, Judith

    2016-01-01

    The June 6, 1912 eruption of more than 13 km3 of dense rock equivalent (DRE) magma at Novarupta vent, Alaska was the largest of the 20th century. It ejected >7 km3 of rhyolite, ~1.3 km3 of andesite and ~4.6 km3 of dacite. Early ideas about the origin of pyroclastic flows and magmatic differentiation (e.g., compositional zonation of reservoirs) were shaped by this eruption. Despite being well studied, the timing of events that led to the chemically and mineralogically zoned magma reservoir remain poorly known. Here we provide new insights using the textures and chemical compositions of plagioclase and orthopyroxene crystals and by reevaluating previous U-Th isotope data. Compositional zoning of the magma reservoir likely developed a few thousand years before the eruption by several additions of mafic magma below an extant silicic reservoir. Melt compositions calculated from Sr contents in plagioclase fill the compositional gap between 68 and 76% SiO2 in whole pumice clasts, consistent with uninterrupted crystal growth from a continuum of liquids. Thus, our findings support a general model in which large volumes of crystal-poor rhyolite are related to intermediate magmas through gradual separation of melt from crystal-rich mush. The rhyolite is incubated by, but not mixed with, episodic recharge pulses of mafic magma that interact thermochemically with the mush and intermediate magmas. Hot, Mg-, Ca-, and Al-rich mafic magma intruded into, and mixed with, deeper parts of the reservoir (andesite and dacite) multiple times. Modeling the relaxation of the Fe-Mg concentrations in orthopyroxene and Mg in plagioclase rims indicates that the final recharge event occurred just weeks prior to the eruption. Rapid addition of mass, volatiles, and heat from the recharge magma, perhaps aided by partial melting of cumulate mush below the andesite and dacite, pressurized the reservoir and likely propelled a ~10 km lateral dike that allowed the overlying rhyolite to reach the surface.

  3. Geochemical characteristics of granitoids and related mafic granulites from the Pan-African Dahomeyide belt, southeastern Ghana

    International Nuclear Information System (INIS)

    Aidoo, F.

    2012-07-01

    The Dahorneyide orogenic belt marks the southeastern limit of the West Africa craton (WAC). The belt consists of three structural units which include the deformed eastern edge of the WAC with its cover rocks made up of the Togo and the Buern Structural Units (external nappes), a suture zone assemblage of mafic and ultramafic rocks, and granitoid gneiss-rnigmatite assemblages (east of the suture zone). Geochemical and petrographic characteristics of the granitoids from the external nappes and mafic and ultramafic granulites roeks from the suture zone have been studied with the objective of inferring their petrogenesis and tectonic setting in which they were formed. Twenty five (25) representative samples were selected for petrographic studies and fifteen samples for major and trace elements composition using ICP-AES and ICP-MS respectively. The granitoids gneisses are mainly biotite muscovite gneisses, migmatites and granodiorites made up of quartz (25-68%), biotite (7-30%), plagioclase (8-40%), muscovite (4-20%) with some few pyroxene, sericite and calcite observed in some oF the samples. Within these rocks is an amphibole rich gneiss composed of about 45% amphiboles. The granitoid gneisses contain SiO 2 content of 40.60-68.90 wt. % with low Mg# of 36-46. Geochernically, they are classified as I-type, mctaluminous to peraluminous, magnessian to ferroan, calcic to calc alkali granitoids. They exhibit fractionated REE patterns with (La/Sm) N = 1.80-5.85 and (La/Yb) N = 3.76-76.30, and negative to positive Eu anomalies (Eu/Eu*'' = 0.68-2.10. The primitive mantle-normalised, trace element patterns show that the granitoid gneisses are characterised by enrichment in LILE relative to HFSE and in LREE relative HREE. They display subduction-related trace element characteristics of positive Ba and negative Ti, Ta, Nb and Hf anomalies. The mafic granulites are composed of quartz (16-43%), hornblende (12-45%), plagioclase (13-23%), pyroxene (13-17%), garnet (4

  4. Early Jurassic mafic dykes from the Aigao uranium ore deposit in South China: Geochronology, petrogenesis and relationship with uranium mineralization

    Science.gov (United States)

    Zhang, Di; Zhao, Kui-Dong; Chen, Wei; Jiang, Shao-Yong

    2018-05-01

    Mafic dykes are abundant and widely distributed in many granite-hosted uranium ore deposits in South China. However, their geochronology, petrogenesis and relationship with uranium mineralization were poorly constrained. In this study, apatite U-Pb dating, whole-rock major and trace element and Sr-Nd-Pb isotope analysis were conducted for the dolerite dykes from the Aigao uranium ore deposit. Apatite U-Pb isotopic data indicate that the mafic dykes were emplaced at Early Jurassic (189 ± 4 Ma), which provides new evidence for the rarely identified Early Jurassic magmatism in South China. Pyroxene from the dykes is mainly augite, and plagioclase belongs to albite. The dolerite samples have relatively low SiO2 contents (45.33-46.79 wt%), relatively high total alkali contents (K2O + Na2O = 4.11-4.58 wt%) and Al2O3 contents (13.39-13.80 wt%), and medium MgO contents (4.29-5.16 wt%). They are enriched in Nb, Ta, Ti, rare earth elements and depleted in Rb, K, Sr, Th, showing the typical OIB-like geochemical affinity. All the dolerite samples show homogeneous Sr-Nd-Pb isotopic compositions, with (87Sr/86Sr)i varying from 0.706049 to 0.707137, εNd(t) from +4.6 to +5.2, 206Pb/204Pb from 19.032 to 19.126 and 207Pb/204Pb from 15.641 to 15.653. The mafic dykes in the Aigao deposit should be derived from the partial melting of the asthenospheric mantle and formed in a within-plate extensional environment. The emplacement age of the mafic dykes is older than the uranium mineralization age. Therefore, CO2 in ore-forming fluids couldn't originate from the basaltic magma as suggested by previous studies. The dolerite dykes might only provide a favorable reducing environment to promote the precipitation of uraninite from oxidize hydrothermal fluids.

  5. Geochemical characteristics and tectonic setting of the Tuerkubantao mafic-ultramafic intrusion in West Junggar, Xinjiang, China

    Directory of Open Access Journals (Sweden)

    Yufeng Deng

    2015-03-01

    Full Text Available Mineral chemistry, whole-rock major oxide, and trace element compositions have been determined for the Tuerkubantao mafic-ultramafic intrusion, in order to understand the early Paleozoic tectonic evolution of the West Junggar orogenic belt at the southern margin of the Central Asian orogenic belt. The Tuerkubantao mafic-ultramafic intrusion is a well-differentiated complex comprising peridotite, olivine pyroxenite, gabbro, and diorite. The ultramafic rocks are mostly seen in the central part of the intrusion and surrounded by mafic rocks. The Tuerkubantao intrusive rocks are characterized by enrichment of large ion lithophile elements and depleted high field strength elements relative to N-MORB. In addition, the Tuerkubantao intrusion displays relatively low Th/U and Nb/U (1.13–2.98 and 2.53–7.02, respectively and high La/Nb and Ba/Nb (1.15–4.19 and 37.7–79.82, respectively. These features indicate that the primary magma of the intrusion was derived from partial melting of a previously metasomatized mantle source in a subduction setting. The trace element patterns of peridotites, gabbros, and diorite in the Tuerkubantao intrusion have sub-parallel trends, suggesting that the different rock types are related to each other by differentiation of the same primary magma. The intrusive contact between peridotite and gabbro clearly suggest that the Tuerkubantao is not a fragment of an ophiolite. However, the Tuerkubantao intrusion displays many similarities with Alaskan-type mafic-ultramafic intrusions along major sutures of Phanerozoic orogenic belts. Common features include their geodynamic setting, internal lithological zoning, and geochemistry. The striking similarities indicate that the middle Devonian Tuerkubantao intrusion likely formed in a subduction-related setting similar to that of the Alaskan-type intrusions. In combination with the Devonian magmatism and porphyry mineralization, we propose that subduction of the oceanic slab has

  6. Study of the mining possibilities in the surroundings of Mahoma - Guaycuru phase I Feasibility of the mafic body of Mahoma-Guaycuru and of the complex mafic - Stratified ultramafic of the Cerros Negros and San Jose and Colonia provinces

    International Nuclear Information System (INIS)

    Coronel, N.; Techera, J.; Ramos, E.; Pineyro, G.

    1990-01-01

    In Mahoma - Guaycuru area has been carried out regional cartography to place the geologic context, mainly the Mahoma bodies magmatic intrusive s, Guaycuru and Cerros Negros. The area has good mining possibilities due to their geologic environment. They exist also geochemical anomalies in the area that they should be taken as base for future works in the same one. In this environment studies were begun with the bodies magmatic mafic and ultramafic, due to its feasibility in Platino ides, Chromium, Nickel, Cobalt . It intent to adjust in a following stage (it Leaves II) a work methodology in an occurrence of minerals metallic. for future works,la occurrence of metallic minerals it lacks elements of economic interest in concentrations high, just as it demonstrates it the geochemical of rocks carried out, and the lack of anomalies in the geochemical of active silts and of floors. As element of interest single Gold appears in samples alluvial deposits but their source would not be the mafic rocks. Other occurrence of metallic minerals appears

  7. 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.

  8. Petrogenetic evolution of the felsic and mafic volcanic suite in the Siang window of Eastern Himalaya, Northeast India

    Directory of Open Access Journals (Sweden)

    A. Krishnakanta Singh

    2012-09-01

    Full Text Available The Abor volcanics outcroping in the core of the Siang window in the Eastern Himalaya comprise voluminous mafic volcanics (47%–56% w(SiO2, with subordinate felsic volcanics (67%–75% w(SiO2. The felsic volcanics are dacitic to rhyolitic in composition and are typically enriched in LREE (La/SmN = 3.09–3.90 with high REE contents (256–588 ppm, moderately fractionated REE patterns (CeN/YbN = 6.54–9.52 and pronounced negative Eu anomalies (Eu/Eu* = 0.55–0.72. Wide variations in Rb/Zr, K/Rb and La/Sm ratios suggest that they were derived from magmas which were randomly contaminated with crustal material. Chemical characteristics and petrogenetic modelling indicate that the dacites were generated by ∼15% partial melting of a mafic source leaving a residue with 55% plagioclase, 14% orthoclase, 18% clinopyroxene, 5% orthopyroxene, 8% hornblende. The silica-rich rhyodacites and rhyolites were derived from a dacite magma source by a higher degree (>45% fractional crystallization of an assemblage consisting of 70% plagioclase, 12% clinopyroxene, 7% amphibole and 11% magnetite. The associated LREE-LILE enrichment and pronounced negative anomalies for HFSE (Nb, P, and Ti exhibited by these felsic volcanics are characteristic of continental rift volcanism, implying that they were emplaced during lithospheric extension.

  9. Geochronology, geochemistry, and petrogenesis of late Permian to early Triassic mafic rocks from Darongshan, South China: Implications for ultrahigh-temperature metamorphism and S-type granite generation

    Science.gov (United States)

    Xu, Wang-Chun; Luo, Bi-Ji; Xu, Ya-Jun; Wang, Lei; Chen, Qi

    2018-05-01

    The role of the mantle in generating ultrahigh-temperature metamorphism and peraluminous S-type granites, and the extent of crust-mantle interaction are topics fundamental to our understanding of the Earth's evolution. In this study we present geochronological, geochemical, and Sr-Nd-Hf isotopic data for dolerites and mafic volcanic rocks from the Darongshan granite complex belt in western Cathaysia, South China. LA-ICP-MS U-Pb zircon analyses yielded magma crystallization ages of ca. 250-248 Ma for the dolerites, which are coeval with eruption of the mafic volcanic rocks, ultrahigh-temperature metamorphism, and emplacement of S-type granites in the Darongshan granite complex belt. The mafic volcanic rocks are high-K calc-alkaline or shoshonitic, enriched in Th, U, and light rare earth elements, and depleted in Nb, Ta and Ti. The dolerites are characterized by high Fe2O3tot (11.61-20.39 wt%) and TiO2 (1.62-3.17 wt%), and low MgO (1.73-4.38 wt%), Cr (2.8-10.8 ppm) and Ni (2.5-11.4 ppm). Isotopically, the mafic volcanic rocks have negative whole-rock εNd(t) values (-6.7 to -9.0) and high ISr values (0.71232 to 0.71767), which are slightly depleted compared with the dolerite samples (εNd(t) = -10.3 to -10.4 and ISr = 0.71796 to 0.71923). Zircons in the dolerites have εHf(t) values of -7.6 to -10.9. The mafic volcanic rocks are interpreted to have resulted from the partial melting of an enriched lithospheric mantle source with minor crustal contamination during ascent, whereas the dolerites formed by late-stage crystallization of enriched lithospheric mantle-derived magmas after fractionation of olivine and pyroxene. The formation of these mantle-derived mafic rocks may be attributed to transtension along a NE-trending strike-slip fault zone that was related to oblique subduction of the Paleo-Pacific plate beneath South China. Such underplated mafic magmas would provide sufficient heat for the generation of ultrahigh-temperature metamorphism and S-type granites, and

  10. Stratigraphy, distribution, and evidence for mafic triggering of the ca. 8.5 ka Driftwood Pumice eruption, Makushin Volcano, Alaska, U.S.A

    Science.gov (United States)

    Lerner, Allan H.; Crowley, Peter D.; Nicolaysen, Kirsten P.; Hazlett, Richard W.

    2018-05-01

    Makushin Volcano on Unalaska Island, Alaska, threatens the Aleutian's largest population centers (Unalaska and Dutch Harbor), yet its eruption mechanisms are poorly known. This study presents a detailed stratigraphic and geochemical investigation of Makushin's most recent highly explosive event: the ca. 8.5 ka Driftwood Pumice eruption. The Driftwood Pumice has measured thicknesses of over 2.5 m, and isopach reconstructions estimate a total deposit volume of 0.3 to 1.6 km3, indicating a VEI 4-5 eruption. Proximal deposits consist of normally-graded, tan, dacitic to andesitic pumice, capped by a thinner dark layer of lower-silica andesitic scoria mixed with abundant lithic fragments. This stratigraphy is interpreted as an initial vent-clearing eruption that strengthened into a climactic ejection of pumice and ash and concluded with vent destabilization and the eruption of somewhat more mafic, gas-poor magma. Within the pumice, geochemical trends, disequilibrium mineral populations, and mineral zonation patterns show evidence of magma mixing between a bulk silicic magma and a mafic melt. Euhedral high-Ca plagioclase (An68-91) and high-Mg olivine (Fo69-77) phenocrysts are in disequilibrium with trachydacitic glass (65-68 wt% SiO2) and more abundant sodic plagioclase (An34-55), indicating the former originally crystallized in a more mafic melt. Tephra whole rock compositions become more mafic upwards through the deposit, ranging from a basal low-silica dacite to an andesite (total range: 60.8-63.3 wt% SiO2). Collectively, these compositional variations suggest magma mixing in the Driftwood Pumice (DWP) magma reservoir, with a systematic increase in the amount of a mafic component (up to 25%) upward through the deposit. Olivine-liquid and liquid-only thermometry indicate the mafic magma intruded at temperatures 140-200 °C hotter than the silicic magma. Diffusion rates calculated for 5-7 μm thick, lower-Mg rims on the olivine phenocrysts (Fo60 rim vs Fo76 bulk) suggest

  11. Multiple remote sensing data sources to assess spatio-temporal patterns of fire incidence over Campos Amazônicos Savanna Vegetation Enclave (Brazilian Amazon).

    Science.gov (United States)

    Alves, Daniel Borini; Pérez-Cabello, Fernando

    2017-12-01

    Fire activity plays an important role in the past, present and future of Earth system behavior. Monitoring and assessing spatial and temporal fire dynamics have a fundamental relevance in the understanding of ecological processes and the human impacts on different landscapes and multiple spatial scales. This work analyzes the spatio-temporal distribution of burned areas in one of the biggest savanna vegetation enclaves in the southern Brazilian Amazon, from 2000 to 2016, deriving information from multiple remote sensing data sources (Landsat and MODIS surface reflectance, TRMM pluviometry and Vegetation Continuous Field tree cover layers). A fire scars database with 30 m spatial resolution was generated using a Landsat time series. MODIS daily surface reflectance was used for accurate dating of the fire scars. TRMM pluviometry data were analyzed to dynamically establish time limits of the yearly dry season and burning periods. Burned area extent, frequency and recurrence were quantified comparing the results annually/seasonally. Additionally, Vegetation Continuous Field tree cover layers were used to analyze fire incidence over different types of tree cover domains. In the last seventeen years, 1.03millionha were burned within the study area, distributed across 1432 fire occurrences, highlighting 2005, 2010 and 2014 as the most affected years. Middle dry season fires represent 86.21% of the total burned areas and 32.05% of fire occurrences, affecting larger amount of higher density tree surfaces than other burning periods. The results provide new insights into the analysis of burned areas of the neotropical savannas, spatially and statistically reinforcing important aspects linked to the seasonality patterns of fire incidence in this landscape. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Charnockitic ortho gneisses and mafic granulites of Cerro Olivo complex, proterozoic basement of SE Uruguay, Part 1: Geology

    International Nuclear Information System (INIS)

    Masquelin, H.

    2008-01-01

    Charnockitic ortho gneisses and mafic granulite s exposed in the Cerro Bori Block, in the center of Punta del Este terrain, were the first document occurrence of granulitic rocks from SE sector of the Uruguayan Shield. We present here their main geological features, with the purpose to suggest some petrologic and structural interesting problems for a future lithogeochemical, mineral chemistry, stable isotopes and fluid inclusion studies about these rocks. We propose some speculation form field-based studies considering a cognate magmatic origin of both kinds of rocks, previous to a homogeneous granulitic metamorphism. Some structural evidences indicate that after their uplift, these rocks were located on over thickened crust, at great to medium deepness. A cataclasis during anatexis and amphibolite-facies mineral association stabilization are common phenomena. Other evidences suggest a polycyclic character for the regional geologic evolution

  13. Spinels of Variscan olivine hornblendites related to the Montnegre granitoids revisited (NE Spain): petrogenetic evidence of mafic magma mixing

    Energy Technology Data Exchange (ETDEWEB)

    Galán, G.; Enrique, P.; Butjosa, L.; Fernández-Roig, L.

    2017-07-01

    Olivine hornblendites (cortlandtites) form part of the Montnegre mafic complex related to late-Variscan I-type granitoids in the Catalan Coastal Ranges. Two generations of spinel are present in these hornblendites: Spl1 forms euhedral crystals included in both olivine and Spl2. Spl2 forms euhedral to anhedral crystals associated with phlogopite and fibrous colourless amphibole forming pseudomorphs after olivine. Compositions of Spl1 are picotite-Al chromite (Fe#: 77.78-66.60; Cr#: 30.12-52.22; Fe3+/R3+: 6.99-21.89; 0.10< TiO2%< 0.62). Compositions of Spl2 are pleonaste (Fe#: 37.86-52.12; Cr#: 1.00-15.45; Fe3+/R3+: 0.31-5.21; TiO2% <0.10%). The two types of spinel follow a CrAl trend, mainly due to the substitution (Fe2+)-1Cr-1= MgAl, which is interpreted as the result of mixing between two different mantle-derived melts. The compositions of early Spl1 crystals included in olivine are characteristic of Al-rich basalts. More aluminous Spl2 would result from reaction of olivine with a less evolved, Al and K-rich mantle-derived melt after new refilling of the magma chamber or channel. As a whole, spinels from similar examples of Variscan olivine hronblendites also follow a CrAl trend with high Fe# and starting at higher Cr# than other trends of this type. Cr# heterogeneity in the early spinels from these Variscan hornblendites would be inherited from the variable Al content of the mafic melts involved in their genesis.

  14. Postmagmatic magnetite-apatite assemblage in mafic intrusions: a case study of dolerite at Olympic Dam, South Australia

    Science.gov (United States)

    Apukhtina, Olga B.; Kamenetsky, Vadim S.; Ehrig, Kathy; Kamenetsky, Maya B.; McPhie, Jocelyn; Maas, Roland; Meffre, Sebastien; Goemann, Karsten; Rodemann, Thomas; Cook, Nigel J.; Ciobanu, Cristiana L.

    2016-01-01

    An assemblage of magnetite and apatite is common worldwide in different ore deposit types, including disparate members of the iron-oxide copper-gold (IOCG) clan. The Kiruna-type iron oxide-apatite deposits, a subtype of the IOCG family, are recognized as economic targets as well. A wide range of competing genetic models exists for magnetite-apatite deposits, including magmatic, magmatic-hydrothermal, hydrothermal(-metasomatic), and sedimentary(-exhalative). The sources and mechanisms of transport and deposition of Fe and P remain highly debatable. This study reports petrographic and geochemical features of the magnetite-apatite-rich vein assemblages in the dolerite dykes of the Gairdner Dyke Swarm (~0.82 Ga) that intruded the Roxby Downs Granite (~0.59 Ga), the host of the supergiant Olympic Dam IOCG deposit. These symmetrical, only few mm narrow veins are prevalent in such dykes and comprise besides usually colloform magnetite and prismatic apatite also further minerals (e.g., calcite, quartz). The genetic relationships between the veins and host dolerite are implied based on alteration in the immediate vicinity (~4 mm) of the veins. In particular, Ti-magnetite-ilmenite is partially to completely transformed to titanite and magmatic apatite disappears. We conclude that the mafic dykes were a local source of Fe and P re-concentrated in the magnetite-apatite veins. Uranium-Pb ages for vein apatite and titanite associated with the vein in this case study suggest that alteration of the dolerite and healing of the fractures occurred shortly after dyke emplacement. We propose that in this particular case the origin of the magnetite-apatite assemblage is clearly related to hydrothermal alteration of the host mafic magmatic rocks.

  15. La accesibilidad a los enclaves logísticos en Castilla y León. Una propuesta metodológica para su medición y evaluación

    Directory of Open Access Journals (Sweden)

    Alejandro López González

    2015-01-01

    Full Text Available Castilla y León es una Comunidad Autónoma en la que la actividad logística adquiere una re-levancia singular. Su situación geográfica entre los puertos marítimos del norte y noroeste en relación al resto de la península, y el hecho de estar atravesada por la principal ruta de comunica-ción entre Portugal y el resto de Europa, han propiciado la consolidación en su espacio regional de una densa red de vías de alta capacidad que la dota de una fuerte conectividad y favorece la actividad logística. En este contexto, la Junta de Castilla y León aplica desde 2006 un modelo de ordenación de dicha actividad logística denominado CyLog, que se apoya en 15 enclaves y cinco grandes ejes o corredores viarios. En este artículo se analizan la eficiencia del Modelo CyLog, las características de los enclaves y la localización de los mismos en relación con la red de corredores de alta capacidad, los puertos y el mercado más relevante vecino a la Comunidad, Madrid, con el objetivo de determinar su importancia para el desarrollo regional y la integración territorial. Para alcanzar este objetivo se propone y aplica una metodología destinada a la medición de la accesibilidad de los enclaves logísticos que conforman CyLog.

  16. Geochronology and Sr–Nd–Hf isotopic composition of the granites, enclaves, and dikes in the Karamay area, NW China: Insights into late Carboniferous crustal growth of West Junggar

    Directory of Open Access Journals (Sweden)

    Di Li

    2015-03-01

    Full Text Available New whole-rock major and trace elements, and zircon U–Pb and Hf–Nd isotope compositions are reported for the Karamay dikes, enclaves, and host granites in the West Junggar, NW China. Zircon U–Pb dating of the Karamay pluton yields an age of 300.7 ± 2.3 Ma for the enclave and 300.0 ± 2.6 Ma for the host granite, which was intruded by dike with an age of 298 Ma. The host granites exhibit relatively low SiO2 contents and A/CNK and Ga/Al ratios, low initial 87Sr/86Sr ratios (0.703421–0.703526 and positive εHf(t (5.5–14.1 and εNd(t (7.3–8.1 values with a young model age, suggesting that they are I-type granites and were mainly derived from a juvenile lower crustal source. The enclaves and dikes belong to an andesitic calc-alkaline series and have high MgO concentrations at low silica content and positive εHf(t (7.6–13.2, 14.2–14.9 and εNd(t (6.8–8.3, ∼6.9 values. They are enriched in LILEs (Rb, Ba and U and LREE and depleted in HFSEs (Nb and Ta with insignificant negative Eu anomalies, indicating that the melts were derived from an enriched lithospheric mantle modified by subducted oceanic crust-derived melts and minor fluids, followed by fractional crystallization. The Karamay host granites and enclaves are of mixed origin and are most probably formed by the interaction between the lower crust- and lithospheric mantle-derived magmas, and were intruded by the unmixed dikes subsequently. The upwelling mantle through a slab window in an island arc environment might have triggered partial melting of the lithospheric mantle and its subsequent interaction with the granitic magma, further suggesting that the ridge subduction played an important role in the crustal growth of West Junggar.

  17. A Thermodynamic Approach for Modeling H2O-CO2 Solubility in Alkali-rich Mafic Magmas at Mid-crustal Pressures

    Science.gov (United States)

    Allison, C. M.; Roggensack, K.; Clarke, A. B.

    2017-12-01

    Volatile solubility in magmas is dependent on several factors, including composition and pressure. Mafic (basaltic) magmas with high concentrations of alkali elements (Na and K) are capable of dissolving larger quantities of H2O and CO2 than low-alkali basalt. The exsolution of abundant gases dissolved in alkali-rich mafic magmas can contribute to large explosive eruptions. Existing volatile solubility models for alkali-rich mafic magmas are well calibrated below 200 MPa, but at greater pressures the experimental data is sparse. To allow for accurate interpretation of mafic magmatic systems at higher pressures, we conducted a set of mixed H2O-CO2 volatile solubility experiments between 400 and 600 MPa at 1200 °C in six mafic compositions with variable alkali contents. Compositions include magmas from volcanoes in Italy, Antarctica, and Arizona. Results from our experiments indicate that existing volatile solubility models for alkali-rich mafic magmas, if extrapolated beyond their calibrated range, over-predict CO2 solubility at mid-crustal pressures. Physically, these results suggest that volatile exsolution can occur at deeper levels than what can be resolved from the lower-pressure experimental data. Existing thermodynamic models used to calculate volatile solubility at different pressures require two experimentally derived parameters. These parameters represent the partial molar volume of the condensed volatile species in the melt and its equilibrium constant, both calculated at a standard temperature and pressure. We derived these parameters for each studied composition and the corresponding thermodynamic model shows good agreement with the CO2 solubility data of the experiments. A general alkali basalt solubility model was also constructed by establishing a relationship between magma composition and the thermodynamic parameters. We utilize cation fractions from our six compositions along with four compositions from the experimental literature in a linear

  18. Field-trip guide to mafic volcanism of the Cascade Range in Central Oregon—A volcanic, tectonic, hydrologic, and geomorphic journey

    Science.gov (United States)

    Deligne, Natalia I.; Mckay, Daniele; Conrey, Richard M.; Grant, Gordon E.; Johnson, Emily R.; O'Connor, Jim; Sweeney, Kristin

    2017-08-16

    The Cascade Range in central Oregon has been shaped by tectonics, volcanism, and hydrology, as well as geomorphic forces that include glaciations. As a result of the rich interplay between these forces, mafic volcanism here can have surprising manifestations, which include relatively large tephra footprints and extensive lava flows, as well as water shortages, transportation and agricultural disruption, and forest fires. Although the focus of this multidisciplinary field trip will be on mafic volcanism, we will also look at the hydrology, geomorphology, and ecology of the area, and we will examine how these elements both influence and are influenced by mafic volcanism. We will see mafic volcanic rocks at the Sand Mountain volcanic field and in the Santiam Pass area, at McKenzie Pass, and in the southern Bend region. In addition, this field trip will occur during a total solar eclipse, the first one visible in the United States in more than 25 years (and the first seen in the conterminous United States in more than 37 years).The Cascade Range is the result of subduction of the Juan de Fuca plate underneath the North American plate. This north-south-trending volcanic mountain range is immediately downwind of the Pacific Ocean, a huge source of moisture. As moisture is blown eastward from the Pacific on prevailing winds, it encounters the Cascade Range in Oregon, and the resulting orographic lift and corresponding rain shadow is one of the strongest precipitation gradients in the conterminous United States. We will see how the products of the volcanoes in the central Oregon Cascades have had a profound influence on groundwater flow and, thus, on the distribution of Pacific moisture. We will also see the influence that mafic volcanism has had on landscape evolution, vegetation development, and general hydrology.

  19. Catchment-wide weathering and erosion rates of mafic, ultramafic, and granitic rock from cosmogenic meteoric 10Be/9Be ratios

    Science.gov (United States)

    Dannhaus, N.; Wittmann, H.; Krám, P.; Christl, M.; von Blanckenburg, F.

    2018-02-01

    Quantifying rates of weathering and erosion of mafic rocks is essential for estimating changes to the oceans alkalinity budget that plays a significant role in regulating atmospheric CO2 levels. In this study, we present catchment-wide rates of weathering, erosion, and denudation measured with cosmogenic nuclides in mafic and ultramafic rock. We use the ratio of the meteoric cosmogenic nuclide 10Be, deposited from the atmosphere onto the weathering zone, to stable 9Be, a trace metal released by silicate weathering. We tested this approach in stream sediment and water from three upland forested catchments in the north-west Czech Republic. The catchments are underlain by felsic (granite), mafic (amphibolite) and ultramafic (serpentinite) lithologies. Due to acid rain deposition in the 20th century, the waters in the granite catchment exhibit acidic pH, whereas waters in the mafic catchments exhibit neutral to alkaline pH values due to their acid buffering capability. The atmospheric depositional 10Be flux is estimated to be balanced with the streams' dissolved and particulate meteoric 10Be export flux to within a factor of two. We suggest a correlation method to derive bedrock Be concentrations, required as an input parameter, which are highly heterogeneous in these small catchments. Derived Earth surface metrics comprise (1) Denudation rates calculated from the 10Be/9Be ratio of the "reactive" Be (meaning sorbed to mineral surfaces) range between 110 and 185 t km-2 y-1 (40 and 70 mm ky-1). These rates are similar to denudation rates we obtained from in situ-cosmogenic 10Be in quartz minerals present in the bedrock or in quartz veins in the felsic and the mafic catchment. (2) The degree of weathering, calculated from the fraction of 9Be released from primary minerals as a new proxy, is about 40-50% in the mafic catchments, and 10% in the granitic catchment. Lastly, (3) erosion rates were calculated from 10Be concentrations in river sediment and corrected for sorting

  20. Solution-mass transfer and grain boundary sliding in mafic shear zones - comparison between experiments and nature

    Science.gov (United States)

    Marti, Sina; Heilbronner, Renée; Stünitz, Holger; Plümper, Oliver; Drury, Martyn

    2017-04-01

    Grain size sensitive creep (GSSC) mechanisms are widely recognized to be the most efficient deformation mechanisms in shear zones. With or without initial fracturing and fluid infiltration, the onset of heterogeneous nucleation leading to strong grain size reduction is a frequently described process for the initiation of GSSC. Phase mixing due to reaction and heterogeneous nucleation during GSSC impedes grain growth, sustaining small grain sizes as a prerequisite for GSSC. Here we present rock deformation experiments on 'wet' plagioclase - pyroxene mixtures at T=800°C, P=1.0 and 1.5GPa and strain rates of 2e-5 - 2e-6 1/s, performed with a Griggs-type solid medium deformation apparatus. Microstructural criteria are used to show that both, grain boundary sliding (GBS) and solution-mass transfer processes are active and are interpreted to be the dominant strain accommodating processes. Displacement is localized within shear bands formed by fine-grained ( 300 - 500nm) plagioclase (Pl) and the syn-kinematic reaction products amphibole (Amph), quartz (Qz) and zoisite (Zo). We compare our experiments with a natural case - a sheared mafic pegmatite (P-T during deformation 0.7 - 0.9 GPa, 610 - 710 °C; Getsinger et al., 2013) from Northern Norway. Except for the difference in grain size of the experimental and natural samples, microstructures are strikingly alike. The experimental and natural P- and especially T-conditions are very similar. Consequently, extrapolation from experiments to nature must be made without a significant 'temperature-time' trade-off, which is normally taken advantage of when relating experimental to natural strain rates. We will discuss under which assumptions extrapolation to nature in our case is likely feasible. Syn-kinematic reactions during GBS and solution-mass transport are commonly interpreted to result in an ordered (anticlustered) phase mixture. However, phase mixing in our case is restricted: Mixing is extensive between Pl + Zo + Qz and

  1. Geological setting, emplacement mechanism and igneous evolution of the Atchiza mafic-ultramafic layered suite in north-west Mozambique

    Science.gov (United States)

    Ibraimo, Daniel Luis; Larsen, Rune B.

    2015-11-01

    The Atchiza mafic and ultramafic-layered suite (hereafter, "Atchiza Suite) crops out in an area 330 km2 west of the Mozambican Tete province. In an early account of the geology of this intrusion, it was considered the continuation of the Great Dyke of Zimbabwe, an idea that was aborted after detailed studies. Nevertheless, the Ni concentrations in the Atchiza outcrop rocks are considerable. Our investigation used field evidence, hand specimens and petrography descriptions, mineral chemistry studies using electron microprobe analysis and tectonic analysis to arrive at a plausible mineralogical composition and understanding of the tectonic setting for the igneous evolution. The mineral composition from the Atchiza Suite indicates that these are cumulates. The magmatic segregation from the petrographic and mineral composition reasoning indicates that dunite-lherzolitic peridotite-olivine gabbro-gabbronorite-gabbro-pegmatitic gabbro is the rock formation sequence. Olivine and chromite were the first phases formed, followed by pyroxene and plagioclase. In addition, it is shown that these minerals are near-liquidus crystallization products of basaltic magma with olivine Fo: 87.06 in dunite, mean values of clinopyroxene are (Wo: 36.4, En: 48.0, Fs: 15.2), orthopyroxene (Wo: 2.95, En: 73.0, Fs: 24.2) and plagioclase An: 71.3, respectively. Opaque minerals comprise Fe-Ti oxides and (Fe, Cr) spinel up to 4.8 vol.%, but chromitite layers are not present. Most of the opaque minerals are interstitial to pyroxene. Sulphides are common in gabbros, with pyrrhotite, pentlandite, chalcopyrite, pyrite and covellite together comprising 0.4-2.0 vol.%. The whole rock Rare Earth Element (REE) concentrations are mainly a result of differentiation, but slight crustal contamination/assimilation contributed to the REE contents. In addition, they also show Eu enrichment, suggesting that plagioclase fractionation was important in the rock. The Atchiza Suite preserves a deep-seated plumbing

  2. Metamorphic P-T path and zircon U-Pb dating of HP mafic granulites in the Yushugou granulite-peridotite complex, Chinese South Tianshan, NW China

    Science.gov (United States)

    Zhang, Lu; Zhang, Lifei; Xia, Bin; Lü, Zeng

    2018-03-01

    Co-existing granulite and peridotite may represent relics of the paleo-suture zone and provides an optimal opportunity for better understanding of orogeny between two blocks. In this study, we carried out petrological and U-Pb zircon dating investigation on the HP mafic granulites associated with peridotite complex at Yushugou in Chinese South Tianshan. The studied samples include garnet-bearing high-pressure mafic granulites which can be subdivided into two types: Type I orthopyroxene-free and Type II orthopyroxene-bearing granulites and amphibolite. Type I granulite (Y21-2) has a mineral assemblage of garnet (33 vol.%), clinopyroxene (32 vol.%) and plagioclase (30 vol.%); and Type II granulite (Y18-8) has a mineral assemblage of garnet (22 vol.%), clinopyroxene (10 vol.%), orthopyroxene (14 vol.%), plagioclase (45 vol.%) and quartz. Garnet in both granulites exhibits core-rim structure characterized by increasing grossular and decreasing pyrope from core to rim. Petrographic observations and phase equilibrium modeling using THERMOCALC in the NCFMASHTO system for the mafic granulites (Y21-2 and Y18-8) show three stages of metamorphism: Stage I (granulite facies) was recognized by the large porphyroblastic garnet core, with P-T conditions of 9.8-10.4 Kbar and 860-900 °C (Y21-2) and 9.9-10.6 Kbar and 875-890 °C (Y18-8), respectively; Stage II (HP granulite facies) has peak P-T conditions of 12.1 Kbar at 755 °C (Y21-2) and 13.8 Kbar at 815 °C (Y18-8) using mineral assemblages combining with garnet rim compositions with maximum grossular and minimum pyrope contents; Stage III (amphibolite facies) was characterized by the development of calcic amphibole in granulites with temperature of 446-563 °C. Therefore, an anticlockwise P-T path characterized by simultaneous temperature-decreasing and pressure-increasing was inferred for the Yushugou HP mafic granulite. Studies of zircon morphology and inclusions, combined with zircon U-Pb dating and REE geochemistry

  3. En-clave de Sol

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    Louis Manfield

    2011-12-01

    Full Text Available Ha pasado más de medio año desde que tuviera lugar el estallido reivindicativo del 16-M y las sucesivas explosiones en las que derivó este movimiento asambleario. Ninguno de los que asistieron a la manifestación del domingo, 15 de mayo, podía imaginarse que estaban pisando el centro de lo que iba a ser el escenario de la protesta colectiva más mediática de este país. Pero la Acampada ha sido algo más que el material de relleno para los medios de (desinformación y trend topic en redes sociales. Para los que nos dedicamos, en este caso, a la sociología, SOL se nos presenta como un juguete. Un sofisticado artefacto (su compleja y espesa red organizativa así lo atestiguan para poner a prueba, in situ y participando, la plasticidad y elasticidad social de la creatividad contestataria que ha convertido a un movimiento definido como indignado en un modelo autónomo de organización horizontal. Una cámara del tiempo donde el corto, el medio y largo plazo se entrecruzan con el corto, medio y largo alcance. Una ventana desde la que observar y anticipar el cambio que ya se está produciendo en el seno de la sociedad.

  4. Fluid Inclusion Study of Quartz Xenocrysts in Mafic Dykes from Kawant Area, Chhota Udaipur District, Gujarat, India

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    Randive Kirtikumar

    2015-09-01

    Full Text Available Unusual mafic dykes occur in the proximity of the Ambadongar Carbonatite Complex, Lower Narmada Valley, Gujarat, India. The dykes contain dense population of quartz xenocrysts within the basaltic matrix metasomatised by carbonate-rich fluids. Plagioclase feldspars, relict pyroxenes, chlorite, barite, rutile, magnetite, Fe-Ti oxides and glass were identified in the basaltic matrix. Quartz xenocrysts occur in various shapes and sizes and form an intricate growth pattern with carbonates. The xenocrysts are fractured and contain several types of primary and secondary, single phase and two-phase fluid inclusions. The two-phase inclusions are dominated by aqueous liquid, whereas the monophase inclusions are composed of carbonic gas and the aqueous inclusions homogenize to liquid between 226°C and 361°C. Majority of the inclusions are secondary in origin and are therefore unrelated to the crystallization of quartz. Moreover, the inclusions have mixed carbonic-aqueous compositions that inhibit their direct correlation with the crustal or mantle fluids. The composition of dilute CO2-rich fluids observed in the quartz xenocrysts appear similar to those exsolved during the final stages of evolution of the Amba Dongar carbonatites. However, the carbonates are devoid of fluid inclusions and therefore their genetic relation with the quartz xenocrysts cannot be established.

  5. Grain to outcrop-scale frozen moments of dynamic magma mixing in the syenite magma chamber, Yelagiri Alkaline Complex, South India

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    M.L. Renjith

    2014-11-01

    Full Text Available Magma mixing process is unusual in the petrogenesis of felsic rocks associated with alkaline complex worldwide. Here we present a rare example of magma mixing in syenite from the Yelagiri Alkaline Complex, South India. Yelagiri syenite is a reversely zoned massif with shoshonitic (Na2O + K2O=5–10 wt.%, Na2O/K2O = 0.5–2, TiO2 <0.7 wt.% and metaluminous character. Systematic modal variation of plagioclase (An11–16 Ab82–88, K-feldspar (Or27–95 Ab5–61, diopside (En34–40Fs11–18Wo46–49, biotite, and Ca-amphibole (edenite build up three syenite facies within it and imply the role of in-situ fractional crystallization (FC. Evidences such as (1 disequilibrium micro-textures in feldspars, (2 microgranular mafic enclaves (MME and (3 synplutonic dykes signify mixing of shoshonitic mafic magma (MgO = 4–5 wt.%, SiO2 = 54–59 wt.%, K2O/Na2O = 0.4–0.9 with syenite. Molecular-scale mixing of mafic magma resulted disequilibrium growth of feldspars in syenite. Physical entity of mafic magma preserved as MME due to high thermal-rheological contrast with syenite magma show various hybridization through chemical exchange, mechanical dilution enhanced by chaotic advection and phenocryst migration. In synplutonic dykes, disaggregation and mixing of mafic magma was confined within the conduit of injection. Major-oxides mass balance test quantified that approximately 0.6 portions of mafic magma had interacted with most evolved syenite magma and generated most hybridized MME and dyke samples. It is unique that all the rock types (syenite, MME and synplutonic dykes share similar shoshonitic and metaluminous character; mineral chemistry, REE content, coherent geochemical variation in Harker diagram suggest that mixing of magma between similar composition. Outcrop-scale features of crystal accumulation and flow fabrics also significant along with MME and synplutonic dykes in syenite suggesting that Yelagiri syenite magma chamber had evolved

  6. SEM-MLA-based Investigation of the Composition of Mafic Volcaniclastic Deposits from the Paraná Large Igneous Province, Brazil

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    Höfig, D. F.; Höfig, T. W.; Licht, O. A. B.; Haser, S.; Valore, L.

    2017-12-01

    Mafic volcaniclastic deposits (MVDs) have been widely reported in Large Igneous Provinces around the world, except for the Paraná Province (review by Ross et al., 2005: J Volcanol Geotherm Res, 145, pp. 281-314). Recent geochemical classification for this unit highlights, however, the occurrence of such deposits, connected to basic lava flows, mostly those High Ti - High P ones (Licht.: J Volcanol Geotherm Res, in press). In southern Brazil, MVDs intercalated with lava flows have been reported at 680 sites, showing conspicuous poorly sorted polymictic breccia at the base, grading to tuff breccias and red silicified tuffs at the top. Newly sampled rocks of Paraná mafic volcanoclastic deposits unravel important information about the composition utilizing Scanning Electron Microscopy-based Mineral Liberation Analysis. Overall, they show similar mineralogy presenting obsidian (25-40%), different phases of iron oxide (5-20%), quartz (10-25%), plagioclase (5-25%), celadonite (5-25%), and chlorite (5-10%). The breccias reveal a greater content of celadonite due to the presence of altered hypohyaline and hypocrystalline basaltic shards, whereas the tuffs are more enriched in glass. Different generations of plagioclase are attributed to various basalt shards and clasts as well vitroclasts found in the matrix. It is proposed that the MVDs were generated by explosive events due the interaction between the ascending mafic magma and deep aquifer systems and its siliciclastic matrix represents the country rock, i.e., the underneath Paleozoic sedimentary sequence of Paraná Basin.

  7. The Magma Chamber Simulator: Modeling the Impact of Wall Rock Composition on Mafic Magmas during Assimilation-Fractional Crystallization

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    Creamer, J. B.; Spera, F. J.; Bohrson, W. A.; Ghiorso, M. S.

    2012-12-01

    Although stoichiometric titration is often used to model the process of concurrent Assimilation and Fractional Crystallization (AFC) within a compositionally evolving magma body, a more complete treatment of the problem involves simultaneous and self-consistent determination of stable phase relationships and separately evolving temperatures of both Magma (M) and Wall Rock (WR) that interact as a composite M-WR system. Here we present results of M-WR systems undergoing AFC forward modeled with the Magma Chamber Simulator (MCS), which uses the phase modeling capabilities of MELTS (Ghiorso & Sack 1995) as the thermodynamic basis. Simulations begin with one of a variety of mafic magmas (e.g. HAB, MORB, AOB) intruding a set mass of Wall Rock (e.g. lherzolite, gabbro, diorite, granite, metapelite), and heat is exchanged as the M-WR system proceeds towards thermal equilibrium. Depending on initial conditions, the early part of the evolution can involve closed system FC while the WR heats up. The WR behaves as a closed system until it is heated beyond the solidus to critical limit for melt fraction extraction (fc), ranging between 0.08 and 0.12 depending on WR characteristics including composition and, rheology and stress field. Once fc is exceeded, a portion of the anatectic liquid is assimilated into the Magma. The MCS simultaneously calculates mass and composition of the mineral assemblage (Magma cumulates and WR residue) and melt (anatectic and Magma) at each T along the equilibration trajectory. Sensible and latent heat lost or gained plus mass gained by the Magma are accounted for by the MCS via governing Energy Constrained- Recharge Assimilation Fractional Crystallization (EC-RAFC) equations. In a comparison of two representative MCS results, consider a granitic WR intruded by HAB melt (51 wt. % SiO2) at liquidus T in shallow crust (0.1 GPa) with a WR/M ratio of 1.25, fc of 0.1 and a QFM oxygen buffer. In the first example, the WR begins at a temperature of 100o

  8. Reconstruction of multiple P-T-t stages from retrogressed mafic rocks: Subduction versus collision in the Southern Brasília orogen (SE Brazil)

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    Tedeschi, Mahyra; Lanari, Pierre; Rubatto, Daniela; Pedrosa-Soares, Antônio; Hermann, Jörg; Dussin, Ivo; Pinheiro, Marco Aurélio P.; Bouvier, Anne-Sophie; Baumgartner, Lukas

    2017-12-01

    The identification of markers of subduction zones in orogenic belts requires the estimation of paleo-geothermal gradients through pressure-temperature-time (P-T-t) estimates in mafic rocks that potentially derive from former oceanic units once. However, such markers are rare in supracrustal sequences specially in deeply eroded and weathered Precambrian orogens, and reconstructing their metamorphic history is challenging because they are commonly retrogressed and only preserve a few mineral relicts of high-pressure metamorphism. Metamorphosed mafic rocks from Pouso Alegre region of the Neoproterozoic Southern Brasília Orogen outcrop as rare lenses within continental gneisses. They have previously been classified as retrograde eclogites, based on the presence of garnet and the characteristic symplectitic texture replacing omphacite. These rocks were interpreted to mark the suture zone between the Paranapanema and São Francisco cratons. To test the possible record of eclogitic conditions in the Pouso Alegre mafic rocks, samples including the surrounding felsic rocks have been investigated using quantitative compositional mapping, forward thermodynamic modeling and in-situ dating of accessory minerals to refine their P-T-t history. In the metamorphosed mafic rocks, the peak pressure assemblage of garnet and omphacite (Jd20, reconstructed composition) formed at 690 ± 35 °C and 13.5 ± 3.0 kbar, whereas local retrogression into symplectite or corona occurred at 595 ± 25 °C and 4.8 ± 1.5 kbar. The two reactions were coupled and thus took place at the same time. A zircon U-Pb age of 603 ± 7 Ma was obtained for metamorphic rims and linked to the retrogression stage. Monazite and metamorphic zircon U-Th-Pb ages for the surrounding rocks are at ca. 630 Ma and linked to peak pressure conditions similar to the one recorded by the mafic rocks. The low maximal pressure of 14 kbar and the high geothermal gradient do not necessarily support subduction process

  9. Peridotites and mafic igneous rocks at the foot of the Galicia Margin: an oceanic or continental lithosphere? A discussion

    Energy Technology Data Exchange (ETDEWEB)

    Korprobst, J.; Chazot, G.

    2016-10-01

    An ultramafic/mafic complex is exposed on the sea floor at the foot of the Galicia Margin (Spain and Portugal). It comprises various types of peridotites and pyroxenites, as well as amphibole-diorites, gabbros, dolerites and basalts. For chronological and structural reasons (gabbros were emplaced within peridotites before the continental break-up) this unit cannot be assigned to the Atlantic oceanic crust. The compilation of all available petrological and geochemical data suggests that peridotites are derived from the sub-continental lithospheric mantle, deeply transformed during Cretaceous rifting. Thus, websterite dykes extracted from the depleted MORB mantle reservoir (DMM), were emplaced early within the lithospheric harzburgites; subsequent boudinage and tectonic dispersion of these dykes in the peridotites, during deformation stages at the beginning of rifting, resulted in the formation of fertile but isotopically depleted lherzolites. Sterile but isotopically enriched websterites, would represent melting residues in the peridotites, after significant partial melting and melt extraction related to the thermal erosion of the lithosphere. The latter melts are probably the source of brown amphibole metasomatic crystallization in some peridotites, as well as of the emplacement of amphibole-diorite dykes. Melts directly extracted from the asthenosphere were emplaced as gabbro within the sub-continental mantle. Mixing these DMM melts together with the enriched melts extracted from the lithosphere, provided the intermediate isotopic melt-compositions - in between the DMM and Oceanic Islands Basalts reservoir - observed for the dolerites and basalts, none of which are characterized by a genuine N-MORB signature. An enriched lithospheric mantle, present prior to rifting of the Galicia margin, is in good agreement with data from the Messejana dyke (Portugal) and more generally, with those of all continental tholeiites of the Central Atlantic Magmatic Province (CAMP

  10. Petrogenesis and geodynamic implications of Ediacaran highly fractionated A-type granitoids in the north Arabian-Nubian Shield (Egypt): Constraints from whole-rock geochemistry and Sr-Nd isotopes

    Science.gov (United States)

    Sami, Mabrouk; Ntaflos, Theodoros; Farahat, Esam S.; Mohamed, Haroun A.; Hauzenberger, Christoph; Ahmed, Awaad F.

    2018-04-01

    Mineral chemistry, whole-rock geochemical and Sr-Nd isotopic data are reported for the Abu-Diab granitoids in the northern Arabian-Nubian Shield (ANS) of Egypt, to investigate their petrogenesis and geodynamic significance. Gabal Abu-Diab constitute a multiphase pluton, consisting largely of two-mica granites (TMGs) enclosing microgranular enclaves and intruded by garnet bearing muscovite granites (GMGs) and muscovite granites (MGs). The granitoids are weakly peraluminous (A/CNK = 1.01-1.12) and show high SiO2 (>72.9 wt%) and alkali (K2O + Na2O = 8.60-9.13) contents. The geochemical features show that they are post-collisional and highly fractionated A-type granitoids. Compared to their host TMGs, the microgranular enclaves are strongly peraluminous (A/CNK = 1.18-1.24) with lower SiO2 and higher abundances of trace elements. The TMGs are depleted in Ba, Nb, P and Ti and are enriched in LREEs relative to HREEs with weakly negative Eu anomalies (Eu/Eu* = 0.45-0.64). In contrast, the GMGs and MGs are extremely depleted in Ba, Sr and Ti and have tetrad-type REE patterns (TE1-3 = 1.1-1.3) with strongly pronounced negative Eu anomalies (Eu/Eu* = 0.03-0.26), similar to rare metals bearing granites. The Ediacaran (585 ± 24 Ma) TMGs, are characterized by restricted and relatively low initial 87Sr/86Sr ratios (0.70337-0.70382) that suggests their derivation from a depleted mantle source, with little contamination from the older continental crust. In contrast, the GMGs and MGs have extremely high 87Rb/86Sr and 87Sr/86Sr ratios that reflect the disturbance of the Rb-Sr isotopic system and may give an indication for magmatic-fluid interaction. However, all the granitoids display positive εNd(t) (4.41-6.57) and depleted mantle model ages TDM2 between 777 and 956 Ma, which indicate their derivation from a Neoproterozoic juvenile magma sources and preclude the occurrence of pre-Neoproterozoic crustal rocks in the ANS. The microgranular enclaves represent globules of hot mafic

  11. Serpentinization and fluid-rock interaction in Jurassic mafic and ultramafic sea-floor: constraints from Ligurian ophiolite sequences

    Science.gov (United States)

    Vogel, Monica; Früh-Green, Gretchen L.; Boschi, Chiara; Schwarzenbach, Esther M.

    2014-05-01

    The Bracco-Levanto ophiolitic complex (Eastern Liguria) represents one of the largest and better-exposed ophiolitic successions in the Northern Apennines. It is considered to be a fragment of heterogeneous Jurassic lithosphere that records tectono-magmatic and alteration histories similar to those documented along the Mid-Atlantic Ridge, such as at the 15°20'N area and the Atlantis Massif at 30°N. Structural and petrological studies on these rocks provide constraints on metamorphic/deformation processes during formation and hydrothermal alteration of the Jurassic oceanic lithosphere. We present a petrological and geochemical study of deformation processes and fluid-rock interaction in the Bracco-Levanto ophiolitic complex and compare these to modern oceanic hydrothermal systems, such as the Lost City Hydrothermal Field hosted in ultramafic rocks on the Atlantis Massif. A focus is on investigating mass transfer and fluid flow paths during high and low temperature hydrothermal activity, and on processes leading to hydrothermal carbonate precipitation and the formation of ophicalcites, which are characteristic of the Bracco-Levanto sequences. Major element and mineral compositional data allow us to distinguish a multiphase history of alteration characterized by: (1) widespread SiO2 metasomatism during progressive serpentinization, and (2) multiple phases of veining and carbonate precipitation associated with circulation of seawater and high fluid-rock ratios in the shallow ultramafic-dominated portions of the Jurassic seafloor. We observe regional variations in MgO, SiO2 and Al2O3, suggesting Si-flux towards stratigraphically higher units. In general, the ophicalcites have higher Si, Al and Fe concentrations and lower Mg than the serpentinite basement rocks or serpentinites with minimal carbonate veins. Bulk rock trace element data and Sr isotope ratios indicate seawater reacting with rocks of more mafic composition, then channeled towards stratigraphically higher

  12. Linking precious metal enrichment and halogen cycling in mafic magmatic systems: insights from the Rum layered intrusion, NW Scotland

    Science.gov (United States)

    Kelly, A. P.; O'Driscoll, B.; Clay, P. L.; Burgess, R.

    2017-12-01

    Layered intrusions host the world's largest known concentrations of the platinum-group elements (PGE). Emphasis has been attached to the role of halogen-bearing fluids in concentrating the precious metals, but whether this occurs at the magmatic stage, or via subsequent metasomatism, is actively debated. One obstacle to progress has been the analytical difficulty of measuring low abundances of the halogens in the cumulate products of layered intrusions. To elucidate the importance of the halogens in facilitating PGE-mineralisation, as well as fingerprint halogen provenance and assess the importance of halogen cycling in mafic magma systems more generally, a suite of samples encompassing different stages of activity of the Palaeogene Rum layered intrusion was investigated. Halogen abundances were measured by neutron irradiation noble gas mass spectrometric analysis, permitting the detection of relatively low (ppm-ppb) abundances of Cl, Br and I in mg-sized samples. The samples include PGE-enriched chromite seams, various cumulates (e.g., peridotites), picrites (approximating the Rum parental magma), and pegmatites representing volatile-rich melts that circulated the intrusion at a late-stage in its solidification history. The new data reveal that PGE-bearing chromite seams contain relatively low Cl concentrations (2-3 ppm), with high molar ratios of Br/Cl and I/Cl (0.005 and 0.009, respectively). The picrites and cumulates have Br/Cl and I/Cl ratios close to sub-continental lithospheric mantle values of approximately 0.0013 and 0.00002, respectively, and thus likely reflect the Rum magma source region. A positive correlation between Cl and Br signifies comparable partitioning behaviour in all samples. However, I is more variable, displaying a positive correlation with Cl for more primitive samples (e.g. picrite and peridotite), and seemingly decoupling from Br and Cl in chromite seams and pegmatites. The relative enrichment of I over Cl in the chromite seams points

  13. The structure of the Okavango giant mafic dyke swarm in the Karoo magmatic province of North Botswana

    Science.gov (United States)

    Le Gall, B.; Tshoso, G.; Tiercelin, J. J.; Dyment, J.; Aubourg, C.; Feraud, G.; Jourdan, F.; Bertrand, H.

    2003-04-01

    Field structural measurements combined to magnetic dataset (including both aero- and ground magnetic records) allow a systematic investigation of the structure of the Okavango giant (2000 x 100 km) mafic dyke swarm in N Botswana. The results are discussed about a 55 km-long projected section lying perpendicular to the densest zone of the swarm and cutting through Proterozoic granito-gneissic host-rocks. A total dyke population of 423 (magnetic records) or 171 (field data) individual intrusions is identified and consists principally of basalts and dolerites. New high-precision dating (Jourdan et al., this congress) demonstrates the composite nature of the Okavango swarm that includes Karoo dykes (70%) and additional (30%) Proterozoic intrusions. The two dyke populations lie with a similar strike and show no discriminant petro-structural features in the field. These new results make it difficult 1) discriminating Karoo versus Proterozoic dyke groups within the total population derived from magnetics, and 2) defining their respective structural characteristics. About the Karoo dyke population (360 intrusions), field structural observations help to constrain the statistical analysis of some of its geometrical parameters, such as the strike (N110°E), dip (vertical), lenght (ca. 5 km), thickness (18-20 m), spacing, or direction of dyke opening. The dyke-induced crustal dilatation is estimated to 6-10% across the 55 km-long reference section. Structural observations also emphazise the control exerted by preexisting basement fabrics (brittle joints and dykes) on Karoo dyke emplacement. Synmagmatic deformation is restricted to wall-parallel tensile joint networks with no evidence for extensional faulting. The Karoo part of the Okavango giant dyke swam is inferred to have been emplaced under an unidirectional extensional stress field (N70°E). Furthermore, analyzing the anisotropy of magnetic susceptibility of a number of dykes (Tshoso et al., this congress) indicates an

  14. Petrographic, geochemical and isotopic evidence of crustal assimilation processes in the Ponte Nova alkaline mafic-ultramafic massif, SE Brazil

    Science.gov (United States)

    Azzone, Rogério Guitarrari; Montecinos Munoz, Patricio; Enrich, Gaston Eduardo Rojas; Alves, Adriana; Ruberti, Excelso; Gomes, Celsode Barros

    2016-09-01

    Crustal assimilation plus crystal fractionation processes of different basanite magma batches control the evolution of the Ponte Nova cretaceous alkaline mafic-ultramafic massif in SE Brazil. This massif is composed of several intrusions, the main ones with a cumulate character. Disequilibrium features in the early-crystallized phases (e.g., corrosion and sieve textures in cores of clinopyroxene crystals, spongy-cellular-textured plagioclase crystals, gulf corrosion texture in olivine crystals) and classical hybridization textures (e.g., blade biotite and acicular apatite crystals) provide strong evidence of open-system behavior. All samples are olivine- and nepheline-normative rocks with basic-ultrabasic and potassic characters and variable incompatible element enrichments. The wide ranges of whole-rock 87Sr/86Sri and 143Nd/144Ndi ratios (0.70432-0.70641 and 0.512216-0.512555, respectively) are indicative of crustal contribution from the Precambrian basement host rocks. Plagioclase and apatite 87Sr/86Sr ratios (0.70422-0.70927) obtained for the most primitive samples of each intrusion indicate disequilibrium conditions from early- to principal-crystallization stages. Isotope mixing-model curves between the least contaminated alkaline basic magma and heterogeneous local crustal components indicate that each intrusion of the massif is differentiated from the others by varied degrees of crustal contribution. The primary mechanisms of crustal contribution to the Ponte Nova massif involve the assimilation of host rock xenoliths during the development of the chamber environment and the assimilation of partial melts from the surrounding host rocks. Thermodynamic models using the melts algorithm indicate that parental alkaline basic magmas can be strongly affected by contamination processes subsequently to their initial stages of crystallization when there is sufficient energy to assimilate partial melts of crustal host rocks. The assimilation processes are considered to

  15. Genesis of the Permian Kemozibayi sulfide-bearing mafic-ultramafic intrusion in Altay, NW China: Evidence from zircon geochronology, Hf and O isotopes and mineral chemistry

    Science.gov (United States)

    Tang, Dongmei; Qin, Kezhang; Xue, Shengchao; Mao, Yajing; Evans, Noreen J.; Niu, Yanjie; Chen, Junlu

    2017-11-01

    The recently discovered Kemozibayi mafic-ultramafic intrusion and its associated magmatic Cu-Ni sulfide deposits are located at the southern margin of the Chinese Altai Mountain, Central Asian Orogenic Belt in north Xinjiang, NW China. The intrusion is composed of olivine websterite, norite, gabbro and diorite. Disseminated and net-textured Ni-Cu sulfide ores are hosted in the center of the gabbro. In this work, new zircon U-Pb ages, Hf-O isotopic and sulfide S isotopic data, and whole rock and mineral chemical analyses are combined in order to elucidate the characteristics of the mantle source, nature of subduction processes, degree of crustal contamination, geodynamic setting of bimodal magmatism in the region, and the metallogenic potential of economic Cu-Ni sulfide deposit at depth. SIMS zircon U-Pb dating of the gabbro yields Permian ages (278.3 ± 1.9 Ma), coeval with the Kalatongke Cu-Ni deposit and with Cu-Ni deposits in the Eastern Tianshan and Beishan areas. Several lines of evidence (positive εHf(t) from + 7.1 to + 13.3, Al2O3, TiO2 and SiO2 contents in clinopyroxene from olivine websterite, high whole rock TiO2 contents) suggest that the primary magma of the Kemozibayi intrusion was a calc-alkaline basaltic magma derived from depleted mantle, and that the degree of partial melting in the magma source was high. The evolution of the Kemozibayi mafic-ultramafic complex was strongly controlled by fractional crystallization and the crystallization sequence was olivine websterite, norite, and then gabbro. This is evidenced by whole rock Fe2O3 contents that are positively correlated with MgO and negatively correlated with Al2O3, CaO and Na2O, similar LREE enrichment and negative Nb, Ta, Hf anomalies in chondrite and primitive mantle-normalized patterns, and a decrease in total REE and trace elements contents and magnetite content from gabbro through to norite and olivine websterite. Varied and low εHf(t) (+ 7.1 to + 13.3) and high δ18O values (+ 6.4‰ to

  16. Contamination in mafic mineral-rich calc-alkaline granites: a geochemical and Sr-Nd isotope study of the Neoproterozoic Piedade Granite, SE Brazil

    Directory of Open Access Journals (Sweden)

    Leite Renato J.

    2006-01-01

    Full Text Available The Piedade Granite (~600 Ma was emplaced shortly after the main phase of granite magmatism in the Agudos Grandes batholith, Apiaí-Guaxupé Terrane, SE Brazil. Its main units are: mafic mineral-rich porphyritic granites forming the border (peraluminous muscovite-biotite granodiorite-monzogranite MBmg unit and core (metaluminous titanite-bearing biotite monzogranite BmgT unit and felsic pink inequigranular granite (Bmg unit between them. Bmg has high LaN/YbN (up to 100, Th/U (>10 and low Rb, Nb and Ta, and can be a crustal melt derived from deep-seated sources with residual garnet and biotite. The core BmgT unit derived from oxidized magmas with high Mg# (~45, Ba and Sr, fractionated REE patterns (LaN/YbN= 45, 87Sr/86Sr(t~ 0.710, epsilonNd(t ~ -12 to -14, interpreted as being high-K calc-alkaline magmas contaminated with metasedimentary rocks that had upper-crust signature (high U, Cs, Ta. The mafic-rich peraluminous granites show a more evolved isotope signature (87Sr/86Sr(t = 0.713-0.714; epsilonNd(t= -14 to -16, similar to Bmg, and Mg# and incompatible trace-element concentrations intermediate between Bmg and BmgT. A model is presented in whichMBmgis envisaged as the product of contamination between a mafic mineral-rich magma consanguineous with BmgT and pure crustal melts akin to Bmg.

  17. Ar-Ar dating and petrogenesis of the Early Miocene Taşkapı-Mecitli (Erciş-Van) granitoid, Eastern Anatolia Collisional Zone, Turkey

    Science.gov (United States)

    Oyan, Vural

    2018-06-01

    The Early Miocene Taşkapı-Mecitli granitoid that is located in the northern section of the Eastern Anatolia Collision Zone has typical I-type, metaluminous and calk-alkaline characteristics. It also contains mafic microgranular / magmatic enclaves (MMEs). New Ar-Ar dating results show that the age of the Taşkapı-Mecitli granitoid is ∼23 Ma and it crystallised in the Early Miocene, in contrast to its previously known Cretaceous age. Identical crystallisation ages (∼23 Ma), similar mineral assemblages and geochemical compositions, and indistinguishable isotopic compositions of MMEs and host rocks imply that the MMEs are most consistent with a cumulate origin formed at earlier stages of the same magmatic system that produced the Taşkapı-Mecitli granitoid. MELTS modelling suggests that magma of the Taşkapı-Mecitli granitoid was the result of fractionation under a crustal pressure of 4 kbar, with a H2O content of 1.5%. EC-AFC model calculation reveals that the Taşkapı-Mecitli granitoid includes from 0.5% to 2% crustal assimilation rates. These rates indicate that crustal contamination can be negligible when compared to fractional crystallisation in the evolution of the magma beneath the Taşkapı-Mecitli granitoid. The partial melting model calculations and MORB-normalised trace element concentrations of the least evolved samples of the Taşkapı-Mecitli granitoid are consistent with those of mafic melts obtained from partial melting of interacting mantle- lower crust with a melting degree of 18%. The age (23 Ma) of the post- or syn-collisional Taşkapı-Mecitli granitoid suggests that the collision between Arabian and Eurasian plates could be before/around ∼23 Ma (Late Oligocene to Early Miocene).

  18. The chemical and isotopic differentiation of an epizonal magma body: Organ Needle pluton, New Mexico

    Science.gov (United States)

    Verplanck, P.L.; Farmer, G.L.; McCurry, M.; Mertzman, S.A.

    1999-01-01

    Major and trace element, and Nd and Sr isotopic compositions of whole rocks and mineral separates from the Oligocene, alkaline Organ Needle pluton (ONP), southern New Mexico, constrain models for the differentiation of the magma body parental to this compositionally zoned and layered epizonal intrusive body. The data reveal that the pluton is rimmed by lower ??(Nd) (~-5) and higher 87Sr/86Sr (~0.7085) syenitic rocks than those in its interior (??(Nd) ~ 2, 87Sr/86Sr ~0.7060) and that the bulk compositions of the marginal rocks become more felsic with decreasing structural depth. At the deepest exposed levels of the pluton, the ??(Nd)~-5 lithology is a compositionally heterogeneous inequigranular syenite. Modal, compositional and isotopic data from separates of rare earth element (REE)-bearing major and accesory mineral phases (hornblende, titanite, apatite, zircon) demonstrate that this decoupling of trace and major elements in the inequigranular syenite results from accumulation of light REE (LREE)-bearing minerals that were evidently separated from silicic magmas as the latter rose along the sides of the magma chamber. Chemical and isotopic data for microgranular mafic enclaves, as well as for restite xenoliths of Precambrian granite wall rock, indicate that the isotopic distinction between the marginal and interior facies of the ONP probably reflects assimilation of the wall rock by ??(Nd) ~-2 mafic magmas near the base of the magma system. Fractional crystallization and crystal liquid separation of the crystally contaminated magma at the base and along the margins of the chamber generated the highly silicic magmas that ultimately pooled at the chamber top.

  19. Field geology, geochronology and geochemistry of mafic-ultramafic rocks from Alxa, China: Implications for Late Permian accretionary tectonics in the southern Altaids

    Science.gov (United States)

    Feng, Jianyun; Xiao, Wenjiao; Windley, Brian; Han, Chunming; Wan, Bo; Zhang, Ji'en; Ao, Songjian; Zhang, Zhiyong; Lin, Lina

    2013-12-01

    The time of termination of orogenesis for the southern Altaids has been controversial. Systematic investigations of field geology, geochronology and geochemistry on newly discriminated mafic-ultramafic rocks from northern Alxa in the southern Altaids were conducted to address the termination problem. The mafic-ultramafic rocks are located in the Bijiertai, Honggueryulin, and Qinggele areas, stretching from west to east for about 100 km. All rocks occur high-grade gneisses as tectonic lenses that are composed of peridotite, pyroxenite, gabbro, and serpentinite, most of which have undergone pronounced alteration, i.e., serpentinization and chloritization. Geochemically, the rocks are characterized by uniform compositional trends, i.e., with low SiO2-contents (42.51-52.21 wt.%) and alkalinity (Na2O + K2O) (0.01-5.45 wt.%, mostly less than 0.8 wt.%), and enrichments in MgO (7.37-43.36 wt.%), with Mg# = 52.75-91.87. As the rocks have been strongly altered and have a wide range of loss-on-ignition (LOI: 0.44-14.07 wt.%) values, they may have been subjected to considerable alteration by either seawater or metamorphic fluids. The REE and trace element patterns show a relatively fractionated trend with LILE enrichment and HFSE depletion, similar to that of T-MORB between N-MORB and E-MORB, indicating that the parental melt resulted from the partial melting of oceanic lithospheric mantle overprinted by fluid alteration of island-arc origin. The ultramafic rocks are relics derived from the magma after a large degree of partial melting of oceanic lithospheric mantle with superposed island arc processes under the influence of mid-ocean-ridge magmatism. LA-ICP MS U-Pb zircon ages of gabbros from three spots are 274 ± 3 Ma (MSWD = 0.35), 306 ± 3 Ma (MSWD = 0.49), 262 ± 5 Ma (MSWD = 1.2), respectively, representing the formation ages of the mafic-ultramafic rocks. Therefore, considering other previously published data, we suggest that the mafic-ultramafic rocks were products of

  20. A high-pyrite semianthracite of Late Permian age in the Songzao Coalfield, southwestern China: Mineralogical and geochemical relations with underlying mafic tuffs

    Science.gov (United States)

    Dai, S.; Wang, X.; Chen, W.; Li, D.; Chou, C.-L.; Zhou, Y.; Zhu, Chen; Li, H.; Zhu, Xudong; Xing, Y.; Zhang, W.; Zou, J.

    2010-01-01

    The No. 12 Coal (Late Permian) in the Songzao Coalfield, Chongqing, southwestern China, is characteristically high in pyrite and some trace elements. It is uniquely deposited directly above mafic tuff beds. Samples of coal and tuffs have been studied for their mineralogy and geochemistry using inductively coupled plasma-mass spectrometry, X-ray fluorescence, plasma low-temperature ashing plus powder X-ray diffraction, and scanning electron microscopy equipped with energy-dispersive X-ray analysis.The results show that the minerals of the No. 12 Coal are mainly composed of pyrite, clay minerals (kaolinite, chamosite, and illite), ankerite, calcite, and trace amounts of quartz and boehmite. Kaolinite and boehmite were mainly derived from sediment source region of mafic tuffs. Chamosite was formed by the reaction of kaolinite with Fe-Mg-rich fluids during early diagenesis. The high pyrite (Sp,d=8.83%) in the coal was related to marine transgression over peat deposits and abundant Fe derived from the underlying mafic tuff bed. Ankerite and calcite were precipitated from epigenetic fluids.Chemical compositions of incompatible elements indicate that the tuffs were derived from enriched mantle and the source magmas had an alkali-basalt character. Compared to other coals from the Songzao Coalfield and common Chinese coals, the No. 12 Coal has a lower SiO2/Al2O3 (1.13) but a higher Al2O3/Na2O (80.1) value and is significantly enriched in trace elements including Sc (13.5??g/g), V (121??g/g), Cr (33.6??g/g), Co (27.2??g/g), Ni (83.5??g/g), Cu (48.5??g/g), Ga (17.3??g/g), Y (68.3??g/g), Zr (444??g/g), Nb (23.8??g/g), and REE (392??g/g on average). Above mineralogical compositions, as well as similar ratios of selected elements (e.g., SiO2/Al2O3 and Al2O3/Na2O) and similar distribution patterns of incompatible elements (e.g., the mantle-normalized diagram for incompatible elements and chondrite-normalized diagram for rare earth elements) of coal and tuff, indicated that

  1. A high-pyrite semianthracite of Late Permian age in the Songzao Coalfield, southwestern China: Mineralogical and geochemical relations with underlying mafic tuffs

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Shifeng; Wang, Xibo; Chen, Wenmei [State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Beijing 100083, (China); Li, Dahua [Research Center of State Key Laboratory of Coal Resources and Safe Mining, Chongqing 400042, (China); Chou, Chen-Lin [Illinois State Geological Survey (Emeritus), 615 East Peabody Drive, Champaign, IL 61820, (United States); Zhou, Yiping [Yunnan Institute of Coal Geology Prospection, Kunming 650218, (China); Zhu, Changsheng; Li, Hang [Research Center of State Key Laboratory of Coal Resources and Safe Mining, Chongqing 400042, (China); Zhu, Xingwei; Xing, Yunwei; Zhang, Weiguo; Zou, Jianhua [State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Beijing 100083, (China)

    2010-09-01

    The No. 12 Coal (Late Permian) in the Songzao Coalfield, Chongqing, southwestern China, is characteristically high in pyrite and some trace elements. It is uniquely deposited directly above mafic tuff beds. Samples of coal and tuffs have been studied for their mineralogy and geochemistry using inductively coupled plasma-mass spectrometry, X-ray fluorescence, plasma low-temperature ashing plus powder X-ray diffraction, and scanning electron microscopy equipped with energy-dispersive X-ray analysis. The results show that the minerals of the No. 12 Coal are mainly composed of pyrite, clay minerals (kaolinite, chamosite, and illite), ankerite, calcite, and trace amounts of quartz and boehmite. Kaolinite and boehmite were mainly derived from sediment source region of mafic tuffs. Chamosite was formed by the reaction of kaolinite with Fe-Mg-rich fluids during early diagenesis. The high pyrite (S{sub p,d} 8.83%) in the coal was related to marine transgression over peat deposits and abundant Fe derived from the underlying mafic tuff bed. Ankerite and calcite were precipitated from epigenetic fluids. Chemical compositions of incompatible elements indicate that the tuffs were derived from enriched mantle and the source magmas had an alkali-basalt character. Compared to other coals from the Songzao Coalfield and common Chinese coals, the No. 12 Coal has a lower SiO{sub 2}/Al{sub 2}O{sub 3} (1.13) but a higher Al{sub 2}O{sub 3}/Na{sub 2}O (80.1) value and is significantly enriched in trace elements including Sc (13.5 {mu}g/g), V (121 {mu}g/g), Cr (33.6 {mu}g/g), Co (27.2 {mu}g/g), Ni (83.5 {mu}g/g), Cu (48.5 {mu}g/g), Ga (17.3 {mu}g/g), Y (68.3 {mu}g/g), Zr (444 {mu}g/g), Nb (23.8 {mu}g/g), and REE (392 {mu}g/g on average). Above mineralogical compositions, as well as similar ratios of selected elements (e.g., SiO{sub 2}/Al{sub 2}O{sub 3} and Al{sub 2}O{sub 3}/Na{sub 2}O) and similar distribution patterns of incompatible elements (e.g., the mantle-normalized diagram for

  2. Inventario de Hymenoptera (Hexapoda en El Ventorrillo: un rico enclave de biodiversidad en la Sierra de Guadarrama (España Central

    Directory of Open Access Journals (Sweden)

    Nieves-Aldrey, José Luis

    2003-12-01

    Sierra de Guadarrama. Toda la zona está, sin embargo, bajo la potencial amenaza de impacto ambiental por la creciente presión humana y urbanística de la cercana urbe de Madrid. Se insta a los responsables de la conservación del Medio Ambiente en la Comunidad de Madrid a tomar medidas para garantizar la protección de este singular enclave de biodiversidad, y de su entorno, en la sierra madrileña. En este sentido, esperamos que este trabajo contribuya a apoyar la reciente propuesta de creación del Parque Nacional de la Sierra de Guadarrama.

  3. A major 2.1 Ga event of mafic magmatism in west Africa: An Early stage of crustal accretion

    Science.gov (United States)

    Abouchami, Wafa; Boher, Muriel; Michard, Annie; Albarede, Francis

    1990-10-01

    Birimian terranes from West Africa (Mauritania, Senegal, Ivory Coast, Burkina Faso, Niger) comprise two major units: a dominantly mafic bimodal volcanic unit and a volcano-detrital unit with mostly felsic to intermediate protolith. Stratigraphic relationships of these units are still a matter of debate but current work suggest that they both formed in a short time interval around 2.1 Ga. Widespread basaltic magmas from the bimodal unit have been analyzed for REE distributions and Sr-Nd isotopes. Three Sm-Nd isochrons on tholeiitic lavas were obtained at 2.229±0.042 Ga and initial ɛNd = 3.6±1.0 for Mauritania, 2.126±0.024 Ga and initial ɛNd = 2.9±0.7 for Burkina Faso, 2.063±0.041 Ga and initial ɛNd = 3.1± .0 for Eastern Senegal, data which compare with the age of 2.11±0.09 Ga and initial ɛNd = 2.1±1.8 obtained in Guyana by Gruau et al. (1985). Samples from other localities (Ivory Coast, Niger) give generally similar results. Although the variations of Sm/Nd ratios and the scatter of ɛNd(T) values from +1.2 to +4.3 preclude a single origin for these magmas, initial isotopic heterogeneities are unlikely to bias significantly the ages given by the isochrons which are in good agreement with U-Pb zircon ages (Boher et al., 1989; unpublished data, 1990). Presence of lavas with frequent pillow structures and sediments virtually free of older recycled components suggests that Birimian terranes formed in ocean basins far from continental influence. The isotopic heterogeneities are not consistent with a MORB-like mantle source. Most lavas are slightly depleted in LREE and inversion of the data through a melting model suggests 5-15 percent melting of a slightly depleted Iherzolite. Strong depletion (Burkina Faso) and slight enrichment (Senegal) are occasionally observed. With a noticeable trend of Ti enrichment with differentiation intermediate between that of MORB and IAT, the geochemical signature of Birimian basalts does not fit the best known geodynamic

  4. Integrated Experimental and Modeling Studies of Mineral Carbonation as a Mechanism for Permanent Carbon Sequestration in Mafic/Ultramafic Rocks

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhengrong [Yale Univ., New Haven, CT (United States); Qiu, Lin [Yale Univ., New Haven, CT (United States); Zhang, Shuang [Yale Univ., New Haven, CT (United States); Bolton, Edward [Yale Univ., New Haven, CT (United States); Bercovici, David [Yale Univ., New Haven, CT (United States); Ague, Jay [Yale Univ., New Haven, CT (United States); Karato, Shun-Ichiro [Yale Univ., New Haven, CT (United States); Oristaglio, Michael [Yale Univ., New Haven, CT (United States); Zhu, Wen-Iu [Univ. of Maryland, College Park, MD (United States); Lisabeth, Harry [Univ. of Maryland, College Park, MD (United States); Johnson, Kevin [Univ. of Hawaii, Honolulu, HI (United States)

    2014-09-30

    A program of laboratory experiments, modeling and fieldwork was carried out at Yale University, University of Maryland, and University of Hawai‘i, under a DOE Award (DE-FE0004375) to study mineral carbonation as a practical method of geologic carbon sequestration. Mineral carbonation, also called carbon mineralization, is the conversion of (fluid) carbon dioxide into (solid) carbonate minerals in rocks, by way of naturally occurring chemical reactions. Mafic and ultramafic rocks, such as volcanic basalt, are natural candidates for carbonation, because the magnesium and iron silicate minerals in these rocks react with brines of dissolved carbon dioxide to form carbonate minerals. By trapping carbon dioxide (CO2) underground as a constituent of solid rock, carbonation of natural basalt formations would be a secure method of sequestering CO2 captured at power plants in efforts to mitigate climate change. Geochemical laboratory experiments at Yale, carried out in a batch reactor at 200°C and 150 bar (15 MPa), studied carbonation of the olivine mineral forsterite (Mg2SiO4) reacting with CO2 brines in the form of sodium bicarbonate (NaHCO3) solutions. The main carbonation product in these reactions is the carbonate mineral magnesite (MgCO3). A series of 32 runs varied the reaction time, the reactive surface area of olivine grains and powders, the concentration of the reacting fluid, and the starting ratio of fluid to olivine mass. These experiments were the first to study the rate of olivine carbonation under passive conditions approaching equilibrium. The results show that, in a simple batch reaction, olivine carbonation is fastest during the first 24 hours and then slows significantly and even reverses. A natural measure of the extent of carbonation is a quantity called the carbonation fraction, which compares the amount of carbon removed from solution, during a run, to the maximum amount

  5. Ferroan Dolomitization by Seawater Interaction with Mafic Igneous Dikes and Carbonate Host Rock at the Latemar Platform, Dolomites, Italy: Numerical Modeling of Spatial, Temporal, and Temperature Data

    Directory of Open Access Journals (Sweden)

    K. Blomme

    2017-01-01

    Full Text Available Numerous publications address the petrogenesis of the partially dolomitized Latemar carbonate platform, Italy. A common factor is interpretation of geochemical data in terms of heating via regional igneous activity that provided kinetically favorable conditions for replacement dolomitization. New field, petrographic, XRD, and geochemical data demonstrate a spatial, temporal, and geochemical link between replacement dolomite and local mafic igneous dikes that pervasively intrude the platform. Dikes are dominated by strongly altered plagioclase and clinopyroxene. Significantly, where ferroan dolomite is present, it borders dikes. We hypothesize that seawater interacted with mafic minerals, causing Fe enrichment in the fluid that subsequently participated in dolomitization. This hypothesis was tested numerically through thermodynamic (MELTS, Arxim-GEM and reactive flow (Arxim-LMA simulations. Results confirm that seawater becomes Fe-enriched during interaction with clinopyroxene (diopside-hedenbergite and plagioclase (anorthite-albite-orthoclase solid solutions. Reaction of modified seawater with limestone causes ferroan and nonferroan replacement dolomitization. Dolomite quantities are strongly influenced by temperature. At 40 to 80°C, ferroan dolomite proportions decrease with increasing temperature, indicating that Latemar dolomitization likely occurred at lower temperatures. This relationship between igneous dikes and dolomitization may have general significance due to the widespread association of carbonates with rifting-related igneous environments.

  6. Textures, trace element compositions, and U-Pb ages of titanite from the Mangling granitoid pluton, East Qinling Orogen: Implications for magma mixing and destruction of the North China Craton

    Science.gov (United States)

    Hu, Hao; Li, Jian-Wei; McFarlane, Christopher R. M.; Luo, Yan; McCarron, Travis

    2017-07-01

    The Mangling granitoid pluton, located along the southern margin of the North China Craton, consists mainly of monzogranite with minor amounts of diorite. The monzogranite contains abundant mafic microgranular enclaves (MMEs) and is intruded by numerous mafic dikes, providing an opportunity to study magma mixing and its role in the formation of the granitioid pluton. In this paper, we present in situ analysis of U-Pb isotopes and trace element compositions of titanite from the MMEs and the host monzogranite using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry to document the role of magma mixing in the formation of the Mangling granitoid pluton. Titanite grains from the MMEs (type 1) are euhedral with patchy zoning, whereas the varieties from the closely associated host monzogranite are euhedral and consist of two types (type 2 and type 3). Type 2 titanite is more abundant and has oscillatory zoning without Fe-Ti oxide inclusions, whereas type 3 grains commonly have Fe-Ti oxide inclusions in the core that is rimmed by inclusion-free overgrowths with weak oscillatory zoning. Titanite from monzogranite without MMEs (type 4) is euhedal and has weak oscillatory zoning, with rare ilmenite inclusions in the core. Titanite from a mafic dike intruding the monzogranite (type 5) is anhedral and has sector zoning. Titanite grains from MMEs and the monzogranite (type 1, 2 and 3) have U-Pb ages that are indistinguishable (149 ± 1 Ma, 148 ± 1 Ma and 148 ± 2 Ma, respectively). These ages agree well with zircon U-Pb ages of 150 ± 1 Ma, 150 ± 1 Ma and 149 ± 1 Ma for the MMEs, host monzogranite, and mafic dike, respectively. The age consistency thus confirms coeval formation of the MMEs, the host monzogranite, and the mafic dikes, demonstrating a mafic magmatic, rather than extraneous or restitic origin for the MMEs. Titanite grains from the MMEs (type 1) and mafic dike (type 5) have much lower Al2O3, REE, Nb/Zr, Y/Zr, and Lu/Hf, but higher (Ce + Nd)/Y and La

  7. Occurrence model for magmatic sulfide-rich nickel-copper-(platinum-group element) deposits related to mafic and ultramafic dike-sill complexes: Chapter I in Mineral deposit models for resource assessment

    Science.gov (United States)

    Schulz, Klaus J.; Woodruff, Laurel G.; Nicholson, Suzanne W.; Seal, Robert R.; Piatak, Nadine M.; Chandler, Val W.; Mars, John L.

    2014-01-01

    Magmatic sulfide deposits containing nickel (Ni) and copper (Cu), with or without (±) platinum-group elements (PGE), account for approximately 60 percent of the world’s nickel production. Most of the remainder of the Ni production is derived from lateritic deposits, which form by weathering of ultramafic rocks in humid tropical conditions. Magmatic Ni-Cu±PGE sulfide deposits are spatially and genetically related to bodies of mafic and/or ultramafic rocks. The sulfide deposits form when the mantle-derived mafic and/or ultramafic magmas become sulfide-saturated and segregate immiscible sulfide liquid, commonly following interaction with continental crustal rocks.

  8. The size-isotopic evolution connection among layered mafic instrusions: Clues from a Sr-Nd isotopic study of a small complex

    Science.gov (United States)

    Poitrasson, Franck; Pin, Christian; Duthou, Jean-Louis; Platevoet, Bernard

    1994-05-01

    Several theoretical and experimental works have focused on the processes occuring in continental mafic magma chambers. In contrast, systematic isotopic studies of natural remnants of these latter remain scarce, although they can give fundamental constraints for theoretical studies. This is especially true if different layered complex with contrasting characteristics (e.g., different size) are compared. For this reason, we present the results of a Sr-Nd isotopic profile across a small layered mafic intrusion of Permian age exposed near Fozzano (SW Corsica). In the main zone of the layered section, decreasing Sr-87/Sr(sub i)-86 and increasing Nd-143/Nd(sub i)-144 are observed from less evolved (bottom) to more evolved (top) rocks. This peculiar pattern precludes assimilation and fractional crystallization (AFC) as a dominant mechanism in the petrogenesis of this body. Instead, we interpret this trend as reflecting the dilution of an early stage contaminated magma by several reinjections of fresh basalt in the chamber. In agreement with mineralogical and structural data, every cyclic unit is interpreted as a new magmatic input. On the basis of rough refill and fractional crystallization (RFC) calculations, the average volume for each reinjection is estimated to have been about 0.04 cu km. The cumulative volume of these injections would amount to about 75% of the total volume of the layered complex. This implies that reinjections were accompanied by an important increase of the volume of the chamber or by magma withdrawal by surface eruptions. The RFC mechanism documented within this small layered body constrasts with the isotopic pattern observed between several intrusions at the regional scale in SW Corsica, and within large continental mafic magma chambers elsewhere. In these cases the isotopic evolution is dominated by AFC processes, and there is no clear isotopic evidence for reinjections, unless major influx of fresh magma occurred. It is suggested that there is

  9. Interactions between mafic eruptions and glacial ice or snow: implications of the 2010 Eyjafjallajökull, Iceland, eruption for hazard assessments in the central Oregon Cascades

    Science.gov (United States)

    McKay, D.; Cashman, K. V.

    2010-12-01

    The 2010 eruption of Eyjafjallajökull, Iceland, demonstrated the importance of addressing hazards specific to mafic eruptions in regions where interactions with glacial ice or snow are likely. One such region is the central Oregon Cascades, where there are hundreds of mafic vents, many of which are Holocene in age. Here we present field observations and quantitative analyses of tephra deposits from recent eruptions at Sand Mountain, Yapoah Cone, and Collier Cone (all advance, which lasted from ~2 to 8 ka in the central Oregon Cascades (Marcott et al., 2009). During the Neoglacial, winter snowfall was likely ~23% greater and summer temperatures ~1.4°C cooler than present (Marcott, 2009). Although ice did not advance to the elevation of the Sand Mountain vents during this time, the eruption could have occurred through several meters of snow. We have also seen very fine-grained tephra at Yapoah Cone, which is located at a higher elevation and may have interacted with glacial ice. In addition to being characterized by unusually fine grainsize, the Yapoah tephra blanket is deposited directly on top of hyaloclastite in several locations. Tephra from Collier Cone is not characterized by unusually fine grainsize, but several sections of the deposit exhibit features that suggest deposition on top of, or interbedding with, snow that later melted away. Identification of features in mafic tephra that suggest interactions with glacial ice or snow has significant implications for regional volcanic hazard assessments. Specifically, the unique hazards posed by Eyjafjallajökull, especially hazards to air travel caused by unusually fine-grained tephra, could be repeated in the Cascades. Although glacial ice is presently limited to elevations above ~2300 m in the central Oregon Cascades, winter snowpack can exceed 5 m at elevations of ~1800 m and above. If a cinder cone eruption were to occur during winter months, interaction with snow could generate phreatomagmatic activity and

  10. 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.

  11. Geodynamic interpretation of the 40Ar/39Ar dating of ophiolitic and arc-related mafics and metamafics of the northern part of the Anadyr-Koryak region

    Science.gov (United States)

    Palandzhyan, S.A.; Layer, P.W.; Patton, W.W.; Khanchuk, A.I.

    2011-01-01

    Isotope datings of amphibole-bearing mafics and metamafics in the northern part of the Anadyr-Koryak region allow clarification of the time of magmatic and metamorphic processes, which are synchronous with certain stages of the geodynamic development of the northwest segment of the Pacific mobile belt in the Phanerozoic. To define the 40Ar/39Ar age of amphiboles, eight samples of amphibole gabbroids and metamafics were selected during field work from five massifs representing ophiolites and mafic plutons of the island arc. Rocks from terranes of three foldbelts: 1) Pekulnei (Chukotka region), 2) Ust-Belaya (West Koryak region), and 3) the Tamvatnei and El'gevayam subterranes of the Mainits terrane (Koryak-Kamchatka region), were studied. The isotope investigations enabled us to divide the studied amphiboles into two groups varying in rock petrographic features. The first was represented by gabbroids of the Svetlorechensk massif of the Pekulnei Range and by ophiolites of the Tamvatnei Mts.; their magmatic amphiboles show the distribution of argon isotopes in the form of clearly distinguished plateau with an age ranging within 120-129 Ma. The second group includes metamorphic amphiboles of metagabbroids and apogabbro amphibolites of the Ust-Belaya Mts., Pekulnei and Kenkeren ranges (El'gevayam subterranes). Their age spectra show loss of argon and do not provide well defined plateaus the datings obtained for them are interpreted as minimum ages. Dates of amphiboles from the metagabbro of the upper tectonic plate of the Ust-Belaya allochthon points to metamorphism in the suprasubduction environment in the fragment of Late Neoproterozoic oceanic lithosphere in Middle-Late Devonian time, long before the Uda-Murgal island arc system was formed. The amphibolite metamorphism in the dunite-clinopyroxenite-metagabbro Pekulnei sequence was dated to occur at the Permian-Triassic boundary. The age of amphiboles from gabbrodiorites of the Kenkeren Range was dated to be Early

  12. Source and Enrichment of Toxic Elements in Coal Seams around Mafic Intrusions: Constraints from Pyrites in the Yuandian Coal Mine in Anhui, Eastern China

    Directory of Open Access Journals (Sweden)

    Yanfei An

    2018-04-01

    Full Text Available Pyrite, a mineral that can cause potential environmental issues in coal mining, is commonly found in coal seams around intrusions. In this paper, pyrites from the Yuandian Coal Mine (Huaibei Coalfield, Anhui, Eastern China were studied using SEM, Raman and LA-ICP-MS. The pyrite morphologic and geochemical data suggest that (1 four pyrite generations are present (framboidal sedimentary pyrites (Py I in the original coal, coarse-grained magmatic pyrites (Py II in the intruding diabase, fine-grained metamorphic pyrites (Py III in the intrusive contact aureole, and spheroid/vein hydrothermal pyrites (Py IV in the cokeite; and (2 concentrations of cobalt, nickel, arsenic, selenium, lead and copper in the metamorphic pyrites are much higher than the other pyrite generations. We propose that mafic magmatism is the main contributor of the toxic elements to the intrusion-related cokeite at Yuandian.

  13. Early Cretaceous high-Ti and low-Ti mafic magmatism in Southeastern Tibet: Insights into magmatic evolution of the Comei Large Igneous Province

    Science.gov (United States)

    Wang, Yaying; Zeng, Lingsen; Asimow, Paul D.; Gao, Li-E.; Ma, Chi; Antoshechkina, Paula M.; Guo, Chunli; Hou, Kejun; Tang, Suohan

    2018-01-01

    The Dala diabase intrusion, at the southeastern margin of the Yardoi gneiss dome, is located within the outcrop area of the 132 Ma Comei Large Igneous Province (LIP), the result of initial activity of the Kerguelen plume. We present new zircon U-Pb geochronology results to show that the Dala diabase was emplaced at 132 Ma and geochemical data (whole-rock element and Sr-Nd isotope ratios, zircon Hf isotopes and Fe-Ti oxide mineral chemistry) to confirm that the Dala diabase intrusion is part of the Comei LIP. The Dala diabase can be divided into a high-Mg/low-Ti series and a low-Mg/high-Ti series. The high-Mg/low-Ti series represents more primitive mafic magma compositions that we demonstrate are parental to the low-Mg/high-Ti series. Fractionation of olivine and clinopyroxene, followed by plagioclase within the low-Mg series, lead to systematic changes in concentrations of mantle compatible elements (Cr, Co, Ni, and V), REEs, HFSEs, and major elements such as Ti and P. Some Dala samples from the low-Mg/high-Ti series contain large ilmenite clusters and show extreme enrichment of Ti with elevated Ti/Y ratios, likely due to settling and accumulation of ilmenite during the magma chamber evolution. However, most samples from throughout the Comei LIP follow the Ti-evolution trend of the typical liquid line of descent (LLD) of primary OIB compositions, showing strong evidence of control of Ti contents by differentiation processes. In many other localities, however, primitive magmas are absent and observed Ti contents of evolved magmas cannot be quantitatively related to source processes. Careful examination of the petrogenetic relationship between co-existing low-Ti and high-Ti mafic rocks is essential to using observed rock chemistry to infer source composition, location, and degree of melting.

  14. A hybrid composite dike suite from the northern Arabian Nubian Shield, southwest Jordan: Implications for magma mixing and partial melting of granite by mafic magma

    Science.gov (United States)

    Jarrar, Ghaleb H.; Yaseen, Najel; Theye, Thomas

    2013-03-01

    The Arabian Nubian Shield is an exemplary juvenile continental crust of Neoproterozoic age (1000-542 Ma). The post-collisional rift-related stage (~ 610 to 542 Ma) of its formation is characterized among others by the intrusion of several generations of simple and composite dikes. This study documents a suite of hybrid composite dikes and a natural example of partial melting of granite by a mafic magma from the northernmost extremity of Arabian Nubian Shield in southwest Jordan. The petrogenesis of this suite is discussed on the basis of field, petrographic, geochemical, and Rb/Sr isotopic data. These dikes give spectacular examples of the interaction between basaltic magma and the granitic basement. This interaction ranges from brecciation, partial melting of the host alkali feldspar granite to complete assimilation of the granitic material. Field structures range from intrusive breccia (angular partially melted granitic fragments in a mafic groundmass) to the formation of hybrid composite dikes that are up to 14 m in thickness. The rims of these dikes are trachyandesite (latite) with alkali feldspar ovoids (up to 1 cm in diameter); while the central cores are trachydacite to dacite and again with alkali feldspar ovoids and xenoliths from the dike rims. The granitic xenoliths in the intrusive breccia have been subjected to at least 33% partial melting. A seven-point Rb/Sr isochron from one of these composite dikes yields an age of 561 ± 33 Ma and an initial 87Sr/86Sr ratio of 0.70326 ± 0.0003 (2σ) and MSWD of 0.62. Geochemical modeling using major, trace, rare earth elements and isotopes suggests the generation of the hybrid composite dike suite through the assimilation of 30% to 60% granitic crustal material by a basaltic magma, while the latter was undergoing fractional crystallization at different levels in the continental crust.

  15. Occurrence and mineral chemistry of chromite and related silicates from the Hongshishan mafic-ultramafic complex, NW China with petrogenetic implications

    Science.gov (United States)

    Ruan, Banxiao; Yu, Yingmin; Lv, Xinbiao; Feng, Jing; Wei, Wei; Wu, Chunming; Wang, Heng

    2017-10-01

    The Hongshishan mafic-ultramafic complex is located in the western Beishan Terrane, NW China, and hosts an economic Ni-Cu deposit. Chromite as accessory mineral from the complex is divided into three types based on its occurrence and morphology. Quantitative electron probe microanalysis (EPMA) have been conducted on the different types of chromites. Type 1 chromite occurs as inclusions within silicate minerals and has relatively homogeneous composition. Type 2 chromite occurs among serpentine, as interstitial phase. Type 3 chromite is zoned and exhibits a sudden change in compositions from core to rim. Type 1 chromite occurs in olivine gabbro and troctolite showing homogeneous composition. This chromite is more likely primary. Interstitial type 2 and zoned type 3 chromite has compositional variation from core to rim and is more likely modified. Abundant inclusions of orthopyroxene, phlogopite and hornblende occur within type 2 and type 3 chromites. The parental melt of type 1 chromite has an estimated composition of 14.5 wt% MgO, 12.3 wt% Al2O3 and 1.9 wt% TiO2 and is characterized by high temperature, picritic affinity, hydrous nature and high Mg and Ti contents. Compositions of chromite and clinopyroxene are distinct from those of Alaskan-type complexes and imply that the subduction-related environment is not reasonable. Post orogenic extension and the early Permian mantle plume are responsible for the emplacement of mafic-ultramafic complexes in the Beishan Terrane. The cores of zoned chromites are classified as ferrous chromite and the rims as ferrian chromite. The formation of ferrian rim involves reaction of ferrous chromite, forsterite and magnetite to produce ferrian chromite and chlorite, or alternaively, the rim can be simply envisioned as the result of external addition of magnetite in solution to the already formed ferrous chromite.

  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. Constraints from geochemistry and oxygen isotopes for the hydrothermal origin of orthoamphibole mafic gneiss in the New Jersey Highlands, north-central Appalachians, USA

    Science.gov (United States)

    Volkert, Richard A.; Peck, William H.

    2017-12-01

    Rare exposures of orthoamphibole mafic (Oam) gneiss of Mesoproterozoic age in the north-central Appalachians are confined to the northwestern New Jersey Highlands where they form thin lens-shaped bodies composed of gedrite and sparse anthophyllite, oligoclase (An13-An20), biotite, magnetite, and local fluorapatite, rutile, and ilmenite. The gneiss is penetratively foliated and has sharp, conformable contacts against enclosing supracrustal paragneiss and marble. Orthoamphibole mafic gneiss is characterized by low SiO2 (48 ± 2.5 wt%), CaO (1.9 ± 1.3 wt%), and high Al2O3 (18 ± 1.2 wt%), Fe2O3 (10.5 ± 1.6 wt%), and MgO (12 ± 2.3 wt%). Trace element abundances overlap those of unaltered amphibolites in the study area and, coupled with δ18O values of 9.45 ± 0.6‰ (VSMOW) from gedrite separates, support an origin from a basalt protolith. The geochemical and isotopic data are consistent with the formation of Oam gneiss through sea floor hydrothermal alteration of basalt at low temperature of 150-200 °C. Mass-balance calculations indicate gains during alteration mainly in MgO and Al2O3 and losses in CaO, Sr, and light rare earth elements. Our results are compatible with the pre-metamorphic alteration of the basalt protoliths through chloritization and plagioclase dissolution that produced a Mg-rich and Ca-poor rock. Subsequent metamorphism of this chlorite-rich rock to the current mineral assemblage of Oam gneiss took place at ca. 1045 Ma, during the Ottawan phase of the Grenvillian Orogeny. The close spatial association in the study area of Oam gneiss bodies and sulfide occurrences suggests an affinity to the style of mineralization associated with volcanogenic massive sulfide (VMS)-type deposits.

  18. Geochemistry and origin of metamorphosed mafic rocks from the Lower Paleozoic Moretown and Cram Hill Formations of North-Central Vermont: Delamination magmatism in the western New England appalachians

    Science.gov (United States)

    Coish, Raymond; Kim, Jonathan; Twelker, Evan; Zolkos, Scott P.; Walsh, Gregory J.

    2015-01-01

    The Moretown Formation, exposed as a north-trending unit that extends from northern Vermont to Connecticut, is located along a critical Appalachian litho-tectonic zone between the paleomargin of Laurentia and accreted oceanic terranes. Remnants of magmatic activity, in part preserved as metamorphosed mafic rocks in the Moretown Formation and the overlying Cram Hill Formation, are a key to further understanding the tectonic history of the northern Appalachians. Field relationships suggest that the metamorphosed mafic rocks might have formed during and after Taconian deformation, which occurred at ca. 470 to 460 Ma. Geochemistry indicates that the sampled metamorphosed mafic rocks were mostly basalts or basaltic andesites. The rocks have moderate TiO2 contents (1–2.5 wt %), are slightly enriched in the light-rare earth elements relative to the heavy rare earths, and have negative Nb-Ta anomalies in MORB-normalized extended rare earth element diagrams. Their chemistry is similar to compositions of basalts from western Pacific extensional basins near volcanic arcs. The metamorphosed mafic rocks of this study are similar in chemistry to both the pre-Silurian Mount Norris Intrusive Suite of northern Vermont, and also to some of Late Silurian rocks within the Lake Memphremagog Intrusive Suite, particularly the Comerford Intrusive Complex of Vermont and New Hampshire. Both suites may be represented among the samples of this study. The geochemistry of all samples indicates that parental magmas were generated in supra-subduction extensional environments during lithospheric delamination.

  19. 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

  20. Multiple magmatism in an evolving suprasubduction zone mantle wedge: The case of the composite mafic-ultramafic complex of Gaositai, North China Craton

    Science.gov (United States)

    Yang, Fan; Santosh, M.; Tsunogae, T.; Tang, Li; Teng, Xueming

    2017-07-01

    The suprasubduction zone mantle wedge of active convergent margins is impregnated by melts and fluids leading to the formation of a variety of magmatic and metasomatic rock suites. Here we investigate a composite mafic-ultramafic intrusion at Gaositai, in the northern margin of the North China Craton (NCC). The hornblende gabbro-serpentinite-dunite-pyroxenite-gabbro-diorite suite surrounded by hornblendites of this complex has long been considered to represent an "Alaskan-type" zoned pluton. We present petrologic, mineral chemical, geochemical and zircon U-Pb and Lu-Hf data from the various rock types from Gaositai including hornblende gabbro, serpentinite, dunite, pyroxenite, diorite and the basement hornblendite which reveal the case of multiple melt generation and melt-peridotite interaction. Our new mineral chemical data from the mafic-ultramafic suite exclude an "Alaskan-type" affinity, and the bulk geochemical features are consistent with subduction-related magmatism with enrichment of LILE (K, Rb, and Ba) and LREE (La and Ce), and depletion of HFSE (Nb, Ta, Zr, and Hf) and HREE. Zircon U-Pb geochronology reveals that the hornblendites surrounding the Gaositai complex are nearly 2 billion years older than the intrusive complex and yield early Paleoproterozoic emplacement ages (2433-2460 Ma), followed by late Paleoproterozoic metamorphism (1897 Ma). The serpentinites trace the history of a long-lived and replenished ancient sub-continental lithospheric mantle with the oldest zircon population dated as 2479 Ma and 1896 Ma, closely corresponding with the ages obtained from the basement rock, followed by Neoproterozoic and Phanerozoic zircon growth. The oldest member in the Gaositai composite intrusion is the dunite that yields emplacement age of 755 Ma, followed by pyroxenite formed through the interaction of slab melt and wedge mantle peridotite at 401 Ma. All the rock suites also carry multiple population of younger zircons ranging in age from Paleozoic to

  1. Orogenic potassic mafic magmatism, a product of alkaline-peraluminous mixing ? Variscan 'calc-alkaline' rocks from the Central Iberian and Ossa Morena Zones, Central Spain.

    Science.gov (United States)

    Scarrow, Jane H.; Cambeses, Aitor; Bea, Fernando; Montero, Pilar; Molina, José F.; Moreno, Juan Antonio

    2013-04-01

    Orogenic magmatic rocks provide information about mantle and crust melt-generation and -interaction processes. In this context, minor potassic mafic stocks which are formed of enriched mantle and crustal components and are common as late-orogenic intrusions in granitic plutons give insight into the timing of new crust formation and crustal recycling. Potassic mafic stocks are prevalent, albeit low volume, constituents of granite batholiths all through the European Variscan (350-280 Ma). In the Central Iberia Zone, Spanish Central System, crustal-melt, S-type, granitoid plutons are intruded by minor concomitant ultramafic-intermediate appinitic-vaugneritic stocks. Notwithstanding their whole-rock calc-alkaline composition, the stocks apparently did not have a subduction-related origin. Recent studies have attributed their genesis to mixing of alkaline mantle and peraluminous crustal melts. Their primary alkaline character, as indicated by amphibole and biotite mineral chemistry data, points, rather, towards an extension-related genesis. In the Ossa Morena Zone, south of the Central Iberian Zone, the igneous rocks also have a whole-rock calc-alkaline composition which has been considered to be the result of northward subduction of the South Portuguese Zone. Nevertheless, identification of a 'sill' of significant volume of mafic magma in the middle crust, the ´IBERSEIS reflective body', in a seismic profile across the Ossa Morena and South Portuguese Zones has cast doubt upon the calc-alkaline magmatism-subduction model; leading, instead, to the magmatism being attributed to intra-orogenic extension related to a mantle plume active from 340 Ma to 330 Ma. The aim here, then, is to reinvestigate the petrogenesis and age of the calc-alkaline rocks of the Ossa Morena Zone to determine their tectonomagmatic context be it subduction-, plume- or extension-related, and establish what they may reveal about mantle-crust interactions. Focussing, initially, on the Valencia del

  2. The behavior of iron and zinc stable isotopes accompanying the subduction of mafic oceanic crust: A case study from Western Alpine ophiolites

    Science.gov (United States)

    Inglis, Edward C.; Debret, Baptiste; Burton, Kevin W.; Millet, Marc-Alban; Pons, Marie-Laure; Dale, Christopher W.; Bouilhol, Pierre; Cooper, Matthew; Nowell, Geoff M.; McCoy-West, Alex J.; Williams, Helen M.

    2017-07-01

    Arc lavas display elevated Fe3+/ΣFe ratios relative to MORB. One mechanism to explain this is the mobilization and transfer of oxidized or oxidizing components from the subducting slab to the mantle wedge. Here we use iron and zinc isotopes, which are fractionated upon complexation by sulfide, chloride, and carbonate ligands, to remark on the chemistry and oxidation state of fluids released during prograde metamorphism of subducted oceanic crust. We present data for metagabbros and metabasalts from the Chenaillet massif, Queyras complex, and the Zermatt-Saas ophiolite (Western European Alps), which have been metamorphosed at typical subduction zone P-T conditions and preserve their prograde metamorphic history. There is no systematic, detectable fractionation of either Fe or Zn isotopes across metamorphic facies, rather the isotope composition of the eclogites overlaps with published data for MORB. The lack of resolvable Fe isotope fractionation with increasing prograde metamorphism likely reflects the mass balance of the system, and in this scenario Fe mobility is not traceable with Fe isotopes. Given that Zn isotopes are fractionated by S-bearing and C-bearing fluids, this suggests that relatively small amounts of Zn are mobilized from the mafic lithologies in within these types of dehydration fluids. Conversely, metagabbros from the Queyras that are in proximity to metasediments display a significant Fe isotope fractionation. The covariation of δ56Fe of these samples with selected fluid mobile elements suggests the infiltration of sediment derived fluids with an isotopically light signature during subduction.

  3. A Low Viscosity Lunar Magma Ocean Forms a Stratified Anorthitic Flotation Crust With Mafic Poor and Rich Units: Lunar Magma Ocean Viscosity

    Energy Technology Data Exchange (ETDEWEB)

    Dygert, Nick [Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin TX USA; Planetary Geosciences Institute, Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, Knoxville TN USA; Lin, Jung-Fu [Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin TX USA; Marshall, Edward W. [Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin TX USA; Kono, Yoshio [HPCAT, Geophysical Laboratory, Carnegie Institution of Washington, Argonne IL USA; Gardner, James E. [Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin TX USA

    2017-11-21

    Much of the lunar crust is monomineralic, comprising >98% plagioclase. The prevailing model argues the crust accumulated as plagioclase floated to the surface of a solidifying lunar magma ocean (LMO). Whether >98% pure anorthosites can form in a flotation scenario is debated. An important determinant of the efficiency of plagioclase fractionation is the viscosity of the LMO liquid, which was unconstrained. Here we present results from new experiments conducted on a late LMO-relevant ferrobasaltic melt. The liquid has an exceptionally low viscosity of 0.22 $+0.11\\atop{-0.19}$to 1.45 $+0.46\\atop{-0.82}$ Pa s at experimental conditions (1,300–1,600°C; 0.1–4.4 GPa) and can be modeled by an Arrhenius relation. Extrapolating to LMO-relevant temperatures, our analysis suggests a low viscosity LMO would form a stratified flotation crust, with the oldest units containing a mafic component and with very pure younger units. Old, impure crust may have been buried by lower crustal diapirs of pure anorthosite in a serial magmatism scenario.

  4. Upper Triassic mafic dykes of Lake Nyos, Cameroon (West Africa) I: K-Ar age evidence within the context of Cameroon Line magmatism, and the tectonic significance

    Science.gov (United States)

    Aka, Festus Tongwa; Hasegawa, Takeshi; Nche, Linus Anye; Asaah, Asobo Nkengmatia Elvis; Mimba, Mumbfu Ernestine; Teitchou, Isidore; Ngwa, Caroline; Miyabuchi, Yasuo; Kobayashi, Tetsuo; Kankeu, Boniface; Yokoyama, Tetsuya; Tanyileke, Gregory; Ohba, Takeshi; Hell, Joseph Victor; Kusakabe, Minoru

    2018-05-01

    The hydrodynamic fragmentation that formed Lake Nyos in northwest Cameroon did not only make it the most unpopular lake in the world from a gas disaster perspective, it also opened a rare and formidable window through which much of the geology of Cameroon can be studied in a single locality. The Cambrian quartz monzonite cliff excavated by the maar-forming explosion and exposed in its northeastern shore is intruded by mafic dykes, two of which we dated. Even though close to one another, the dykes are different in composition. The alkaline dyke yields a slightly older (Carnian) K-Ar fedspar age of 231.1 ± 4.8 Ma, while the sub alkaline dyke yields an age of 224.8 ± 4.7 Ma (Norian). Based on radioisotopic age data available over the last 48 years (347 data) for the Cameroon Line magmatism comprising eruptives and volcano-plutonic complexes, the Nyos dykes are way older than the Cameroon Line, and even pre-date the Lower Cretaceous initiation of west Gondwana fragmentation in Equatorial Atlantic domain. They would therefore not have been directly linked to the formation of the Cameroon Line. Alternatively, they might be associated with the development of intra-continental rift systems in West Central Africa that pre-dated west Gondwana breakup to form the Atlantic Ocean.

  5. U-Pb dating of deformed mafic dyke and host gneiss: implications for understanding reworking processes on the western margin of the Archaean U3o8 Block, NE Sao Francisco Craton, Brazil

    International Nuclear Information System (INIS)

    Oliveira, Elson Paiva

    2000-01-01

    U-Pb ages of deformed mafic dyke and host migmatitic grey gneiss from the transition zone between the Archaen Uaua Block and the Caldeirao Belt are presented. Titanites from the metamorphic dyke's margin and zircons from the gneiss were dated at 2,039 ± 2 Ma and 2,956 ± 39 Ma, respectively. The Sm-Nd data (T DM =2,965 Ma and ε Nd(t) =1.69) on the gneiss, coupled with the U-Pb data on both dyke and gneiss, suggest than an Archaen granodioritic batholith, probably originated at an andean-type continental margin, was intruded by mafic dykes, and subsequently was reworked during the Paleoproterozoic collisional event associated with the development of the Salvador-Curaca Orogen. (author)

  6. A back-arc setting for mafic rocks of the Honeysuckle Beds, southeastern N.S.W.: the use of trace and rare earth element abundances determined by INAA

    Energy Technology Data Exchange (ETDEWEB)

    Dadd, K A [University of Technology, Sydney, NSW (Australia)

    1994-12-31

    Major, trace and rare earth elements abundance in mafic rocks of the Honeysuckle Beds was determined by x-ray fluorescence and neutron activation analysis . A comparison with typical mid-ocean ridge basalt compositions reveals an enrichment in light rare earths elements (Ba, Rb, and Th) and depletion in Nb, Ta and Ti, consistent with modifications of the source by subduction-related fluids. 9 refs., 6 figs.

  7. A back-arc setting for mafic rocks of the Honeysuckle Beds, southeastern N.S.W.: the use of trace and rare earth element abundances determined by INAA

    Energy Technology Data Exchange (ETDEWEB)

    Dadd, K.A. [University of Technology, Sydney, NSW (Australia)

    1993-12-31

    Major, trace and rare earth elements abundance in mafic rocks of the Honeysuckle Beds was determined by x-ray fluorescence and neutron activation analysis . A comparison with typical mid-ocean ridge basalt compositions reveals an enrichment in light rare earths elements (Ba, Rb, and Th) and depletion in Nb, Ta and Ti, consistent with modifications of the source by subduction-related fluids. 9 refs., 6 figs.

  8. UN ENCLAVE DE TURÍSTICO RELIGIOSO

    Directory of Open Access Journals (Sweden)

    Martínez Cárdenas Rogelio

    2011-11-01

    Full Text Available Resumen: La región de los Altos de Jalisco es una zona turística basada en la religiosidad y principalmente en la devoción hacia la Virgen de la Inmaculada Concepción más conocida como “Virgen de San Juan de los Lagos”. Debido a la canonización que hizo el Papa Juan Pablo II de 25 mártires cristeros, han urgido en esta zona, nuevos centros de devoción religiosa. En el caso de Santa Ana de Guadalupe se estima que recibe alrededor de un millón de visitantes anualmente. Es sorprendente el crecimiento logrado por este último santuario. Se ha convertido en un importante centro de turismo religioso; lo asombroso es que está ubicada a 20 kilómetros de San Juan de los Lagos, segundo centro religioso del país, lo que hace aún más interesante la manera en que han podido integrarse estos dos sitios. Palabras clave: Turismo Religioso. Santuario. San Juan de los Lagos, Santo Toribio.

  9. Impact on the deep biosphere of CO2 geological sequestration in (ultra)mafic rocks and retroactive consequences on its fate

    Science.gov (United States)

    Ménez, Bénédicte; Gérard, Emmanuelle; Rommevaux-Jestin, Céline; Dupraz, Sébastien; Guyot, François; Arnar Alfreősson, Helgi; Reynir Gíslason, Sigurőur; Sigurőardóttir, Hólmfríiur

    2010-05-01

    Due to their reactivity and high potential of carbonation, mafic and ultramafic rocks constitute targets of great interest to safely and permanently sequestrate anthropogenic CO2 and thus, limit the potential major environmental consequences of its increasing atmospheric level. In addition, subsurface (ultra)mafic environments are recognized to harbor diverse and active microbial populations that may be stimulated or decimated following CO2 injection (± impurities) and subsequent acidification. However, the nature and amplitude of the involved biogeochemical pathways are still unknown. To avoid unforeseen consequences at all time scales (e.g. reservoir souring and clogging, bioproduction of H2S and CH4), the impact of CO2 injection on deep biota with unknown ecology, and their retroactive effects on the capacity and long-term stability of CO2 storage sites, have to be determined. We present here combined field and experimental investigations focused on the Icelandic pilot site, implemented in the Hengill area (SW Iceland) at the Hellisheidi geothermal power plant (thanks to the CarbFix program, a consortium between the University of Iceland, Reykjavik Energy, the French CNRS of Toulouse and Columbia University in N.Y., U.S.A. and to the companion French ANR-CO2FIX project). This field scale injection of CO2 charged water is here designed to study the feasibility of storing permanently CO2 in basaltic rocks and to optimize industrial methods. Prior to the injection, the microbiological initial state was characterized through regular sampling at various seasons (i.e., October '08, July '09, February '10). DNA was extracted and amplified from the deep and shallow observatory wells, after filtration of 20 to 30 liters of groundwater collected in the depth interval 400-980 m using a specifically developed sampling protocol aiming at reducing contamination risks. An inventory of living indigenous bacteria and archaea was then done using molecular methods based on the

  10. Upper Paleozoic mafic and intermediate volcanic rocks of the Mount Pleasant caldera associated with the Sn-W deposit in southwestern New Brunswick (Canada): Petrogenesis and metallogenic implications

    Science.gov (United States)

    Dostal, Jaroslav; Jutras, Pierre

    2016-10-01

    Upper Paleozoic ( 365 Ma) mafic and intermediate volcanic rocks of the Piskahegan Group constitute a subordinate part of the Mount Pleasant caldera, which is associated with a significant polymetallic deposit (tungsten-molybdenum-bismuth zones 33 Mt ore with 0.21% W, 0.1% Mo and 0.08% Bi and tin-indium zones 4.8 Mt with 0.82% Sn and 129 g/t In) in southwestern New Brunswick (Canada). The epicontinental caldera complex formed during the opening of the late Paleozoic Maritimes Basin in the northern Appalachians. The mafic and intermediate rocks make up two compositionally distinct associations. The first association includes evolved rift-related continental tholeiitic basalts, and the second association comprises calc-alkaline andesites, although both associations were emplaced penecontemporaneously. The basalts have low Mg# 0.34-0.40, smooth chondrite-normalized REE patterns with (La/Yb)n 5-6, primitive mantle-normalized trace element patterns without noticeable negative Nb-Ta anomalies, and their ɛNd(T) ranges from + 2.5 to + 2.2. The basalts were generated by partial melting of a transition zone between spinel and garnet mantle peridotite at a depth of 70-90 km. The calc-alkaline andesites of the second association have chondrite-normalized REE patterns that are more fractionated, with (La/Yb)n 7-8.5, but without significant negative Eu anomalies. Compared to the basaltic rocks, they have lower ɛNd(T) values, ranging from + 0.5 to + 1.9, and their mantle-normalized trace element plots show negative Nb-Ta anomalies. The ɛNd(T) values display negative correlations with indicators of crustal contamination, such as Th/La, Th/Nb and SiO2. The andesitic rocks are interpreted to have formed by assimilation-fractional crystallization processes, which resulted in the contamination of a precursor basaltic magma with crustal material. The parent basaltic magma for both suites underwent a different evolution. The tholeiitic basalts experienced shallow-seated fractional

  11. Zircon and baddeleyite from the economic ultramafic-mafic Noril'sk-1 intrusion (Russia): Hf-isotope constraints on source composition

    Science.gov (United States)

    Malitch, K. N.; Belousova, E. A.; Badanina, I. Yu.; Griffin, W. L.

    2012-04-01

    The ultramafic-mafic Noril'sk-1 intrusion in the northwestern part of the Siberian Craton (Russia) represents one of three known Noril'sk-type, ore-bearing intrusions, which host one of the world's major economic sulphide platinum-group-element (PGE)-Cu-Ni deposits. Zircon and baddeleyite dated previously both by SHRIMP (i.e. 248.0 ± 3.7 Ma, Campbell et al. 1992) and ID-TIMS (251.1 ± 3.6 Ma, Kamo et al. 1996) have been restricted to one lithology (e.g. leucogabbro) of the Noril'sk-1 intrusion. To better constrain the age of igneous event and sources involved in its generation our multi-technique study utilized ten rock samples characteristic of unmineralized and mineralized lithologies. The rocks investigated comprise (from top to bottom) gabbro-diorite (sample N1-1), leucogabbro (N1-3), olivine-free gabbro (N1-2 and N1-4), olivine-bearing gabbro (N1-5), olivine gabbro (N1-6), plagiowehrlite and plagiodunite (N1-7), taxitic-textured rocks comprising melanotroctolite, olivine gabbro with relics of ultramafic rocks (N1-8, N1-9) and contact fine-grained gabbro (N1-10). Sulphide PGE-Cu-Ni ores occur in ultramafic (N1-7) and taxitic-textured rocks (N1-8 and N1-9), which have thickness of about 17 m, whereas the low-sulphide horizon of about 1 m thick occurs in the upper part of intrusion (N1-3). In situ U-Pb analyses of zircon from these rocks, combined with detailed study of crystal morphology and internal structure, identify four zircon populations (Malitch et al. 2012). The U-Pb ages of baddeleyite and the defined zircon populations cover a significant time span, from Late Paleozoic to Early Mesozoic (e.g., 290 ± 2.8; 261.3 ± 1.6; 245.7 ± 1.1; 236.5 ± 1.8 and 226.7 ± 0.9 Ma). The established distribution of U-Pb ages implies that crystallization of baddeleyite and zircon corresponds to several stages of protracted evolution of ultramafic-mafic magmas at deep-seated staging chambers and/or probably characterizes interaction of distinct magmas during formation

  12. Trace element partitioning in rock forming minerals of co-genetic, subduction-related alkaline and tholeiitic mafic rocks in the Ural Mountains, Russia

    Science.gov (United States)

    Krause, J.; Brügmann, G. E.; Pushkarev, E. V.

    2009-04-01

    The partitioning of trace elements between rock forming minerals in igneous rocks is largely controlled by physical and chemical parameters e.g. temperature, pressure and chemical composition of the minerals and the coexisting melt. In the present study partition coefficients for REE between hornblende, orthopyroxene, feldspars, apatite and clinopyroxene in a suite of co-genetic alkaline and tholeiitic mafic rocks from the Ural Mountains (Russia) were calculated. The results give insights to the influence of the chemical composition of the parental melt on the partitioning behaviour of the REE. Nepheline-bearing, alkaline melanogabbros (tilaites) are assumed to represent the most fractionated products of the melt that formed the ultramafic cumulates in zoned mafic-ultramafic complexes in the Ural Mountains. Co-genetic with the latter is a suite of olivine gabbros, gabbronorites and hornblende gabbros formed from a tholeiitic parental melt. Negative anomalies for the HFSE along with low Nb and Ta contents and a positive Sr anomaly indicate a subduction related origin of all parental melts. The nepheline gabbros consist predominantly of coarse-grained clinopyroxene phenocrysts in a matrix of fine grained clinopyroxene, olivine, plagioclase, K-feldspar and nepheline with accessory apatite. The tholeiitic gabbros have equigranular to porphyric textures with phenocrysts of olivine, pyroxene and hornblende in a plagioclase rich matrix with olivine hornblende, pyroxene and accessory apatite. Element concentrations of adjacent matrix grains and rims of phenochrysts were measured with LA-ICPMS. The distribution of REE between hornblende and clinopyroxene in the tholeiitic rocks is similar for most of the elements (DHbl•Cpx(La-Tm) = 2.7-2.8, decreasing to 2.6 and 2.4 for Yb and Lu, respectively). These values are about two times higher than published data (e.g. Ionov et al. 1997). Partition coefficients for orthopyroxene/clinopyroxene systematically decrease from the HREE

  13. Field, geochemistry and Sr-Nd isotopes of the Pan-African granitoids from the Tifnoute Valley (Sirwa, Anti-Atlas, Morocco): a post-collisional event in a metacratonic setting

    Science.gov (United States)

    Toummite, A.; Liegeois, J. P.; Gasquet, D.; Bruguier, O.; Beraaouz, E. H.; Ikenne, M.

    2013-10-01

    In the Tifnoute Valley, three plutonic units have been defined: the Askaoun intrusion, the Imourkhssen intrusion and the Ougougane group of small intrusions. They are made of quartz diorite, granodiorite and granite and all contain abundant mafic microgranular enclaves (MME). The Askaoun granodiorite and the Imourkhssen granite have been dated by LA-ICP-MS on zircon at 558 ± 2 Ma and 561 ± 3 Ma, respectively. These granitic intrusions are subcontemporaneous to the widespread volcanic and volcano-detrital rocks from the Ouarzazate Group (580-545 Ma), marking the post-collisional transtensional period in the Anti-Atlas and which evolved towards alkaline and tholeiitic lavas in minor volume at the beginning of the Cambrian anorogenic intraplate extensional period. Geochemically, the Tifnoute Valley granitoids belong to an alkali-calcic series (high-K calc-alkaline) with typical Nb-Ta negative anomalies and no alkaline affinities. Granitoids and enclaves display positive ɛNd-560Ma (+0.8 to +3.5) with young Nd-TDM between 800 and 1200 Ma and relatively low 87Sr/86Sr initial ratios (Sri: 0.7034 and 0.7065). These values indicate a mainly juvenile source corresponding to a Pan-African metasomatized lithospheric mantle partly mixed with an old crustal component from the underlying West African Craton (WAC). Preservation in the Anti-Atlas of pre-Pan-African lithologies (c. 2.03 Ga basement, c. 800 Ma passive margin greenschist-facies sediments, allochthonous 750-700 Ma ophiolitic sequences) indicates that the Anti-Atlas lithosphere has not been thickened and was never an active margin during the Neoproterozoic. After a transpressive period, the late Ediacaran period (580-545 Ma) is marked by movement on near vertical transtensional faults, synchronous with the emplacement of the huge Ouarzazate Group and the Tifnoute Valley granitoids. We propose here a geodynamical model where the Tifnoute Valley granitoids as well as the Ouarzazate Group were generated during the post

  14. The Ilha Anchieta Quartz Monzonite: the southernmost expression of ca. 500 Ma post-collisional magmatism in the Ribeira Belt

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    José M. Azevedo Sobrinho

    2011-09-01

    Full Text Available The Ilha Anchieta Quartz Monzonite (IAQM occupies most of the homonymous island in the coast of the state of São Paulo, and is intrusive into foliated rocks of the ~565 Ma Ubatuba Charnockite. The main petrographic variety is a porphyritic biotite-hornblende quartz monzonite with 2-4 cm tabular microcline megacrysts set in a medium-grained groundmass and magmatic foliation. Outcrop-scale structures indicate cumulative processes (modal and grain-size magmatic banding and interaction with basic magmas (mafic microgranular enclaves. Lithogeochemical data indicates that the main variety is intermediate to acid (S1O2 = 63-67%, alkali-calcic, metaluminous and magnesian (mg# ~30, showing moderate Sr (300-400 ppm and Ba (~1500 ppm contents and relatively high HFSE (Nb = 40 ppm; Zr = 550-700 ppm. The older charnockites are more silicic (S1O2 = 71-78%, ferroan(mg# = 12-16, and have very low Sr (13-80 ppm contents, resulting in Ba/Sr ratios remarkably higher than the IAQM (10 versus 4. LA-MC-ICPMS U-Pb zircon dating of the IAQM yielded 499.7 ± 5.9 Ma. This is the youngest magmatic age identified so far in the crystalline basement of the state of São Paulo, and indicates that the pluton is the southernmost expression of the post-collisional "G5" magmatism in the Ribeira Belt.O Quartzo Monzonito Ilha Anchieta (QMIA ocupa a maior parte da ilha homônima na região costeira do Estado de São Paulo, e é intrusivo em rochas foliadas do Charnockito Ubatuba (~565 Ma. A principal variedade petrográfica é um biotitahornblenda quartzo monzonito porfirítico com foliação magmática e megacristais tabulares de microclínio com 2-4 cm em matriz de granulação média. Estruturas em afloramento indicam processos cumuláticos (bandamento modal e granulométrico e interação com magmas básicos (enclaves microgranulares máficos. Dados geoquímicos indicam que a variedade principal é intermediária a ácida (SiO2 = 63-67%, tem caráter

  15. Brittle-ductile deformation effects on zircon crystal-chemistry and U-Pb ages: an example from the Finero Mafic Complex (Ivrea-Verbano Zone, western Alps)

    Science.gov (United States)

    Langone, Antonio; José Alberto, Padrón-Navarta; Zanetti, Alberto; Mazzucchelli, Maurizio; Tiepolo, Massimo; Giovanardi, Tommaso; Bonazzi, Mattia

    2016-04-01

    A detailed structural, geochemical and geochronological survey was performed on zircon grains from a leucocratic dioritic dyke discordantly intruded within meta-diorites/gabbros forming the External Gabbro unit of the Finero Mafic Complex. This latter is nowadays exposed as part of a near complete crustal section spanning from mantle rocks to upper crustal metasediments (Val Cannobina, Ivrea-Verbano Zone, Italy). The leucocratic dyke consists mainly of plagioclase (An18-24Ab79-82Or0.3-0.7) with subordinate amounts of biotite, spinel, zircon and corundum. Both the leucocratic dyke and the surrounding meta-diorites show evidence of ductile deformation occurred under amphibolite-facies conditions. Zircon grains (up to 2 mm in length) occur mainly as euhedral grains surrounded by fine grained plagioclase-dominated matrix and pressure shadows, typically filled by oxides. Fractures and cracks within zircon are common and can be associated with grain displacement or they can be filled by secondary minerals (oxides and chlorite). Cathodoluminescence (CL) images show that zircon grains have internal features typical of magmatic growth, but with local disturbances. However EBSD maps on two selected zircon grains revealed a profuse mosaic texture resulting in an internal misorientation of ca. 10o. The majority of the domains of the mosaic texture are related to parting and fractures, but some domains show no clear relation with brittle features. Rotation angles related to the mosaic texture are not crystallographically controlled. In addition, one of the analysed zircons shows clear evidence of plastic deformation at one of its corners due to indentation. Plastic deformation results in gradual misorientations of up to 12o, which are crystallographically controlled. Trace elements and U-Pb analyses were carried out by LA-ICP-MS directly on petrographic thin sections and designed to cover the entire exposed surface of selected grains. Such investigations revealed a strong

  16. An example of post-collisional mafic magmatism: the gabbro-anorthosite layered complex from the Tin Zebane area (western Hoggar, Algeria)

    Science.gov (United States)

    Aı̈t-Djafer, Saı̈da; Ouzegane, Khadidja; Paul-Liégeois, Jean; Kienast, Jean Robert

    2003-10-01

    The Tin Zebane gabbro-anorthosite layered mafic intrusion represented by plagioclase-rich cumulates forms a set of small lenticular to round-shaped mainly undeformed bodies intruding the Pan-African high-pressure metamorphic rocks from western Hoggar (Tuareg shield, southwest Algeria). The coarse-grained anorthosites are mainly made of slightly zoned bytownite (An 86-74) with the higher anorthite content at the cores. Anorthosites are interlayered with leucogabbros and gabbros that show preserved magmatic structures and with olivine gabbros characterised by coronitic textures. The primary assemblage in gabbros includes plagioclase (An 93-70), olivine (Fo 77-70), zoned clinopyroxene (En 43-48Fs 05-13Wo 41-49 with Al 2O 3 up to 4.3 wt.%) and rare orthopyroxene (En 73-78). Pyroxenes and olivine are commonly surrounded by Ca-amphibole. The olivine-plagioclase contact is usually marked by a fine orthopyroxene-Cr-spinel-amphibole symplectite. A magnesian pigeonite (En 70-75Fs 19-20Wo 6-10) is also involved in corona. The coronitic minerals have equilibrated with the primary mineral rims at P- T- aH2O conditions of 797 ± 42 °C for aH2O=0.5 and 808 ± 44 °C for aH2O=0.6 at 6.2 ± 1.4 kbar. The Tin Zebane gabbroic rocks are depleted in REE with a positive Eu anomaly, high Sr (>10 ∗ chondrite) and Al 2O 3 concentrations (17-33%) that support plagioclase accumulation with the extreme case represented by the anorthosites. The REE patterns can be modelised using plagioclase, clinopyroxene and orthopyroxene REE signature, without any role played by accessory minerals. High MgO content points to olivine as a major cumulate phase. Anorthositic gabbros Sr and Nd isotopic initial ratios are typical of a depleted mantle source (Sr i=0.70257-0.70278; ɛNd=+5.9 to +7.8). This isotopic signature is identical to that of the 10-km wide 592 Ma old dyke complex composed of alkaline to peralkaline granites and tholeiitic gabbros and one single bimodal complex can be inferred. The source

  17. Petrology, geochemistry and tectonic setting of alkaline mafic rocks in the Jalal Abad area in the NW of Zarand (Kerman Province: Evidence for Paleo-Tethys rifting in the Central Iran

    Directory of Open Access Journals (Sweden)

    Yusef Vesali

    2018-03-01

    Full Text Available The Jalal Abad region lies within the southern sector of Posht Badam block near to Jalal Abad, Najaf Abad iron deposits. In this region, several mafic intrusions and associated dyke and sills were intruded within the volcano-sedimentary unit of Rizu series and magnetite veins producing a narrow contact metamorphic aureole and overlain by Desu Series dolomites. These intrusion massives include irregular coarse- grained gabbro- diorites stocks and several NW-SE-trending basaltic dykes and sills. Petrographical and geochemical studies on the Jalal Abad mafic units reveal that they are alkaline in nature and based on the tectonic discrimination diagrams are grouped in alkaline basalts field of the intra-continental rift setting. They display LREE enrichment and HREE depletion, and significant enrichment in LILE in comparison to HFSE and HREE. Compositionally, they resemble modern OIB and the Hawaiian alkaline basalts. Magmas of these OIB-type and alkaline rock associations formed from partial melting of garnet- lherzolite facieses in the plume source, during the rift-drift and seafloor spreading evolution of the Proto-Tethys oceanic lithosphere during the Ordovician through Silurian periods.

  18. Geochronology and geochemistry of the Borohoro pluton in the northern Yili Block, NW China: Implication for the tectonic evolution of the northern West Tianshan orogen

    Science.gov (United States)

    Wang, Meng; Zhang, Jinjiang; Zhang, Bo; Liu, Kai; Chen, Youxin; Zheng, Yanrong

    2018-03-01

    The closure of the North Tianshan Ocean between the Junggar Terrane and the Yili Block is a longtime debated issue in literature, because of the different understanding of the Carboniferous volcanic rocks in the northern margin of the Yili Block. This study presents new geochronological and whole-rock geochemical data for the granitic rocks from the Borohoro pluton to provide constraints on the tectonic regime for the northern West Tianshan during the Carboniferous. LA-ICP-MS U-Pb dating results reveal two magmatic phases for the Borohoro pluton. The former magmatic activity in the Early Carboniferous formed the fine-grained granodiorite (332 Ma). The later magmatic activity occurred during the Late Carboniferous (305-300 Ma), forming a diversity of granitic rocks, involving quartz diorite, granodiorite and granite. Geochemical and mineralogical studies reveal that the studied granitic rocks from the Borohoro pluton all belong to metaluminous to weakly peraluminous, calc-alkaline I-type granites. They are characterized by enrichment in LILEs relative to HFSEs, and depletion of Nb, Ti and P, typical of continental arc-type granites. The intermediate SiO2, high Al2O3, and relatively low Fe2O3T, MgO and TiO2 contents reflect that these granitic rocks are mainly crust-derived. But the high Mg# values for most samples and the occurrence of microgranular mafic enclaves indicate that their magma sources were mixed by mantle-derived components. Especially, the Late Carboniferous rocks define an elegant mixing trend in both the Rb-Rb/V and the 1/V-Rb/V diagrams, consistent with mixing between magmas from subcontinental lithospheric mantle and mafic lower crust. Taking into consideration of the facts that all the Devonian to Carboniferous granitoids belong to calc-alkaline I-type granites, and granitoids of A-type didn't appear until the Early Permian, we suggest that the subduction of the North Tianshan Ocean continued to the Late Carboniferous, generating the granitic

  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. Formación de megacristales de feldespato potásico en el sector sur del batolito Cerro Aspero-Alpa Corral (32°40'S y 64°50'W, Sierras Pampeanas, Córdoba, Argentina

    Directory of Open Access Journals (Sweden)

    Pinotti, L. P.

    1992-12-01

    Full Text Available The surrounding rocks of studied area are composed by a metamorphic sequence which includes gneisses, schists, amphibolites, marbles and heterogeneous migmatites in non-conformity intruded by a granitic pluton. All this sequence is dated as having late-Precambric to mid-Paleozoic age.Three facies, mostly of monzogranitic composition, were identified. This study focuses on the porphiric facies; detailed petroestructural studies being performed, the orientation of large microcline crystal and associated microgranular enclaves being measured.Different primary flow directions were determined with track variation of microcline megacrystal and enclaves from subvertical to nearly horizontal positions.These changes have been interpreted as a convective system within the pluton.The presence of a marked planar fabric in microcline megacrystals along with phenomena such a size-variation of crystal, synneusis, crystal trending at the enclave's border and crystal accumulation, proves their early magmatic origin. The enclaves show a cinematic of deformation produced by simple shear.El entorno encajante de la zona estudiada está integrado por una secuencia metamórfica que incluye gneises, esquistos, anfibolitas, calizas cristalinas y migmatitas heterogéneas, intruidas discordantemente por el plutón granítico. A este conjunto puede asignársele una edad precámbrica superior-paleozoica media.Se identificaron tres facies, en su mayoría de composición monzogranítica, diques micrograníticos a aplíticos y enclaves. En este trabajo se pone énfasis en la facies porfiroide efectuándose estudios petroestructurales de detalle, tomando como indicadores la orientación de los grandes cristales de microclina y enclaves microgranulares asociados.Se determinaron distintas direcciones de flujo primario con variaciones en la trayectoria de los megacristales de microclina y enclaves desde posiciones subverticales hasta aproximadamente horizontales. Estos cambios han

  1. Geochronological, geochemical, and Sr-Nd-Hf isotopic characteristics of Cretaceous monzonitic plutons in western Zhejiang Province, Southeast China: New insights into the petrogenesis of intermediate rocks

    Science.gov (United States)

    Liu, Liang; Qiu, Jian-Sheng; Zhao, Jiao-Long; Yang, Ze-Li

    2014-05-01

    We present comprehensive petrological, geochemical, and Sr-Nd-Hf isotopic data for the Matou and Dalai plutons in western Zhejiang Province, Southeast China, with the aim of constraining the petrogenesis of monzonites and to offer new insights into the deep processes of interaction between crustal- and mantle-derived magmas beneath SE China. The Matou pluton comprises quartz monzonite, whereas the Dalai pluton consists of quartz monzodiorite. Zircon U-Pb ages obtained by laser ablation-inductively coupled plasma-mass spectrometry show that both plutons were emplaced at 99-101 Ma. Rocks of both plutons are intermediate to silicic, metaluminous to weakly peraluminous, subalkaline, and K-rich in composition. Samples of the plutons are enriched in large ion lithophile (e.g., Rb, K, and Pb) and light rare earth elements, depleted in high-field strength elements (e.g., Nb, Ta, and Ti), and have small negative or no Eu anomalies. In addition, the rocks have high Mg# values (up to 53.9), high zircon ɛHf(t) values (up to - 1.4), and low Nb/U and Ta/U ratios. Geochemical evidence suggests that both depleted asthenospheric and metasomatically enriched mantle components were involved in the formation of these monzonitic rocks. The presence of inherited zircons with Palaeoproterozoic ages and zircons with unusually low ɛHf(t) values (- 12.9) in the Matou quartz monzonites indicates that ancient crustal materials were also involved in their petrogenesis. In combination with the presence of abundant mafic microgranular enclaves (MMEs) with spheroidal to ellipsoidal-ovoidal shapes and xenocrysts within the more diffused enclaves, and the results of trace element modelling, we suggest that the Matou quartz monzonites were generated by mixing between mantle-derived mafic magmas and crustally derived silicic magmas. The Dalai pluton is relatively homogeneous and contains fewer MMEs than the Matou pluton. Zircons from the Dalai pluton show no inherited components, indicating that

  2. MetaRep, an extended CMAS 3D program to visualize mafic (CMAS, ACF-S, ACF-N) and pelitic (AFM-K, AFM-S, AKF-S) projections

    Science.gov (United States)

    France, Lydéric; Nicollet, Christian

    2010-06-01

    MetaRep is a program based on our earlier program CMAS 3D. It is developed in MATLAB ® script. MetaRep objectives are to visualize and project major element compositions of mafic and pelitic rocks and their minerals in the pseudo-quaternary projections of the ACF-S, ACF-N, CMAS, AFM-K, AFM-S and AKF-S systems. These six systems are commonly used to describe metamorphic mineral assemblages and magmatic evolutions. Each system, made of four apices, can be represented in a tetrahedron that can be visualized in three dimensions with MetaRep; the four tetrahedron apices represent oxides or combination of oxides that define the composition of the projected rock or mineral. The three-dimensional representation allows one to obtain a better understanding of the topology of the relationships between the rocks and minerals and relations. From these systems, MetaRep can also project data in ternary plots (for example, the ACF, AFM and AKF ternary projections can be generated). A functional interface makes it easy to use and does not require any knowledge of MATLAB ® programming. To facilitate the use, MetaRep loads, from the main interface, data compiled in a Microsoft Excel ™ spreadsheet. Although useful for scientific research, the program is also a powerful tool for teaching. We propose an application example that, by using two combined systems (ACF-S and ACF-N), provides strong confirmation in the petrological interpretation.

  3. 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)

  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. Interaction of the lithospheric mantle and crustal melts for the generation of the Horoz pluton (Niğde, Turkey: whole-rock geochemical and Sr–Nd–Pb isotopic evidence

    Directory of Open Access Journals (Sweden)

    Kerim Kocak

    2016-08-01

    Full Text Available The Horoz pluton includes granitic and granodioritic rocks, with widespread mafic microgranular enclaves (MMEs. Petrochemically, the rocks of the pluton show calc-alkaline to shoshonitic and metaluminous to slightly peraluminous composition. The rocks also exhibit an enrichment in large ion lithophile elements, e.g. Rb, K, and depletions of high field strength elements such as Y, Lu, and Mg#, Ni, with a slightly concave-upward rare earth element pattern. Both granitic and granodioritic rocks exhibit geochemical characteristics of tonalite, trondhjemite and granodiorite assemblages, possibly developed by the partial melting of a thickened lower crust. The granitoids have high concentrations of Na2O (2.6–4.5 wt%, Sr (347–599 ppm, intermediate-high (La/YbN (8.2–18.1, mostly >11 , Al2O3 (13.2–16.9 wt%, average 15.3 wt%, low MgO (0.2–1.4 wt%, average 0.84 wt% and Co (0.7–10.3 ppm. The MMEs include higher Na2O (4.5–5.5 wt%, Sr (389–1149 ppm, Al2O3 (16.9–19.2 wt%, average 17.8 wt%, MgO (1.4–4.4 wt%, average 2.75 wt% and Co (6.2–18.7 ppm contents in comparison with that of their hosts. There is a lack of negative Eu anomalies, except a few samples. Both host rocks and MMEs have a low initial 87Sr/86Sr ratio (respectively 0.7046–0.7051 and 0.7047–0.7058, low eNd value (–1.8 to –0.2 and –0.6 to 0.7 at 50 Ma and highly radiogenic 208Pb/204Pb ratios (39.43–39.47 and 39.39–39.54. Whole-rock chemistry and isotopic data suggest that parent magmas of both MMEs and their hosts have derived from melts of the mixing between the lithospheric mantle and crustal end members, than fractional crystallization processes in crustal levels.

  6. Natural factors and mining activity bearings on the water quality of the Choapa basin, North Central Chile: insights on the role of mafic volcanic rocks in the buffering of the acid drainage process.

    Science.gov (United States)

    Parra, Amparo; Oyarzún, Jorge; Maturana, Hugo; Kretschmer, Nicole; Meza, Francisco; Oyarzún, Ricardo

    2011-10-01

    This contribution analyzes water chemical data for the Choapa basin, North Central Chile, for the period 1980-2004. The parameters considered are As, Cu Fe, pH, EC, SO₄⁻², Cl⁻¹, and HCO[Formula: see text], from samples taken in nine monitoring stations throughout the basin. Results show rather moderate contents of As, Cu, and Fe, with the exception of the Cuncumén River and the Aucó creek, explained by the influence of the huge porphyry copper deposit of Los Pelambres and by the presence of mining operations, respectively. When compared against results obtained in previous researches at the neighboring Elqui river basin, which host the El Indio Au-Cu-As district, a much reduced grade of pollution is recognized for the Choapa basin. Considering the effect of acid rock drainage (ARD)-related Cu contents on the fine fraction of the sediments of both river basins, the differences recorded are even more striking. Although the Los Pelambres porphyry copper deposit, on the headwaters of the Choapa river basin, is between one and two orders of magnitude bigger than El Indio, stream water and sediments of the former exhibit significantly lower copper contents than those of the latter. A main factor which may explain these results is the smaller degree of H( + )-metasomatism on the host rocks of the Los Pelambres deposit, where mafic andesitic volcanic rocks presenting propylitic hydrothermal alteration are dominant. This fact contrast with the highly altered host rocks of El Indio district, where most of them have lost their potential to neutralize ARD.

  7. Petrography, geochemistry and geochronology of the host porphyries and associated alteration at the Tuwu Cu deposit, NW China: a case for increased depositional efficiency by reaction with mafic hostrock?

    Science.gov (United States)

    Shen, Ping; Pan, Hongdi; Zhou, Taofa; Wang, Jingbin

    2014-08-01

    Tuwu is the largest porphyry copper deposit discovered in the Eastern Tianshan Mountains, Xinjiang, China. A newly recognized volcanic complex in the Early Carboniferous Qi'eshan Group at Tuwu consists of basalt, andesite, and diorite porphyry. The plagiogranite porphyry was emplaced into this complex at 332.8±2.5 Ma (U-Pb zircon SIMS determination). Whole-rock element geochemistry shows that the volcanic complex and plagiogranite porphyry formed in the same island arc, although the complex was derived by partial melting of the mantle wedge and the plagiogranite porphyry by partial melting of a subducting slab. The diorite and the plagiogranite porphyries have both been subjected to intense hydrothermal alteration and associated mineralization, but the productive porphyry is the plagiogranite porphyry. Three alteration and mineralization stages, including pre-, syn- and post-ore stages, have been recognized. The pre-ore stage formed a barren propylitic alteration which is widespread in the volcanic complex. The syn-ore stage is divided into three sub-stages: Stage 1 is characterized by potassic alteration with chalcopyrite + bornite + chalcocite; Stage 2 is marked by chlorite-sericite-albite alteration with chalcopyrite ± pyrite ± bornite; Stage 3 is represented by phyllic alteration with chalcopyrite + pyrite ± molybdenite. The post-ore stage produced a barren argillic alteration limited to the diorite porphyry. A specific feature of the Tuwu deposit is that the productive porphyry was emplaced into a very mafic package, and reaction of the resulting fluids with the ferrous iron-rich hostrocks was a likely reason that Tuwu is the largest porphyry in the district.

  8. Comment on ;Evolution of high-pressure mafic granulites and pelitic gneisses from NE Madagascar: Tectonic implications;. Tectonophysics, 662, 219-242 (2015) by Ishwar-Kumar et al.

    Science.gov (United States)

    Goncalves, Philippe; Brandt, Sönke; Nicollet, Christian; Tucker, Robert

    2017-05-01

    Determining the possible tectonic regimes active during the Neoproterozoic is crucial for the knowledge of the evolution of the super-continent Gondwana. In Madagascar, that occupies a key position in Gondwana, there is an on-going debate regarding the location of possible suture zones and the implications in terms of paleo-geography. Recognizing high-pressure to ultra-high pressure conditions in mafic rocks is commonly viewed as a strong argument for paleo-subduction zones. Ishwar-Kumar et al. (2015) report unusual high pressure conditions (24 kbar) in Neoproterozoic to Cambrian rocks from North-Central Madagascar (Andriamena Complex). They propose a geodynamic model in which exhumation of the high pressure terranes from up to 80 km to 40 km occurred via vertical extrusion during the collision of various crustal blocks after subduction and closure of an oceanic domain during the formation of Gondwana in the late Neoproterozoic to Cambrian. We question this model and in particular the (ultra-)high pressure conditions reported, because their estimation is based on a misinterpretation of the petrography and inaccurate thermodynamic modeling for the crucial metabasite sample. The authors suggest that garnet-quartz coronas around orthopyroxene and ilmenite coexist with clinopyroxene. The postulated garnet-clinopyroxene-quartz assemblage is interpreted to document an eclogite facies overprint. However, the presence of abundant plagioclase in the sample and the lack of high jadeite content in clinopyroxene clearly refute the postulated eclogite facies conditions. According to the presented photographs clinopyroxene is part of the rock matrix. We therefore suggest that the sample represents a common two-pyroxene granulite, formed at mid- to low-pressure granulite facies conditions of > 700 °C and Madagascar, this interpretation is not justified by the data presented by Ishwar-Kumar et al. (2015).

  9. The Ediacaran volcanic rocks and associated mafic dykes of the Ouarzazate Group (Anti-Atlas, Morocco): Clinopyroxene composition, whole-rock geochemistry and Sr-Nd isotopes constraints from the Ouzellarh-Siroua salient (Tifnoute valley)

    Science.gov (United States)

    Belkacim, Said; Gasquet, Dominique; Liégeois, Jean-Paul; Arai, Shoji; Gahlan, Hisham A.; Ahmed, Hassan; Ishida, Yoshito; Ikenne, Moha

    2017-03-01

    Belonging to the huge Ouarzazate volcanic Group that covered the whole Anti-Atlas during the late Ediacaran (580-545 Ma), the Tifnoute valley volcanic formations are mainly pyroclastic and show a large composition, from trachybasalt to rhyolite and are crosscut by dolerite dykes. The Tifnoute valley volcanic rocks are located within a rigid salient of the Anti-Atlas that gives them special extreme characteristics. Due to the heavy greenschist alteration that affects this volcanic group, we focused the more immobile elements, but as REE can also be affected, we used the composition of unaltered clinopyroxene crystals to determine the nature of these volcanic rocks. The clinopyroxene is an augite diopside in the basalt, an augite in the andesite and an augite-salite in the dolerite. Petrography of the Tifnoute mafic volcanic rocks and clinopyroxene compositions indicate the presence of two magmatic series: (i) older high-K calc-alkaline (alkali-calcic) andesite and basalt characterized by the early crystallization of Fe-Ti oxides and of the late fractionation of plagioclase, the modal proportion of the latter increasing from the basalt to the andesite and (ii) younger alkalic dolerite dykes. With clinopyroxene trace element compositions obtained using laser ablation ICP-MS, we calculated the composition of the melts in equilibrium with the pyroxenes. The volcanic rocks of the Tifnoute Valley have positive εNd570 (+1.7 to +5.0), low Sri (volcanic rocks emplaced in a Pan-African transtensive post-collisional environment that evolved towards the major rifting event that will give rise to the Rheic ocean, in a similar way to what occurred just after the Variscan orogeny during the Triassic period that evolved to the Tethys ocean opening.

  10. Magnetic properties of electroplated nano/microgranular NiFe thin films for rf application

    NARCIS (Netherlands)

    Zhuang, Y.; Vroubel, M.; Rejaei, B.; Burghartz, J.N.; Attenborough, K.

    2005-01-01

    A granular NiFe thin film with large in-plane magnetic anisotropy and high ferromagnetic-resonance frequency developed for radio-frequency integrated circuit (IC) applications is presented. During the deposition, three-dimensional (3D) growth occurs, yielding NiFe grains (? ? 1.0??m). Nanonuclei (?

  11. Mafic magmatism in the Bakhuis Granulite Belt

    NARCIS (Netherlands)

    Klaver, M.; de Roever, E.W.F.; Thijssen, A.C.D.; Bleeker, W.; Söderlund, U.; Chamberlain, K.; Ernst, R.; Berndt, J.; Zeh, A.

    2015-01-01

    The Bakhuis Granulite Belt (BGB) is a metamorphic terrain within the Guiana Shield that experienced ultrahigh-temperature (UHT) metamorphism at 2.07–2.05Ga. In the southwest of the BGB, the Kabalebo charnockites were emplaced at ca. 1.99Ga and thus postdate UHT metamorphism by at least 60Myr. Two

  12. Timescale of Petrogenetic Processes Recorded in the Mount Perkins Magma System, Northern Colorado River Extension Corridor, Arizona

    Science.gov (United States)

    Danielson, Lisa R.; Metcalf, Rodney V.; Miller, Calvin F.; Rhodes Gregory T.; Wooden, J. L.

    2013-01-01

    The Miocene Mt. Perkins Pluton is a small composite intrusive body emplaced in the shallow crust as four separate phases during the earliest stages of crustal extension. Phase 1 (oldest) consists of isotropic hornblende gabbro and a layered cumulate sequence. Phase 2 consists of quartz monzonite to quartz monzodiorite hosting mafic microgranitoid enclaves. Phase 3 is composed of quartz monzonite and is subdivided into mafic enclave-rich zones and enclave-free zones. Phase 4 consists of aphanitic dikes of mafic, intermediate and felsic compositions hosting mafic enclaves. Phases 2-4 enclaves record significant isotopic disequilibrium with surrounding granitoid host rocks, but collectively enclaves and host rocks form a cogenetic suite exhibiting systematic variations in Nd-Sr-Pb isotopes that correlate with major and trace elements. Phases 2-4 record multiple episodes of magma mingling among cogenetic hybrid magmas that formed via magma mixing and fractional crystallization at a deeper crustal. The mafic end-member was alkali basalt similar to nearby 6-4 Ma basalt with enriched OIB-like trace elements and Nd-Sr-Pb isotopes. The felsic end-member was a subalkaline crustal-derived magma. Phase 1 isotropic gabbro exhibits elemental and isotopic compositional variations at relatively constant SiO2, suggesting generation of isotropic gabbro by an open-system process involving two mafic end-members. One end-member is similar in composition to the OIB-like mafic end-member for phases 2-4; the second is similar to nearby 11-8 Ma tholeiite basalt exhibiting low epsilon (sub Nd), and depleted incompatible trace elements. Phase 1 cumulates record in situ fractional crystallization of an OIB-like mafic magma with isotopic evidence of crustal contamination by partial melts generated in adjacent Proterozoic gneiss. The Mt Perkins pluton records a complex history in a lithospheric scale magma system involving two distinct mantle-derived mafic magmas and felsic magma sourced in the

  13. Enclaves of genetic diversity resisted Inca impacts on population history.

    Science.gov (United States)

    Barbieri, Chiara; Sandoval, José R; Valqui, Jairo; Shimelman, Aviva; Ziemendorff, Stefan; Schröder, Roland; Geppert, Maria; Roewer, Lutz; Gray, Russell; Stoneking, Mark; Fujita, Ricardo; Heggarty, Paul

    2017-12-12

    The Inca Empire is claimed to have driven massive population movements in western South America, and to have spread Quechua, the most widely-spoken language family of the indigenous Americas. A test-case is the Chachapoyas region of northern Peru, reported as a focal point of Inca population displacements. Chachapoyas also spans the environmental, cultural and demographic divides between Amazonia and the Andes, and stands along the lowest-altitude corridor from the rainforest to the Pacific coast. Following a sampling strategy informed by linguistic data, we collected 119 samples, analysed for full mtDNA genomes and Y-chromosome STRs. We report a high indigenous component, which stands apart from the network of intense genetic exchange in the core central zone of Andean civilization, and is also distinct from neighbouring populations. This unique genetic profile challenges the routine assumption of large-scale population relocations by the Incas. Furthermore, speakers of Chachapoyas Quechua are found to share no particular genetic similarity or gene-flow with Quechua speakers elsewhere, suggesting that here the language spread primarily by cultural diffusion, not migration. Our results demonstrate how population genetics, when fully guided by the archaeological, historical and linguistic records, can inform multiple disciplines within anthropology.

  14. Punjabi Orchard Farmers: An Immigrant Enclave in Rural California.

    Science.gov (United States)

    Gibson, Margaret A.

    1988-01-01

    Examines the adaptation patterns of Punjabi Sikh orchard farmers in rural California. Discusses the role of the following: (1) the historical context of immigration; (2) the immigrants' perceptions of their particular situation; (3) the group's cultural traditions; and (4) 1965 Immigration Act. (FMW)

  15. Trace element characteristics of mafic and ultramafic meta-igneous rocks from the 3.5 Ga. Warrawoona group: evidence for plume-lithosphere interaction beneath Archaean continental crust

    International Nuclear Information System (INIS)

    Bolhar, R.; Hergt, J.; Woodhead, J.

    1999-01-01

    compositionally similar volcanic greenstones in the Superior Province (Canada). However, this concept is problematic for two reasons: (1) Modern oceanic crust is typically associated with overlying terrigenous/ pelagic sediments, both of which are introduced into the mantle via subduction. Mixing with mantle and subsequent partial melting invariably produces compositions with HFSE depletion and LREE enrichment at low to moderate degrees of melting. (2) Mixing of subduction-modified lithosphere into the mantle followed by melting should be detectable in volcanic rocks with strong depletions in elements such as Nb and Ti, but increased abundances in the LILE and LREE (La/Sm pm >> 1). Compositionally, the Warrawoona meta-igneous rocks resemble compositions found in modern oceanic plateaus (e.g. Broken Ridge) which incorporated variable amounts of continental lithospheric mantle (CLM). Variability in trace element ratios (e.g. Nb/Ta, Ce/Pb, and Nb/U) may reflect source heterogeneity or the coexistence of tectonically accreted oceanic fragments with differing petrogenetic histories. However, well-defined co-variations in major and trace elements of samples from all three major stratigraphic units point to a common magmatic origin. In an attempt to link Archaean rocks to present day analogues, we conclude that the spatial association of ultramafic and mafic volcanics and crustally contaminated high-Mg, Fe rocks most resembles melting of a plume head with incorporation of CLM-components and volcanic outpouring within a (rifted?) continental environment. Support for the existence of pre-existing continental crust comes from published studies which report on xenocrystic zircons in basalts, underlying granitoids and sediments of pre-Warrawoona age and mafic inclusions within granitoid bodies. Temporal decreases in La/Sm pm and Nb/Th pm ratios, along with unfractionated HREE may be interpreted as adiabatic upwelling of plume material and a decreasing influence of the lithospheric component

  16. Implicações biogeográficas de novos registros ornitológicos em um enclave de vegetação de campina no sudoeste da Amazônia brasileira Biogeographic implications of new avian records from a patch of white-sand forest in southwestern Brazilian Amazonia

    Directory of Open Access Journals (Sweden)

    Fabíola Poletto

    2005-12-01

    Full Text Available Campinas constituem um tipo florestal de porte arbóreo reduzido e aspecto geral aberto, que cresce em solos arenosos e lixiviados de toda a Amazônia; apesar de sua ampla distribuição, campinas ocorrem predominantemente nas regiões do alto e médio rio Negro, no noroeste do Amazonas e sul de Roraima, incluindo também o sul da Venezuela e o sudeste da Colômbia. Existem pequenas manchas isoladas de campinas no sudoeste da Amazônia brasileira que ainda não foram estudadas sistematicamente por ornitólogos; portanto, são reportados aqui alguns resultados importantes obtidos durante uma expedição ornitológica a uma mancha de campina no extremo sudoeste do estado do Amazonas (7º22'33,2"S e 73º00'42,5"W. Foram documentados para região os primeiros registros das seguintes espécies: Hemitriccus striaticollis (Lafresnaye, 1853 (Aves, Tyrannidae e Xenopipo atronitens Cabanis, 1847 (Aves, Pipridae; adicionalmente, foram obtidos registros com as seguintes espécies raras ou de distribuição pouco conhecida no sudoeste da Amazônia: Formicivora grisea (Boddaert, 1783 (Aves, Thamnophilidae, Conopias parvus (Pelzeln, 1868 (Aves, Tyrannidae e Heterocercus linteatus (Strickland, 1850 (Aves, Pipridae. Como verificado em manchas de campina distribuídas por todo o norte do Peru, a avifauna de campina que ocorre no sudoeste da Amazônia brasileira é também altamente influenciada por espécies associadas à região do alto rio Negro. Entretanto, uma segunda influência biogeográfica também pôde ser notada: aquela de espécies cujo centro de distribuição está localizado nas campinas do centro e leste da Amazônia, ao sul do rio Amazonas. A avifauna das campinas do sudoeste da Amazônia ainda é pouco conhecida; futuros levantamentos de enclaves de campina nesta região podem levar a novas extensões de distribuição e também à descoberta de novos táxons.White-sand forests (WSF hereafter include several types of stunted and open forest

  17. Latest Cretaceous "A2-type" granites in the Sakarya Zone, NE Turkey: Partial melting of mafic lower crust in response to roll-back of Neo-Tethyan oceanic lithosphere

    Science.gov (United States)

    Karsli, Orhan; Aydin, Faruk; Uysal, Ibrahim; Dokuz, Abdurrahman; Kumral, Mustafa; Kandemir, Raif; Budakoglu, Murat; Ketenci, Murat

    2018-03-01

    An integrated study of comprehensive geochronological, geochemical, and Sr-Nd-Hf isotopic data was undertaken for the A-type Topcam pluton that intruded within the Sakarya Zone (NE Turkey) with the aims of elucidating its origin and tectonic significance and gaining new insights into the generation of aluminous A-type granites. New LA-ICP-MS zircon U-Pb crystallization ages of 72 and 73 Ma indicate emplacement in the Late Cretaceous time, just after extensive metaluminous I-type magmatism in the area. The pluton consists mainly of alkali feldspar, quartz, plagioclase, amphibole, and biotite with accessory minerals such as magnetite, apatite, and zircon. The outcrop is composed of granite, syenite, monzonite, and quartz monzonite and possesses a wide range of SiO2 content (57-70 wt%) with elevated Ga/Al ratios and low Mg# (mostly negative Eu (Eu/Eu* = 0.31 to 0.86) anomalies on the chondrite-normalized REE diagram. The rocks are enriched in some large ion lithophile elements (e.g., Rb, Th and Ba), and spidergrams show a relative depletion in Nb, Ti, and Sr. The granitic rocks of the pluton have identical 87Sr/86Sr(i) ratios ranging from 0.70518 to 0.70716, relatively low εNd (t) values varying from - 5.5 to - 0.4, and TDM ages (0.82-1.19 Ga). In situ zircon analyses show that the rocks have variable negative and positive εHf (t) values (- 5.5 to 5.9) and Hf two-stage model ages (742 to 1468 Ma), which are indicative of minor addition of juvenile material. Sr-Nd isotope modelling suggests mixing of 70-90% of lower crustal-derived melt with 10-30% of mantle-derived melt at lower crust depths. The heat source for partial melting is provided by upwelling of hot asthenosphere triggered by slab roll-back events. Geochemical and isotopic data reveal that metaluminous A2-type granites were derived from partial melting of the Paleozoic lower continental crust dominated by mafic rocks in amphibolitic composition, with minor input of subcontinental lithospheric mantle

  18. Isotopic disequilibrium among commingled hybrid magmas: Evidence for a two-stage magma mixing-commingling process in the Mt. Perkins Pluton, Arizona

    International Nuclear Information System (INIS)

    Metcalf, R.V.; Smith, E.I.; Reed, R.C.

    1995-01-01

    The syn-extensional Miocene Mt. Perkins pluton, northwestern Arizona, cooled rapidly due to its small size (6 km 2 ) and shallow emplacement (7.5 km) and allows examination of commingled rocks that experienced little isotopic exchange. Within the pluton, quartz dioritic to granodioritic host rocks (58-68 wt% SiO 2 ) enclose dioritic enclaves (50-55 wt% SiO 2 ) and a portion contains enclave-free granodiorite (70-74 wt% SiO 2 ). Fine-grained, crenulate enclave margins and a lack of advanced mixing structures (e.g., schlieren, flow fabrics, etc.) indicate an incipient stage of commingling. Isotopic variation between enclaves and enclosing host rocks is large (6.8 to 10.6 ε Nd units; 0.0036 to 0.0046 87 Sr/ 86 Sr units), suggesting isotopic disequilibrium. Comparison of an enclave core and rim suggests that isotopic exchange with the host magma was limited to the enclave rim. Enclaves and hosts collectively form a calc-alkaline suite exhibiting a large range of ε Nd (+1.2 to -12.5) and initial 87 Sr/ 86 Sr (0.705 to 0.71267) with a correlation among ε Nd , initial 87 Sr/ 86 Sr, and major and trace element compositions. Modeling suggests that the suite formed by magma hybridization involving magma mixing accompanied by fractional crystallization. The magma mixing must have predated commingling at the present exposure level and indicates a larger mixing chamber at depth. Isotopic and trace element data suggests mixing end-members were asthenospheric mantle-derived mafic and crustal-derived felsic magmas. Fractional crystallization facilitated mixing by reducing the rheological contrasts between the mafic and felsic mixing end-members. 58 refs., 11 figs., 3 tabs

  19. Some additional observations on inclusions in the granitic rocks of the Sierra Nevada

    Science.gov (United States)

    Dodge, F.C.W.; Kistler, R.W.

    1990-01-01

    Microgranular quartz diorite and diorite inclusions are widespread in central Sierra Nevada granitoid rocks and are almost exclusively restricted to hornblende-bearing rocks, most commonly felsic tonalites and mafic granodiorites. The Nd-Sm and Rb-Sr systematics indicate that most inclusions were in isotopic equilibrium with enclosing materials at the time of formation. Silica contents of inclusions and granitoids are contiguous, but inclusions generally contain less than, and granitoids more than, 60% SiO2. Ferric oxide and H2O+ trends relative to SiO2 suggests many inclusions formed as concentrations of hydrous mafic minerals. Variation of other major element oxides and trace elements support this inference. Most inclusions represent fragmented crystal accumulations of early-formed, near-liquidus minerals generated from these previously mixed magmas. -from Authors

  20. Efeitos de ciclos de umedecimento e secagem na reorganização da estrutura microgranular de latossolos Effects of wetting and drying cycles on the reorganization of the microgranular structure of latosols

    Directory of Open Access Journals (Sweden)

    J. H. M. Viana

    2004-02-01

    Full Text Available Um experimento foi realizado em casa de vegetação com o objetivo de examinar as modificações provocadas por ciclos de umedecimento e secagem em amostras de Latossolos com diferentes mineralogias, em agregados integrais ou quando destruídos por moagem. Amostras de terra fina seca ao ar foram passadas em peneira de 1,0 mm e subdivididas em grupos: solo integral não moído e solo moído em almofariz e passado em peneira de 0,105 mm. O solo moído foi ainda subdividido em solo moído puro ou adicionado de ácido húmico purificado. Os materiais foram montados em cilindro de alumínio e submetidos a dez ciclos sucessivos de umedecimento e secagem, realizados por ascensão capilar, seguidos por secagem ao ar, com intervalo de sete dias entre cada ciclo. Após o término dos ciclos, os solos foram impregnados com resina de poliéster, montando-se seções finas para microscopia, as quais foram levadas para observação em microscópio ótico e fotografadas. As imagens obtidas foram digitalizadas, analisadas e quantificadas por meio do programa QUANTIPORO, desenvolvido no Departamento de Solos/Universidade Federal de Viçosa. Os resultados mostraram completa modificação na forma e no padrão da estrutura após a aplicação dos ciclos nos tratamentos que sofreram destruição de agregados por moagem. Essas mudanças foram atribuídas a uma reacomodação dos agregados fragmentados com a retração do plasma, que se seguiu ao processo de secagem. Todos os materiais estudados mostraram uma estrutura bem diferente da estrutura primária original destes solos. Não se observou qualquer tendência à reversão da estrutura após os dez ciclos, demonstrando que outros fatores, além dos físico-químicos e mineralógicos, devem ser invocados para explicar a gênese de microagregados em Latossolos.A greenhouse experiment was conducted to examine the structural modifications engendered by wetting-drying cycles in Latosol samples (Oxisols with different mineralogical properties submitted to dry grinding, compared with bulk samples. Air-dried soil samples were sieved through a 1.00 mm sieve and separated in two groups. One was kept as control group and the other ground in a mortar and sieved through a 0.105 mm sieve. This second was also split in two groups, one of which received particulate humic acid treatment. The materials were placed in aluminum columns, subjected to 10 weekly wetting cycles by capillarity followed by air-drying. At the end of the cycles, the samples were impregnated with polyester resin, cut in blocks and thin-sectioned for microscopy analysis. The sections were scrutinized under optical microscope, photographed, and the images digitalized, analyzed, and quantified with the Software QUANTIPORO. After the wetting and drying cycles, important alterations in both shape and structural pattern were observed in the ground samples. These changes were attributed to a re-organization of soil particles during the plasma shrinkage after the drying process. All materials presented a different structural pattern in relation to the original soil structure. No trend for reversion to the original structure was observed after the cycles. This indicates that other factors besides the physical-chemical and mineralogical should be considered to explain the genesis of Latosol microaggregates.

  1. High-Risk Microgranular Acute Promyelocytic Leukemia with a Five-Way Complex Translocation Involving PML-RARA

    Directory of Open Access Journals (Sweden)

    Benjamin Powers

    2015-01-01

    Full Text Available Acute promyelocytic leukemia (APL is classically characterized by chromosomal translocation (15;17, resulting in the PML-RARA fusion protein leading to disease. Here, we present a case of a 50-year-old man who presented with signs and symptoms of acute leukemia with concern for APL. Therapy was immediately initiated with all-trans retinoic acid. The morphology of his leukemic blasts was consistent with the hypogranular variant of APL. Subsequent FISH and cytogenetic analysis revealed a unique translocation involving five chromosomal regions: 9q34, 17q21, 15q24, 12q13, and 15q26.1. Molecular testing demonstrated PML/RARA fusion transcripts. Treatment with conventional chemotherapy was added and he went into a complete remission. Given his elevated white blood cell count at presentation, intrathecal chemotherapy for central nervous system prophylaxis was also given. The patient remains on maintenance therapy and remains in remission. This is the first such report of a 5-way chromosomal translocation leading to APL. Similar to APL with chromosomal translocations other than classical t(15;17 which result in the typical PML-RARA fusion, our patient responded promptly to an ATRA-containing regimen and remains in complete remission.

  2. Petrology of Oligocene Ghaleh Yaghmesh granitoids in the west of Yazd province

    Directory of Open Access Journals (Sweden)

    Bahareh Fazeli

    2017-02-01

    calculation of amphibole minerals by Cameca SX50 microprobe device at the Oklahomacity University (Norman - USA. Results The studied plutonic rocks are dominated by plagioclase, orthoclase, quartz, amphibole (magnesio hornblende and actinolite hornblende, biotite, and pyroxene. Zircon, apatite, sphene, tourmaline and opaque minerals as the common accessory and chlorite, epidote and calcite are the secondary minerals. On the base of petrographic observation as well as mineral-chemistry and geochemical data, the granitoid massif is classified as I-type (magnetite series, calc – alkaline and metaluminous composition. The rocks under discussion are characterized by the high level of LILE (Ba, Sr, K and Cs and the negative anomaly of HFS elements (Ti, Nb, Zr and Y indicating the subduction related magmatism. The Ghaleh Yaghmesh granitoids are cogenetic and possibly developed in subduction zone related to active continental margin calc – alkaline volcanic arcs. Mixing process of acidic and basic magmas is likely involved in generation of the rocks being studied. Discussion The parent magma probably formed by partial melting of amphibolites with some sedimentary materials. Fractional crystallization of melt in the higher levels of crust gave rise to various rock types. Mantle – derived basaltic magmas emplaced into the lower crust most likely provide heat for partial melting Clemens et al., 2011(. Field evidences such as the presence of mafic microgranular enclaves having sharp boundaries with the host rocks (Zorpi et al., 1989; Didier, 1991, petrographic observations (similar mineralogy of MME and the host rock (Didier, 1991; Didier and Barbarin, 1991, the occurrence of accicular apatite (Zorpi et al., 1989; Didier, 1991, the corroded margin of amphibole and plagioclase (Zorpi et al., 1989; Shelley, 1993 and the abundance of biotite and hornblende in MME compared to the host rock (Ellis and Thompson, 1986 and geochemical criteria (range of silica from 51.35 to 70.78 indicate

  3. Petrological and geochemical studies of ultramafic–mafic rocks from ...

    Indian Academy of Sciences (India)

    rocks from the North Puruliya Shear Zone (eastern India). Aditi Mandal∗ ..... quently replaced by hornblende along margin and are greater in ...... tion and accumulation. ..... J. Petrol. 43(2) 219–241. Das D K 1977 A review on sulphide zone around Belamu hill, ... implication for trans-continental Gondwanaland correla-.

  4. Petrology, geochemistry and tectonic settings of the mafic dikes and ...

    Indian Academy of Sciences (India)

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

    margins of the basin, whereas, others are aligned .... areas of mantle upwelling, igneous intrusions, deep ... to and during the sedimentary accumulation, and ...... The development of continental margins in plate tectonic theory; J. Aust. Petrol.

  5. Interaction of coeval felsic and mafic magmas from the Kanker ...

    Indian Academy of Sciences (India)

    R Elangovan

    2017-10-05

    Oct 5, 2017 ... relationship with the Sonakhan greenstone belt. In this study, we ... Field relationships and petrography ... fractures of the porphyritic granite (figures 3e and 4c). ..... geochronology of the Precambrians of Bhandara–Drug,.

  6. Mafic rocks from Erinpura gneiss terrane in the Sirohi region ...

    Indian Academy of Sciences (India)

    1Department of Geology, University of Rajasthan, Jaipur 302 004, India. 2GeoZentrum .... from massive to foliated types wherein the gener- ally steep foliations show ... ered for kinematic analyses of the shear movement. These features are ...

  7. Geochemistry and Petrogenesis of Biabanak–Bafq Mafic Mgmatism ...

    Indian Academy of Sciences (India)

    59

    13185-1494. Email: m_poshtkoohi@yahoo.com; Mobile No: +98 912 209 39 73 ...... petrologie et tectonique du precambrien et de sa couverture, Ph.D. thesis, universite ..... Applications of the 190Pt–186OS isotope system to geochemistry and.

  8. Geochemistry and geochronology of the mafic dikes in the Taipusi ...

    Indian Academy of Sciences (India)

    25

    several large linear faults as dividing lines (Fig. 1b; Jahn ... activity between Bainaimiao city and Chifeng city (Stampfli and Borel, 2002). The formation ... In addition, previous studies in the area paid more attention to the geochemistry and.

  9. Eruptive history of Mammoth Mountain and its mafic periphery, California

    Science.gov (United States)

    Hildreth, Wes; Fierstein, Judy

    2016-07-13

    This report and accompanying geologic map portray the eruptive history of Mammoth Mountain and a surrounding array of contemporaneous volcanic units that erupted in its near periphery. The moderately alkaline Mammoth eruptive suite, basaltic to rhyodacitic, represents a discrete new magmatic system, less than 250,000 years old, that followed decline of the subalkaline rhyolitic system active beneath adjacent Long Valley Caldera since 2.2 Ma (Hildreth, 2004). The scattered vent array of the Mammoth system, 10 by 20 km wide, is unrelated to the rangefront fault zone, and its broad nonlinear footprint ignores both Long Valley Caldera and the younger Mono-Inyo rangefront vent alignment.

  10. Depositional features and stratigraphic sections in granitic plutons: implications for the emplacement and crystallization of granitic magma

    Science.gov (United States)

    Wiebe, R. A.; Collins, W. J.

    1998-09-01

    Many granitic plutons contain sheet-like masses of dioritic to gabbroic rocks or swarms of mafic to intermediate enclaves which represent the input of higher temperature, more mafic magma during crystallization of the granitic plutons. Small-scale structures associated with these bodies (e.g. load-cast and compaction features, silicic pipes extending from granitic layers into adjacent gabbroic sheets) indicate that the sheets and enclave swarms were deposited on a floor of the magma chamber (on granitic crystal mush and beneath crystal-poor magma) while the mafic magma was incompletely crystallized. These structures indicate 'way up', typically toward the interior of the intrusions, and appear to indicate that packages of mafic sheets and enclave concentrations in these plutons are a record of sequential deposition. Hence, these plutons preserve a stratigraphic history of events involved in the construction (filling, replenishment) and crystallization of the magma chamber. The distinctive features of these depositional portions of plutons allow them to be distinguished from sheeted intrusions, which usually preserve mutual intrusive contacts and 'dike-sill' relations of different magma types. The considerable thickness of material that can be interpreted as depositional, and the evidence for replenishment, suggest that magma chamber volumes at any one time were probably much less than the final size of the pluton. Thus, magma chambers may be constructed much more slowly than presently envisaged. The present steep attitudes of these structures in many plutons may have developed gradually as the floor of the chamber (along with the underlying solidified granite and country rock) sank during continuing episodes of magma chamber replenishment. These internal magmatic structures support recent suggestions that the room problem for granites could be largely accommodated by downward movement of country rock beneath the magma chamber.

  11. Spain and Morocco: The Spanish Enclaves in North Africa, Potential Mediterranean Security Dilemma

    Science.gov (United States)

    1982-12-01

    continued attempts to depoliticize the military, especially the Army. A major difference in Spain from the 1975 period is the rise of the Socialists...to happenings across the Strait in the towns around Algeciras day. Especially Diario de Ceuta gave the impression of close contact between southern...2,000, with 51 teachers; middle school (E.G.B., Educacion General Basica, *Discussion of this area of potential cooperation between the two countries is

  12. Living and working in ethnic enclaves: English Language proficiency of immigrants in US metropolitan areas

    NARCIS (Netherlands)

    Beckhusen, J.; Florax, R.J.G.M.; de Graaff, T.; Poot, H.J.; Waldorf, B.S.

    2013-01-01

    We use data on Mexican and Chinese immigrants in the US to calculate the average marginal effects of residential and occupational segregation on immigrants' ability to speak English, and similarly the effects of English fluency of family members. Our results confirm that residential segregation is

  13. OEdème aigue du poumon en rapport avec un myxome enclavé ...

    African Journals Online (AJOL)

    threatening depending on their location. We report the case of a 70 years old female patient, enrolled in our training program for the management of respiratory distress associated with acute hemodynamic pulmonary edema. Echocardiography ...

  14. Erotic Enclaves and Contested Beds: Gardens in Pu Songling’s Chuanqi Tales

    Directory of Open Access Journals (Sweden)

    Lei Jin

    2015-02-01

    Full Text Available Abstract:             This article examines the literary garden depicted by Pu Songling (1640-1715 in his' Liaozhai zhiyi '聊齋誌異 (Liaozhai's records of the strange; 1766. These enchanted, deserted, and haunted gardens function as metaphors for the contested ground on which some key Ming-Qing intellectual issues are debated. The article examines Pu’s depiction of 'qing'情,an important concept reflecting the philosophical and literary trends of the time, and shows that in the process of constructing literary gardens, Pu challenges the intellectual issues of his time and dissolves the boundaries between normal and abnormal, reality and ideal, death and life, and order and disorder.

  15. KETAHANAN PANGAN RUMAH TANGGA PETANI SAWAH DI WILAYAH Enclave TAMAN NASIONAL BUKIT BARISAN SELATAN

    Directory of Open Access Journals (Sweden)

    . Amirian

    2012-03-01

    Full Text Available 800x600 Normal 0 false false false IN X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri","sans-serif"; mso-bidi-font-family:"Times New Roman";} The aim of this research was to know the food security of farmer household, based on the availibility of staple food, access to food and  utilization of food of farmer household. The research design was cross-sectional study. The samples were consisted of 35 owner farmer, 12 yeoman, and 13 farmworker. Primary and secondary data was analyzed by Microsoft Excel and SPSS version 13 for windows. The result showed that 48.33% of husband and 78.33% of wife were 40 years old. As many as 66.67% of husband education and 70.00% of wife education were elementary school.  Most of the sample were farmers, 26.67% husband and 18.33% wife had additional work. The result showed, based on the availability of staple food, 70.00% of household catagorized as food secured. Based on the access to food, 65.00% of household catagorized as food secured, and based on the utilization of food, 56.70% of household catagorized as food secured. The conclusion of this research, 63.30% of household catagorized as food secured based on combination of three component of food security. There was a significant positive correlation (pproduction distributed to household with the availability of energy per capita per day. Key words: food security, household

  16. COMMUNITY DETERMINANTS OF IMMIGRANT SELF-EMPLOYMENT: HUMAN CAPITAL SPILLOVERS AND ETHNIC ENCLAVES

    OpenAIRE

    Liliana Sousa

    2013-01-01

    I find evidence that human capital spillovers have positive effects on the proclivity of low human capital immigrants to self-employ. Human capital spillovers within an ethnic community can increase the self-employment propensity of its members by decreasing the costs associated with starting and running a business (especially, transaction costs and information costs). Immigrants who do not speak English and those with little formal education are more likely to be self-employed if they reside...

  17. Hydrocarbon-Rich Territories in Central Asia: Producing Countries, Exporting Enclaves or Transit Countries?

    Directory of Open Access Journals (Sweden)

    Aurelia Mañé

    2005-10-01

    Full Text Available This article aims to qualify the different analyses and currents of opinion that are circulating with respect to Central Asia’s capacity to become one of the main exporters of hydrocarbons in the next decade. For this, it first examines whether or not, in quantitativeterms, the hydrocarbon-rich territories of Central Asia can become one of the main suppliers on a world scale; secondly, it explains why the countries of Central Asia will play a necessarily different role on the international energy scene than that played by the OPEC countries; and, finally, it indicates what the relevance of this area could be in the organisation (structure of the contemporary international energy scene. In this sense, it discusses not producing countries, but rather countries of passage.

  18. Territorialisation et enclaves littorales dans les îles de la Caraïbe

    Directory of Open Access Journals (Sweden)

    Michel Desse

    2008-04-01

    Full Text Available Les littoraux de la Caraïbe ont longtemps été considérés comme des espaces de l’envers, ouverts, libres, propriété de l’Etat donc de tous, opposables à la plantation qui hiérarchise la société, structure le paysage et identifie la richesse.Aujourd’hui, les littoraux constituent les centres fonctionnels des îles, annexés parfois privatisés, ils apparaissent fortement territorialisés. Les facteurs qui expliquent ces transformations sont multiples. Les îles connaissent une forte tertiairisation ...

  19. Megadesarrollos turísticos de sol y playa enclaves del imaginario

    OpenAIRE

    Rodríguez González, Sylvia Cristina

    2009-01-01

    Los megadesarrollos turísticos de sol y playa han sido impulsados por el Banco Interamericano de Desarrollo (BID) como proyectos de estrategia de desarrollo turístico, en México nacen los Centros Integralmente Planeados (CIP´s) para dar orden urbano, descentralizando grandes inversiones turísticas principalmente de origen extranjeros. Son identificados ante la promoción turística por la inversión de insumos y tecnología. Los emplazamientos turísticos de sol y playa han crecido y destina...

  20. Ghettos and enclaves in the cross-place realm: mapping socially bounded spaces across cities.

    Science.gov (United States)

    Montgomery, Alesia F

    2011-01-01

    Since the early Chicago School, urban researchers have used residential proximity to assess contacts within and between racial and ethnic groups. This approach is increasingly limited. Diverse groups use email, social networking sites, instant messaging and mobile phones to communicate across urban zones and distant cities. These practices enable mutual support among far-flung family members and co-ethnics as they engage with an array of institutions throughout their day. Through interviews and observations that include women and men of diverse occupations, races and national origins, the author explores how and why cross-place enclosures of sociality and resources develop. Rather than framing the residential area as the locus of racial/ethnic concentration, the author focuses on cross-place concentrations in the technologically mediated workspace. This study enhances theorization of the structural negotiations, interpersonal pressures and group preferences that produce separate lifeworlds in globalizing cities.

  1. Strong Ties, Weak Ties, and Human Capital: Latino Immigrant Employment outside the Enclave

    Science.gov (United States)

    Pfeffer, Max J.; Parra, Pilar A.

    2009-01-01

    This study focuses on the role of social ties and human capital in the integration of Latino immigrants into the local economy. This analysis extends earlier research by focusing on more rural contexts with limited labor-market opportunities and less access to social resources provided by coethnics. We reconsider conclusions of previous studies by…

  2. Enclaves agrícolas modernos: el caso del jitomate mexicano en los mercados internacionales

    Directory of Open Access Journals (Sweden)

    Alejandro Macías

    2003-01-01

    las nuevas exigencias de la producción flexible. Entre dichas características podemos considerar las siguientes: la creciente participación en el mercado de productos frescos de Estados Unidos, pero también la elevada concentración en dicho mercado y en ese tipo de oferta, sin existir mayor valor agregado; la dependencia externa que se tiene sobre la provisión de insumos y medios de producción, que hacen que esta industria quede supeditada a las decisiones estratégicas tomadas en el país consumidor. Así, también se destacan los procesos de integración económica entre los dos países surgidos de la conformación del bloque comercial de Norteamérica, donde no sólo hay relaciones de competencia entre las naciones sino también de complementariedad.

  3. Do Ethnic Enclaves Impede Immigrants’ Integration? Evidence from a Quasi-Experimental Social-Interaction Approach

    OpenAIRE

    Danzer, A. M.; Yaman, F.

    2013-01-01

    It is widely debated whether immigrants who live among co-ethnics are less willing to integrate into the host society. Exploiting the quasi-experimental guest worker placement across German regions during the 1960/70s as well as information on immigrants’ inter-ethnic contact networks and social activities, we are able to identify the causal effect of ethnic concentration on social integration. The exogenous placement of immigrants "switches off" observable and unobservable differences in t...

  4. Federal enclaves: The community culture of Department of Energy cities Livermore, Los Alamos, Oak Ridge

    Science.gov (United States)

    Moore, Patrick Kerry

    During the Second World War, the United States Government funded the research of nuclear fusion to create the first atomic weapons. To accomplish this task, the Manhattan Engineering District recruited scientists and engineers to remote sites in New Mexico, Tennessee, and Washington. During the five decades of the Cold War, the congressionally created Atomic Energy Commission, and later the Department of Energy (DOE), funded and operated numerous facilities throughout the United States. The mission of the facilities was to design and stockpile atomic weapons and to further the understanding of nuclear energy. This dissertation examines the influences of the United States federal government on three communities associated with these facilities, Los Alamos, New Mexico, Oak Ridge, Tennessee, and Livermore, California. As isolated secret cities, these environments each created complex community structures. This work identifies how, unlike other community settings, the influences of the federal government, both directly and indirectly, created distinctive patterns of behavior within the residents of each city. Examining these behaviors within the framework of the dissertation's chapters provides the necessary context to understand fully the community culture of these Department of Energy cities. This work addresses contemporary community settings in new ways. It approaches the topic broadly by examining five specific areas of community interaction: social, political, business and economic, educational, and ethical. Through the use of oral history methodology and techniques, the researcher captured significant information from respondents. This approach provides valuable insights to the behavior and interaction of the individual populations while revealing important insights all aspects of each town's community culture.

  5. A prolonged granitoid formation in Saglek Block, Labrador: Zonal growth and crustal reworking of continental crust in the Eoarchean

    Directory of Open Access Journals (Sweden)

    Tsuyoshi Komiya

    2017-03-01

    We made a detailed sketch of a small outcrop in St. John's Harbour South (SJHS area, and classified the orthogneisses and mafic enclaves into seven generations based on the geologic occurrence. The first and second generations comprise mafic rocks and lack magmatic zircons. We conducted CL imaging and U-Pb dating of zircons from the third, sixth and seventh generation of the orthogneisses to estimate the protolith ages at 3902 ± 25, 3892 ± 33 and 3897 ± 33 Ma for each, supporting the presence of the over 3.9 Ga Iqaluk Gneiss. The geological occurrence that the mafic rocks occur as enclaves within the 3.9 Ga Iqaluk Gneiss indicates that they are the oldest supracrustal rocks in the world. Our geochronological and geological studies show the Uivak Gneiss is quite varied in lithology and age from 3.6 to >3.9 Ga, and tentatively classified into six groups based on their ages. The oldest Uivak Gneiss components including the Iqaluk Gneiss are present around the SJHS area, and the orthogneisses become young as it is away. The lines of evidence of overprinting of younger granitoid on older granitoid in small outcrops and geological-map scale as well as presence of inherited zircons even in the oldest suite suggests that crustal reworking played an important role on erasing the ancient crusts.

  6. Petrology of the Porriño late-Variscan pluton from NW Iberia. A model for post-tectonic plutons in collisional settings

    Energy Technology Data Exchange (ETDEWEB)

    González Menéndez, L.; Gallastegui, G.; Cuesta, A.; Montero, P.; Rubio-Ordoñez, A.; Molina, J.F.; Bea, F.

    2017-07-01

    The Variscan orogen of NW Iberia contains abundant syn- and post-tectonic granitoids. The post-tectonic granitoids are metaluminous to slightly peraluminous, I-type granites, monzogranites ± granodiorites ± tonalites. The Porriño pluton studied here is a representative example. It consists of two units: i) a pink-red, peraluminous, biotite granite and ii) a gray, metaluminous to peraluminous, biotite (± amphibole ± titanite) monzogranite, including maficintermediate enclaves. SHRIMP U-Pb dating yielded 290-295Ma ages for all the units. The mineralogy and geochemistry show that the pink-red granite has features of I- and A-type granites, whereas the gray monzogranite and enclaves are I-types. Sr isotopes show scattered values for the pink-red granite (87Sr/86Sr295Ma ≈ 0.702-0.710) and uniform values for the gray monzogranite and enclaves (87Sr/86Sr295Ma≈ 0.705-0.706). Geochemical results indicate a peritectic entrainment of clinopyroxene + orthopyroxene ± Ca-plagioclase ± ilmenite ± garnet, and minor accessory phases (± zircon ± titanite ± apatite) into a melt similar to the leucocratic gray monzogranite. A mafic-intermediate source is proposed for the gray monzogranite and its enclaves. Restitic protoliths generated granitic melts with A-type features such as the pink-red granite. The I-type nature of many post-tectonic granitoids could be explained by the previous extraction of S-type syn-tectonic granites that left restites and less fertile rocks. Late orogenic new melting affected the previously unmelted and more mafic lithologies of the lower-middle crust, and gave rise to I-type granitoids. Repeated melting events affecting such lithologies and previous restites could have generated granitic melts with A-type features.

  7. Raman study of the repair of surgical bone defects grafted with biphasic synthetic microgranular HA + β-calcium triphosphate and irradiated or not with λ780 nm laser.

    Science.gov (United States)

    Soares, Luiz Guilherme P; Marques, Aparecida Maria C; Barbosa, Artur Felipe S; Santos, Nicole R; Aciole, Jouber Mateus S; Souza, Caroline Mathias C; Pinheiro, Antonio Luiz B; Silveira, Landulfo

    2014-09-01

    The treatment of bone loss due to different etiologic factors is difficult, and many techniques aim to improve repair, including a wide range of biomaterials and, recently, photobioengineering. This work aimed to assess, through Raman spectroscopy, the level of bone mineralization using the intensities of the Raman peaks of both inorganic (∼ 960, ∼ 1,070, and ∼ 1,077 cm(-1)) and organic (∼ 1,454 and ∼ 1,666 cm(-1)) contents of bone tissue. Forty rats were divided into four groups each subdivided into two subgroups according to the time of killing (15 and 30 days). Surgical bone defects were made on femur of each animal with a trephine drill. On animals of group Clot, the defect was filled only by blood clot; on group Laser, the defect filled with the clot was further irradiated. On animals of groups Biomaterial and Laser + Biomaterial, the defect was filled by biomaterial and the last one was further irradiated (λ780 nm, 70 mW, Φ ∼ 0.4 cm(2), 20 J/cm(2) session, 140 J/cm(2) treatment) in four points around the defect at 48-h intervals and repeated for 2 weeks. At both 15th and 30th day following killing, samples were taken and analyzed by Raman spectroscopy. At the end of the experimental time, the intensities of both inorganic and organic contents were higher on group Laser + Biomaterial. It is concluded that the use of laser phototherapy associated to biomaterial was effective in improving bone healing on bone defects as a result of the increasing deposition of calcium hydroxyapatite measured by Raman spectroscopy.

  8. Sienogranitos leucocráticos do Domínio Macururé, Sistema Orogênico Sergipano, Nordeste do Brasil: Stock Glória Sul

    Directory of Open Access Journals (Sweden)

    Joane Almeida da Conceição

    Full Text Available RESUMO: O Stock Glória Sul (SGS (41 km2 é arredondado e intrusivo na parte central do Domínio Macururé, no Sistema Orogênico Sergipano (SOS. Internamente o Stock é formado por vários tipos de sienogranitos leucocráticos (biotita sienogranito, sienogranito com muscovita e biotita e muscovita sienogranito. Os biotita sienogranitos apresentam abundância de enclaves máficos microgranulares que correspondem a sienitos e são ocasionais nos sienogranitos com muscovita e biotita. Os sienogranitos são metaluminosos, com termos mais evoluídos peraluminosos, posicionando-se no campo dos granitos do tipo I e exibem assinatura geoquímica cálcio-alcalino de alto K2O. Os enclaves sieníticos são metaluminosos e exibem assinatura shoshonítica. Os dados geoquímicos sugerem que as diferentes rochas presentes no SGS podem ser explicadas como produto da mistura entre um magma fortemente diferenciado e peraluminoso (≈ 73% SiO2 com outro máfico shoshonítico (≈ 56% SiO2, representado pelos enclaves. Os valores dos elementos traços são mais elevados nos enclaves do que nos granitos, tais como Ba (1.179 - 319 ppm, Rb (351 - 55,3 ppm, Y (16,7 - 1,6 ppm. Os padrões de elementos terras raras mostram variação de ∑38,58 - 299,21 ppm, LaN/YbN 12,57 - 137,22 e Eu/Eu* 0,72 - 1,94. O SGS, ante aos resultados obtidos neste estudo, evidencia que a granitogênese no Domínio Macururé (DM é complexa e que os sienogranitos leucocráticos que ocorrem bem distribuídos nesse domínio são pós-tectônicos e representam o produto de interação entre magmas riolíticos peraluminosos com magmas mantélicos shoshoníticos.

  9. Coexistence and mixing of magmas in the late precambrian Itaporanga batholith, State of Paraiba, Northeastern Brazil

    International Nuclear Information System (INIS)

    Mariano, G.; Sial, A.N.

    1990-01-01

    The Precambrian Cachoeirinha-Salgueiro Fold Belt (CSF) located in the western portion of the states of Pernambuco and Paraiba is intruded, in its northern portion, by several coarsely porphyritic potassic calc-alkalic batholiths. These batholiths were syntectonically emplaced in relation to the Brasiliano cycle (=Pan-African) and are commonly associated with potassium diorites suggesting coexistence and mixing between felsic and mafic magmas. In the Itaporanga batholith three petrographic domains were mapped. A hybrid zone characterized by intense mechanical mixing of granite to granodiorite and potassium diorite magmas is located towards the border of the batholith. A commingling zone where felsic porphyritic granite to granodiorite and potassium diorite rocks are individualized at outcrop scale is located towards the center of the batholith. Finally a felsic porphyritic facies occur in the hybrid zone. Similarity among chemical analyses of amphiboles from potassium dioritic enclaves of the Itaporanga batholith and from the potassium diorite stock east of it suggest a common source for both magmas. This hypothesis is corroborated by similar REE patterns for potassium dioritic enclaves of the Itaporanga batholith and for the potassium diorite stock. The batholith shows a well developed foliation which dips towards its core suggesting that the present level of exposure represents the root zone of a diapir, where intense interaction between felsic and mafic magmas took place. (author)

  10. El espacio turístico, entre el enclave y el derrame: estudio en dos barrios de Buenos Aires

    Directory of Open Access Journals (Sweden)

    Mercedes González Bracco

    2017-01-01

    Full Text Available Este trabajo problematiza la idea de “espacio turístico” al proponer entenderlo no como un dato cartográfico sino -partiendo de una mirada antropológica- como producto de las prácticas que se realizan en él. Para ello tomamos dos barrios de la ciudad de Buenos Aires como estudios de caso: La Boca y Palermo, diferentes en su historia, paisaje y composición demográfica, pero igualados por su interés turístico. La metodología desarrollada incluyó estrategias etnográficas, análisis de prensa y referentes virtuales. A partir del trabajo de campo se observó cómo los discursos y prácticas sobre estos barrios modelan espacios turísticos diferentes, tanto en términos de la propuesta como del uso y sentidos otorgados por parte de los turistas.

  11. Emerging Voices: "Speak White": Language Policy, Immigration Discourse, and Tactical Authenticity in a French Enclave in New England

    Science.gov (United States)

    Peters, Jason

    2013-01-01

    This article provides a historical case study of the Sentinelle Affair, a conflict between French language rights and the English Only educational policies of the Catholic Church in New England in the 1920s. An analysis of this conflict reveals a correspondence between programs of language centralization and the production of language differences…

  12. The diversity of languages in the Alpine-Adriatic region I. Linguistic minorities and enclaves in northern Italy

    Directory of Open Access Journals (Sweden)

    Herta Maurer-Lausegger

    2004-05-01

    Full Text Available Der im vorliegenden Beitrag präsentierte multinationale Sprachraum des Alpen-Adria Gebiets stellt zweifelsohne eines der interessantesten und vielfältigsten Kulturräume Europas dar. Durch die jahrhundertelange Symbiose slawischer, germanischer und romanischer Kultur und die bewegte historische Vergangenheit hat sich in diesen Gebieten und Regionen sukzessive eine komplexe Verflechtung von Sprachen, Varietäten, Dialekten und Mundarten entwickelt, die in vielfältigster Weise und in unterschiedlichem Ausmass aufeinander wirken. Die soziolinguistische Situation in diesen multiethnischen Gebieten ist komplex und weist regionsspezifische Besonderheiten auf, die sich in unterschiedlichster Weise manifestieren. Einige mundartliche Existenzformen des Alpen-Adria-Gebiets sind bereits verschwunden, viele sind vom Aussterben bedroht. Der Bewahrung der am Alpenhauptkamm Norditaliens angesiedelten vielfältigen Mundarten, Dialekte und Varietäten, aber auch der Pflege der kulturellen Identität ethnischer Minderheiten wird zurzeit überall verstärkt Beachtung geschenkt. Ob und in welcher Form hier die Sprachen-, Dialekt- und Varietätenvielfalt bewahrt werden kann, wird wohl von den jeweiligen sprachpolitischen, sozioökonomischen, ethnopsychologischen, rechtlichen u. a. Faktoren abhängig sein. Die Sprachenvielfalt des Alpen-Adria-Gebiets stellt für das multikulturelle Europa der Regionen zweifellos eine außerordentliche Bereicherung dar.

  13. The diversity of languages in the Alpine-Adriatic region I. Linguistic minorities and enclaves in northern Italy

    Directory of Open Access Journals (Sweden)

    Herta Maurer-Lausegger

    2003-05-01

    Full Text Available Der im vorliegenden Beitrag präsentierte multinationale Sprachraum des Alpen-Adria Gebiets stellt zweifelsohne eines der interessantesten und vielfältigsten Kulturräume Europas dar. Durch die jahrhundertelange Symbiose slawischer, germanischer und romanischer Kultur und die bewegte historische Vergangenheit hat sich in diesen Gebieten und Regionen sukzessive eine komplexe Verflechtung von Sprachen, Varietäten, Dialekten und Mundarten entwickelt, die in vielfältigster Weise und in unterschiedlichem Ausmass aufeinander wirken. Die soziolinguistische Situation in diesen multiethnischen Gebieten ist komplex und weist regionsspezifische Besonderheiten auf, die sich in unterschiedlichster Weise manifestieren. Einige mundartliche Existenzformen des Alpen-Adria-Gebiets sind bereits verschwunden, viele sind vom Aussterben bedroht. Der Bewahrung der am Alpenhauptkamm Norditaliens angesiedelten vielfältigen Mundarten, Dialekte und Varietäten, aber auch der Pflege der kulturellen Identität ethnischer Minderheiten wird zurzeit überall verstärkt Beachtung geschenkt. Ob und in welcher Form hier die Sprachen-, Dialekt- und Varietätenvielfalt bewahrt werden kann, wird wohl von den jeweiligen sprachpolitischen, sozioökonomischen, ethnopsychologischen, rechtlichen u. a. Faktoren abhängig sein. Die Sprachenvielfalt des Alpen-Adria-Gebiets stellt für das multikulturelle Europa der Regionen zweifellos eine außerordentliche Bereicherung dar.

  14. DEL COMPROMISSO POLÍTICO AL COMBATE POR LOS DERECHOS: LOS OBSERVATORIOS DE DERECHOS HUMANOS COMO ENCLAVES TERRITORIALES

    Directory of Open Access Journals (Sweden)

    Cora Escolar

    2008-04-01

    Full Text Available El foco del artículo está puesto en pensar, los alcances del emplazamiento de observatorios de derechos humanos, como política pública. Se trata de enlazar los resultados de esta práctica con las cuestiones que afectan la construcción de sujetos de derecho, al interior de una institución.

  15. Globalization of Malaysian Economy – With Special Focus on the Role of Growth Enclaves

    OpenAIRE

    Khondaker Mizanur Rahman; Rafiuddin Ahmed

    2014-01-01

    This paper examines the process of the globalization of Malaysia, a country that has developed over four decades to become one of the top three globalized nations of Asia, after Singapore and Israel. Initially, its enormous primary resources supplied it with a comparative advantage. It pursued an export-oriented economic policy that attracted multinational company (MNC) foreign direct investment (FDI), and modern technology. Subsequently, industrial products from Malaysia made inroads into wo...

  16. Crystallization Conditions at Cascade and Other Arc Volcanoes: The Role of Recharge, and Ultimate, Proximal and Immediate Causes of Eruption

    Science.gov (United States)

    Putirka, K. D.

    2016-12-01

    A number of hypotheses have been offered to explain why volcanoes erupt. These include magma mixing, mafic recharge, or partial crystallization, any of which can drive parts or all of a system to vapor saturation, and so add to a magma's buoyancy. Age dates indicate long pre-eruption storage times for felsic magmas erupted at arcs, indicating that mafic recharge magmas, which can reinvigorate such systems, is a possible eruption trigger. However, plutonic systems reveal numerous recharge events that have no obvious ties to eruption (Coint et al. 2013; Putirka et al. 2014). And crystallization conditions at some arc systems support the implicit view, that recharge might be a necessary, but not a sufficient condition for eruption. At several Cascade volcanoes, Cpx and Amp crystals record coolings of 100-300oC. The Cpx grains derive exclusively from mafic enclaves, while Amp grains derive from both host and enclave materials. These considerable coolings call for a time lag following recharge, and indicate that vapor saturation is a proximal, although not necessarily an immediate cause of eruption. But we cannot discount recharge altogether. At the Cascades and at other arcs, Cpx crystalizes throughout the middle and upper crust, mostly from the surface down to 15 km. And high Fo olivine grains provide evidence for very hot magmas that intrude the upper mantle and lower crust, and possibly the middle crust, if hydrous. Volcanic pathways thus clearly extend into the middle crust, and at times, well below the Moho. It is unclear to what extent these deep pathways are hydraulically connected to the surface, or the role of deep-seated processes in initiating or sustaining eruptions. Progress in understanding these pathways, and triggering mechanisms, requires our differentiating "ultimate", "proximal" and "immediate" causes, and determining which of various magmatic processes provide necessary or sufficient conditions for eruption.

  17. Separate zones of sulfate and sulfide release from subducted mafic oceanic crust

    Science.gov (United States)

    Tomkins, Andrew G.; Evans, Katy A.

    2015-10-01

    Liberation of fluids during subduction of oceanic crust is thought to transfer sulfur into the overlying sub-arc mantle. However, despite the importance of sulfur cycling through magmatic arcs to climate change, magma oxidation and ore formation, there has been little investigation of the metamorphic reactions responsible for sulfur release from subducting slabs. Here, we investigate the relative stability of anhydrite (CaSO4) and pyrite (FeS2) in subducted basaltic oceanic crust, the largest contributor to the subducted sulfur budget, to place constraints on the processes controlling sulfur release. Our analysis of anhydrite stability at high pressures suggests that this mineral should dominantly dissolve into metamorphic fluids released across the transition from blueschist to eclogite facies (∼450-650 °C), disappearing at lower temperatures on colder geothermal trajectories. In contrast, we suggest that sulfur release via conversion of pyrite to pyrrhotite occurs at temperatures above 750 °C. This higher temperature stability is indicated by the preservation of pyrite-bornite inclusions in coesite-bearing eclogites from the Sulu Belt in China, which reached temperatures of at least 750 °C. Thus, sulfur may be released from subducting slabs in two separate pulses; (1) varying proportions of SO2, HSO4- and H2S are released via anhydrite breakdown at the blueschist-eclogite transition, promoting oxidation of remaining silicates in some domains, and (2) H2S is released via pyrite breakdown well into the eclogite facies, which may in some circumstances coincide with slab melting or supercritical liquid generation driven by influx of serpentinite-derived fluids. These results imply that the metallogenic potential in the sub-arc mantle above the subducting slab varies as a function of subduction depth, having the greatest potential above the blueschist-eclogite transition given the association between oxidised magmas and porphyry Cu(-Au-Mo) deposits. We speculate that this zoned sulfur liberation might be one of the factors that lead to the apparently redox-influenced zoned distribution of ore deposit types in the Andean arc. Furthermore, given the lack of sulfate-associated sea floor oxidation prior to the second great oxidation event, the pattern of sulfur transfer from the slab to the sub-arc mantle likely changed over time, becoming shallower and more oxidised from the Neoproterozoic onwards.

  18. Tectonic implications of the contrasting geochemistry of Damaran mafic volcanic rocks, South West Africa

    International Nuclear Information System (INIS)

    Miller, R.McG.

    1983-01-01

    Ortho-amphibolites occur in the southern and central parts of the north-east-trending branch of the Damara Orogen. The Matchless Member amphibolites are interbedded with quartzose mica schist. Mobility of Si, ΣFe, Mn, Mg, Ca, Na, K, P, CO 2 , H 2 O, Rb, Ba, Sr and possibly LREE and immobility of Co, V, Sc, Ga, Zr, Nb, Y and HREE are indicated during metamorphism and reaction with country rock. Central Zone amphibolites are alkaline. The stratigraphically lower amphibolites have a within-plate chemistry; their distribution and associated rock types indicate a continental origin. The Matchless amphibolites have an ocean-floor chemistry. The Damaran sedimentary and orogenic cycle was initiated by continental rifting in three parallel zones in which alkaline acid volcanics occur locally. Widespread subsidence of the rift zones and the intervening areas followed and led to deposition of carbonate and clastic rocks under shallow marine conditions. During renewed rifting, submarine, alkaline basic lavas were extruded. The Southern Margin Zone amphibolites are interbedded with continental slope mixtites and continental rise deep-water fans. Spreading led to continental breakup and the formation of oceanic crust

  19. Structural control on basaltic dike and sill emplacement, Paiute Ridge mafic intrusion complex, southern Nevada

    International Nuclear Information System (INIS)

    Carter Krogh, K.E.; Valentine, G.A.

    1996-08-01

    Late Miocene basaltic sills and dikes in the Paiute Ridge area of southern nevada show evidence that their emplacement was structurally controlled. Basaltic dikes in this area formed by dilating pre-existing vertical to steeply E-dipping normal faults. Magma propagation along these faults must have required less energy than the creation of a self-propagated fracture at dike tips and the magma pressure must have been greater than the compressive stress perpendicular to the fault surface. N- to NE-trending en echelon dikes formed locally and are not obviously attached to the three main dikes in the area. The en echelon segments are probably pieces of deeper dikes, which are segmented perhaps as a result of a documented rotation of the regional stresses. Alternatively, changes in orientation of principal stresses in the vicinity of each en echelon dike could have resulted from local loads associated with paleotopographic highs or nearby structures. Sills locally branched off some dikes within 300 m of the paleosurface. These subhorizontal bodies occur consistently in the hanging wall block of the dike-injected faults, and intrude Tertiary tuffs near the Paleozoic-Tertiary contact. The authors suggest that the change in stresses near the earth's surface, the material strength of the tuff and paleozoic rocks, and the Paleozoic bedding dip direction probably controlled the location of sill formation and direction of sill propagation. The two largest sills deflected the overlying tuffs to form lopoliths, indicating that the magma pressure exceeded vertical stresses at that location and that the shallow level and large size of the sills allowed interaction with the free (earth's) surface. 32 refs., 4 figs., 1 tab

  20. Somma-Vesuvius Plinian Eruptions fed by mafic magma: insights from bubbles in melt inclusions

    Science.gov (United States)

    Esposito, R.; Redi, D.; Cannatelli, C.; Danyushevsky, L. V.; Lima, A.; Bodnar, R. J.; De Vivo, B.

    2014-12-01

    Mt. Somma-Vesuvius Plinian eruptions were first described by Pliny the younger in 79 AD during the infamous eruption that destroyed Pompeii. Today, such eruptions are still a concern to the nearly 3 million people living in the Naples metropolitan area. Understanding the source for Mt. Somma-Vesuvius magma and the coexisting volatile phase is vital to better constrain the long-term eruptive behavior of this volcano. In the present study, ~ 50 olivine phenocrysts were selected from lavas and pumices produced during mild effusive events referred to as inter-Plinian eruptions, and from highly explosive Plinian eruptions that occurred at Mt. Somma-Vesuvius between 33000 ka and 1631 AD. Selected olivine phenocrysts containing MI were examined petrographically and analyzed for Fo content. Fo varies from 69 to 73 mole% for inter-Plinian olivine crystals and from 84 to 90 mole% with one zoned olivine containing 76-81 mole% Fo, for Plinian olivine crystals. Investigated MI vary from slightly crystallized to highly crystallized. Selected crystallized MI were reheated using the Vernadsky stage, and quenched to a homogeneous glass (Group 1) or glass plus a vapor bubble (Group 2). On one hand, MI of Group 1 are hosted in olivine ranging from Fo72 to Fo76 and were all erupted from the Pompeii eruption (white pumice deposit). On the other hand, MI of Group 2 are trapped in olivine ranging from Fo69 to Fo81 and from Fo84 to Fo90, and the hosts are representative of both Plinian and inter-Plinian events. The only eruption where Group-1 and Group-2 MI coexist is the Pompeii eruption. Group 2 MIs were further analyzed by Raman to test for the presence of volatiles (CO2 or H2O) in the vapor bubbles. CO2 was detected in all MI analyzed. CO2 density was determined using the distance between the two Fermi-diad peaks, and ranges between 0.14 and 0.55 g/cm3. Six MI also showed evidence for H2O in the vapor bubble. In addition, carbonates were detected at the glass-vapor interface of five MI. This study shows that the CO2-rich fluid phase, which might exsolve from Plinian melts contain a significant amount of H2O. In addition, the first melting temperature of the fluids in the vapor bubble (~ -58ºC) suggests that volatile components, other than CO2, are included in the vapor bubbles.

  1. A Late Holocene explosive mafic eruption of Villarrica volcano, Southern Andes: The Chaimilla deposit

    Science.gov (United States)

    Costantini, L.; Pioli, L.; Bonadonna, C.; Clavero, J.; Longchamp, C.

    2011-03-01

    Villarrica (Chile) is one of the most active volcanoes in South America having erupted about 60 times in the last 460 years. Although its historical eruptive activity has been mainly effusive and weakly explosive, it had strong explosive behaviour in postglacial times. Chaimilla (activity. The deposit is dispersed over an area of 250 km 2 and consists of 8 units (A-H) which were grouped into four sequences. Stratigraphic data suggest that the eruption had a relatively short duration and evolved from i) an Opening phase, dispersing ash, lapilli clasts, accretionary lapilli, blocks and bombs, to ii) a Pulsatory phase, originating a series of magmatic explosions, to iii) a Collapsing phase, characterised by unstable plumes which emplaced a series of pyroclastic density currents intercalated with thin fallout layers and finally to iv) a Climactic phase forming a more sustained plume which eventually collapsed generating the final pyroclastic density currents. The deposit (fall and flow) has a minimum cumulative volume of 0.6 km 3, with the main sustained phase being associated with a VEI 4 and the flow units having a minimum estimated total volume of 0.04 km 3. The erupted material has a homogenous chemical composition but displays a remarkable variability in both textural and physical properties. The density distribution of juvenile products shows a clear bimodality characterised by two main populations: P1 and P2. Population P1 consists of highly vesicular clasts (modal density around 1000 kg m - 3 ) with mostly sub-spherical bubbles and moderately crystallised groundmass with large-sized microlites. Clasts from population P2 are poorly vesicular (modal density around 1600 kg m - 3 ) with irregular to collapsed bubbles and numerous smaller microlites. The variability of both vesicularity and microlite characteristics suggests the involvement of two magma batches with distinct pre-eruptive degassing and rising histories. Our eruption conceptual model implies the arrival of new magma (represented in the deposit by P1 clasts) into a small, outgassed magma body which was accumulated at shallow level (mainly represented by P2 clasts). A new Chaimilla-type eruption could significantly affect the communities that have recently developed around Villarrica volcano and subsist mainly on tourism and forestry. As a result, a better understanding of the dynamics and evolution of the Chaimilla eruption is necessary for the identification of potential hazard scenarios at Villarrica volcano and, ultimately, for the risk mitigation of this populated area of Southern Chile.

  2. Geochemical constraints on the evolution of mafic and felsic rocks in ...

    Indian Academy of Sciences (India)

    basalt marks the eruption of these rocks in a subaqueous environment. Intermittent eruption ..... Canary Hill of Hazaribagh town which is believed to retain record of the ... beam current of 10 nA at the Electron Microprobe. Analyzer Laboratory ...

  3. Origin of silicic magmas along the Central American volcanic front: Genetic relationship to mafic melts

    Science.gov (United States)

    Vogel, Thomas A.; Patino, Lina C.; Eaton, Jonathon K.; Valley, John W.; Rose, William I.; Alvarado, Guillermo E.; Viray, Ela L.

    2006-09-01

    Silicic pyroclastic flows and related deposits are abundant along the Central American volcanic front. These silicic magmas erupted through both the non-continental Chorotega block to the southeast and the Paleozoic continental Chortis block to the northwest. The along-arc variations of the silicic deposits with respect to diagnostic trace element ratios (Ba/La, U/Th, Ce/Pb), oxygen isotopes, Nd and Sr isotope ratios mimic the along-arc variation in the basaltic and andesitic lavas. This variation in the lavas has been interpreted to indicate relative contributions from the slab and asthenosphere to the basaltic magmas [Carr, M.J., Feigenson, M.D., Bennett, E.A., 1990. Incompatible element and isotopic evidence for tectonic control of source mixing and melt extraction along the Central American arc. Contributions to Mineralogy and Petrology, 105, 369-380.; Patino, L.C., Carr, M.J. and Feigenson, M.D., 2000. Local and regional variations in Central American arc lavas controlled by variations in subducted sediment input. Contributions to Mineralogy and Petrology, 138 (3), 265-283.]. With respect to along-arc trends in basaltic lavas the largest contribution of slab fluids is in Nicaragua and the smallest input from the slab is in central Costa Rica — similar trends are observed in the silicic pyroclastic deposits. Data from melting experiments of primitive basalts and basaltic andesites demonstrate that it is difficult to produce high K 2O/Na 2O silicic magmas by fractional crystallization or partial melting of low-K 2O/Na 2O sources. However fractional crystallization or partial melting of medium- to high-K basalts can produce these silicic magmas. We interpret that the high-silica magmas associated Central America volcanic front are partial melts of penecontemporaneous, mantle-derived, evolved magmas that have ponded and crystallized in the mid-crust — or are melts extracted from these nearly completely crystallized magmas.

  4. Mafic and ultramafic rocks, and platinum mineralisation potential, in the Longwood Range, Southland, New Zealand

    International Nuclear Information System (INIS)

    Ashley, P.; Craw, D.; Mackenzie, D.; Rombouts, M.; Reay, A.

    2012-01-01

    Intrusive rocks in the Longwood Range represent a component of the Permian Brook Street Terrane. They include diffusely layered, cumulate-textured olivine gabbro, troctolite, and gabbro, and gradations into non-cumulate gabbro and gabbronorite. Volumetrically small ultramafic layers occur (plagioclase wehrlite), and thin veins of felsic rocks ranging from quartz diorite to trondhjemite. Primary olivine, plagioclase, clinopyroxene, and subordinate orthopyroxene and hornblende are commonly altered or metamorphosed to amphiboles, minor spinel, magnetite, chlorite, biotite and clinozoisite, and serpentine in olivine-rich rocks. Accessory primary Ti-bearing magnetite and ilmenite occur, and trace Cr-magnetite is characteristic of olivine-rich rocks. Trace pyrrhotite, chalcopyrite, pentlandite, and pyrite could reflect equilibrated late magmatic, and alteration-derived phases. Key petrochemical characteristics of the rock suite are high Mg, Al, Ca, and Sr contents, and low alkali, LILE, and sulfur contents. Platinum and Pd are locally enriched in drill-hole intercepts, but zones appear unrelated to rock type, magnetic properties, or to S, Cu, Ni, Cr, or Au values. Local platinum group element (PGE) enrichment in altered rocks implies metamorphic and/or hydrothermal redistribution. Pervasive PGE enrichment in Longwood rocks is an indicator of potential 'fertility', but evidence is currently lacking for the precipitation of primary stratiform PGE accumulations from a sulfide liquid saturated magma. (author). 41 refs., 11 figs., 2 tabs.

  5. Non-traditional stable isotope behaviors in immiscible silica-melts in a mafic magma chamber.

    Science.gov (United States)

    Zhu, Dan; Bao, Huiming; Liu, Yun

    2015-12-01

    Non-traditional stable isotopes have increasingly been applied to studies of igneous processes including planetary differentiation. Equilibrium isotope fractionation of these elements in silicates is expected to be negligible at magmatic temperatures (δ(57)Fe difference often less than 0.2 per mil). However, an increasing number of data has revealed a puzzling observation, e.g., the δ(57)Fe for silicic magmas ranges from 0‰ up to 0.6‰, with the most positive δ(57)Fe almost exclusively found in A-type granitoids. Several interpretations have been proposed by different research groups, but these have so far failed to explain some aspects of the observations. Here we propose a dynamic, diffusion-induced isotope fractionation model that assumes Si-melts are growing and ascending immiscibly in a Fe-rich bulk magma chamber. Our model offers predictions on the behavior of non-traditional stable isotope such as Fe, Mg, Si, and Li that are consistent with observations from many A-type granitoids, especially those associated with layered intrusions. Diffusion-induced isotope fractionation may be more commonly preserved in magmatic rocks than was originally predicted.

  6. Platinum, palladium, and rhodium analyses of ultramafic and mafic rocks from the Stillwater Complex, Montana

    Science.gov (United States)

    Page, Norman J; Riley, Leonard Benjamin; Haffty, Joseph

    1969-01-01

    Analyses by a combination fire- assay-solution-optical-emission spectrographic method of 137 rocks from the Stillwater Complex, Mont., indicate that platinum, palladium, and rhodium are preferentially concentrated in chromitite zones. The A chromitite zone (21 samples) has an average of 988.9 ppb (pans per billion, 10-9) Pt, 2290.2 ppb Pd, and 245.9 ppb Rh and reaches a maximum (to date) of 8,000 ppb Pt, 11,000 ppb Pd, and 1,700 ppb Rh.

  7. Geochemical characteristics of mafic and ultramafic rocks from the Naga Hills Ophiolite, India: Implications for petrogenesis

    Directory of Open Access Journals (Sweden)

    Ajoy Dey

    2018-03-01

    Full Text Available The Naga Hills Ophiolite (NHO represents one of the fragments of Tethyan oceanic crust in the Himalayan Orogenic system which is exposed in the Phek and Kiphire districts of Nagaland, India. The NHO is composed of partially serpentinized dunite, peridotite, gabbro, basalt, minor plagiogranite, diorite dyke and marine sediments. The basalts are mainly composed of fine grained plagioclase feldspar, clinopyroxene and orthopyroxene and show quenching and variolitic textures. The gabbros are characterized by medium to coarse grained plagioclase, orthopyroxene and clinopyroxene with ophitic to sub-ophitic textures. The ultramafic cumulates are represented by olivine, Cpx and Opx. Geochemically, the basalts and gabbros are sub-alkaline to alkaline and show tholeiitic features. The basalts are characterized by 44.1–45.6 wt.% of SiO2 with 28–38 of Mg#, and the gabbros by 38.7–43.7 wt.% of SiO2, and 26–79 of Mg#. The ultramafic rocks are characterized by 37.4–52.2 wt.% of SiO2, and 80–88 of Mg#. In multi-element diagrams (spidergrams both basalts and gabbros show fractionated trends with strong negative anomalies of Zr, Nb, Sr and a gentle negative anomaly of P. However, the rare earth element (REE plots of the basalts and gabbros show two distinct patterns. The first pattern, represented by light REE (LREE depletion, suggests N-MORB features and can be interpreted as a signature of Paleo-Tethyan oceanic crust. The second pattern, represented by LREE enrichment with negligible negative Eu anomaly, conforms to E-MORB, and may be related to an arc tectonic setting. In V vs. Ti/1000, Cr vs. Y and AFM diagrams, the basalts and gabbros plot within Island Arc Tholeiite (IAT and MORB fields suggesting both ridge and arc related settings. The ultramafic rocks exhibit two distinct patterns both in spidergrams and in REE plots. In the spidergram, one group displays highly enriched pattern, whereas the other group shows near flat pattern compared to primordial mantle. In the REE plot, one group displays steeper slopes [(La/YbN = 4.340–4.341], whereas the other displays moderate to flat slopes [(La/YbN = 0.97–1.67] and negative Eu-anomalies. Our study suggests that the ultramafic rocks represent two possible mantle sources (fertile and refractory.

  8. Geochemistry and petrology of mafic Proterozoic and Permian dykes on Bornholm, Denmark:

    DEFF Research Database (Denmark)

    Holm, Paul Martin; Pedersen, Lise E.; Højsteeen, Birte

    2010-01-01

    More than 250 dykes cut the mid Proterozoic basement gneisses and granites of Bornholm. Most trend between NNW and NNE, whereas a few trend NE and NW. Field, geochemical and petrological evidence suggest that the dyke intrusions occurred as four distinct events at around 1326 Ma (Kelseaa dyke...

  9. Experimental deformation of a mafic rock - interplay between fracturing, reaction and viscous deformation

    Science.gov (United States)

    Marti, Sina; Stünitz, Holger; Heilbronner, Renée; Plümper, Oliver; Drury, Martyn

    2016-04-01

    Deformation experiments were performed on natural Maryland Diabase (˜ 55% Plg, 42% Px, 3% accessories, 0.18 wt.-% H2O added) in a Griggs-type deformation apparatus in order to explore the brittle-viscous transition and the interplay between deformation and mineral reactions. Shear experiments at strain rates of ˜ 2e-5 /s are performed, at T=600, 700 and 800°C and confining pressures Pc=1.0 and 1.5 GPa. Deformation localizes in all experiments. Below 700°C, the microstructure is dominated by brittle deformation with a foliation formed by cataclastic flow and high strain accommodated along 3-5 major ultracataclasite shear bands. At 700°C, the bulk of the material still exhibits abundant microfractures, however, deformation localizes into an anastomosing network of shear bands (SB) formed from a fine-grained (<< 1 μm) mixture of newly formed Plg and Amph. These reaction products occur almost exclusively along syn-kinematic structures such as fractures and SB. Experiments at 800°C show extensive mineral reactions, with the main reaction products Amph+Plg (+Zo). Deformation is localized in broad C' and C SB formed by a fine-grained (0.1 - 0.8 μm) mixture of Plg+Amph (+Zo). The onset of mineral reactions in the 700°C experiments shows that reaction kinetics and diffusional mass transport are fast enough to keep up with the short experimental timescales. While in the 700°C experiments brittle processes kinematically contribute to deformation, fracturing is largely absent at 800°C. Diffusive mass transfer dominates. The very small grain size within SB favours a grain size sensitive deformation mechanism. Due to the presence of water (and relatively high supported stresses), dissolution-precipitation creep is interpreted to be the dominant strain accommodating mechanism. From the change of Amph coronas around Px clasts with strain, we can determine that Amph is re-dissolved at high stress sites while growing in low stress sites, showing the ability of Amph to accommodate strain via dissolution precipitation creep. The transition from dominantly brittle, to dominantly viscous deformation is determined by the onset of diffusive mass transport. In the transitional regime, reaction kinetics are strongly dependent on strain energy and viscously deforming SB form most likely from an initial brittle stage in a dominantly brittle behaving rock. Viscous deformation in our experiments takes place at comparatively low experimental T, providing a realistic phase assemblage and likely deformation mechanism for the lower crust.

  10. Volatile Contents in Mafic Magmas from two Aleutian volcanoes: Augustine and Makushin

    Science.gov (United States)

    Zimmer, M. M.; Plank, T.; Hauri, E. H.; Nye, C.; Faust Larsen, J.; Kelemen, P. B.

    2004-12-01

    There are several competing theories for the origin of tholeiitic (TH) vs. calc-alkaline (CA) fractionation trends in arc magmas. One relates to water (TH-dry magma, CA-wet magma), another to pressure (TH-low pressure crystallization, CA-high pressure), and a third to primary magma composition (TH-low Si/Fe#, CA-hi Si/Fe#) These theories have been difficult to test without quantitative measures of the water contents and pressures of crystallization of arc magmas. We are in the process of studying several Aleutian arc tephra suites (phenocrysts and melt inclusions) with the aim of obtaining volatile element concentrations (by SIMS), major and trace element concentrations and thermobarometric data (by EMP and laser-ICPMS). We report preliminary results on olivine-hosted melt inclusions from Augustine and Makushin volcanoes that support the role of water in calc-alkaline fractionation. Basaltic melt inclusions from Augustine, a low-K2O, calc-alkaline volcano, are hosted in Fo80-82 olivine. The inclusions yield high water contents, up to 5 wt%, and contain 60-90 ppm CO2, 3000-4500 ppm S, and 3000-6000 ppm Cl. Inclusions record vapor-saturation pressures near 2 kbar. Cl/K2O ratios in Augustine inclusions (ave. 1.9) are among the highest documented in an arc setting, and likely record a Cl- and H2O- rich fluid from the subducting plate. High water contents in Augustine primary melts may have contributed to the strong calc-alkaline trend observed at this volcano. Basaltic melt inclusions from Pakushin, a medium-K2O, tholeiitic cone on the flanks of Makushin volcano, are hosted in Fo80-86 olivine. These inclusions have low water contents (pressures (high sulfur (2000-4000 ppm) and Cl (>2000 ppm) in Pakushin melt inclusions, however, indicate that degassing was minimal. The low water contents and low vapor saturation pressures recorded in Pakushin melt inclusions are consistent with development of its tholeiitic trend, but we cannot distinguish whether the low water contents at Pakushin reflect a difference in the primary magma, or in crustal stresses that favor low pressure fractionation and degassing. These questions will be addressed with further work on the trace element contents of the melt inclusions and on phenocryst-melt geobarometers.

  11. Silica-poor, mafic alkaline lavas from ocean islands and continents

    Indian Academy of Sciences (India)

    Strongly silica-poor (ne-normative), mafic alkaline lavas generally represented by olivine nephelinites, nephelinites, melilitites, and olivine melilitites have erupted at various locations during Earth's history. On the basis of bulk-rock Mg#, high concentrations of Na2O, TiO2, and K2O, and trace element geochemistry, it has ...

  12. Petrologic and Oxygen-Isotopic Investigations of Eucritic and Anomalous Mafic Achondrites

    Science.gov (United States)

    Mittlefehldt, D. W.; Greenwood, R. C.; Peng, Z. X.; Ross, D. K.; Berger, E. L.; Barrett, T. J.

    2016-01-01

    The most common asteroidal igneous meteorites are eucrite-type basalts and gabbros rocks composed of ferroan pigeonite and augite, calcic plagioclase, silica, ilmenite, troilite, Ca-phosphate, chromite and Fe-metal. These rocks are thought to have formed on a single asteroid along with howardites and diogenites (HEDs). However, Northwest Africa (NWA) 011 is mineralogically identical to eucrites, but has an O-isotopic composition distinct from them and was derived from a different asteroid. Modern analyses with higher precision have shown that some eucrites have smaller O-isotopic differences that are nevertheless well-resolved from the group mean.

  13. Tracing Magmatic Degassing Timescales at Soufrière Hills Volcano using Short-Lived Uranium Series Isotopes

    Science.gov (United States)

    Turner, S.; McGee, L. E.; Handley, H. K.; Reagan, M. K.; Turner, M. B.; Berlo, K.; Barclay, J.; Sparks, R. S. J.

    2016-12-01

    Soufrière Hills Volcano, on the Caribbean island of Montserrat, is one of the most intensively studied and constantly monitored volcanic systems in the world. Since 1995, the island has seen five phases of eruption, interspersed with periods of quiescence of varying length. The last eruptive phase ended in 2010, and the current period of quiescence is the longest since 1995. Mafic recharge is thought to contribute volatiles which may lead to system overpressure and trigger a volcanic eruption. At Soufrière Hills Volcano, enclaves of mafic material are a notable feature within the andesitic dome collapse material from all five eruptive phases and have been the focus of several recent petrogenetic studies, meaning that they are extremely well-characterised. We present a 210Pb-226Ra isotope data of enclave-andesite pairs from all five recent eruption phases of Soufrière Hills to investigate the timescale on which volatile transfer occurs prior to eruptions. 210Pb-226Ra disequilibria is a powerful tool in tracing gas movement within recently erupted (<100 years) volcanic material, as one of the intermediary daughters involved in the chain (222Rn) is released in the gas phase of magmas. Subsequent deficits or excesses of 210Pb over 226Ra provide information on whether gas transfer occurred over a short time-frame or if gas fluxing from a mafic magma was maintained for some time previous to each eruption. This vital information may elucidate whether the system is recharging and preparing for a new eruptive phase or draining its current magma supply thus diminishing the possibility of further, explosive eruptions. Preliminary results suggest that gas fluxing from mafic magma was particularly effective in the first two eruptive phases, supporting the mafic-trigger hypothesis. However, we observe a possible change in this behaviour from phase 3 onwards. We complement these time-sensitive geochemical data with comparison to high resolution monitoring data with the hope

  14. Tectonic significance of dykes in the Sarnu-Dandali alkaline complex, Rajasthan, northwestern Deccan Traps

    Directory of Open Access Journals (Sweden)

    Anjali Vijayan

    2016-09-01

    Full Text Available Whether swarms of preferentially oriented dykes are controlled by regional stress fields, or passively exploit basement structural fabric, is a much debated question, with support for either scenario in individual case studies. The Sarnu-Dandali alkaline complex, near the northwestern limit of the Deccan Traps continental flood basalt province, contains mafic to felsic alkaline volcano-plutonic rocks and carbonatites. The complex is situated near the northern end of the 600 km long, NNW–SSE-trending Barmer-Cambay rift. Mafic enclave swarms in the syenites suggest synplutonic mafic dykes injected into a largely liquid felsic magma chamber. Later coherent dykes in the complex, of all compositions and sizes, dominantly strike NNW–SSE, parallel to the Barmer-Cambay rift. The rift formed during two distinct episodes of extension, NW–SE in the early Cretaceous and NE–SW in the late Cretaceous. Control of the southern Indian Dharwar structural fabric on the rift trend, as speculated previously, is untenable, whereas the regional Precambrian basement trends (Aravalli and Malani run NE–SW and NNE–SSW. We therefore suggest that the small-scale Sarnu-Dandali dykes and the much larger-scale Barmer-Cambay rift were not controlled by basement structure, but related to contemporaneous, late Cretaceous regional ENE–WSW extension, for which there is varied independent evidence.

  15. Raman spectroscopic study of the repair of surgical bone defects grafted or not with biphasic synthetic micro-granular HA + β-calcium triphosphate irradiated or not with λ850 nm LED light.

    Science.gov (United States)

    Soares, Luiz Guilherme P; Marques, Aparecida Maria C; Guarda, Milena G; Aciole, Jouber Mateus S; Andrade, Aline S; Pinheiro, Antonio Luiz B; Silveira, Landulfo

    2014-11-01

    The handling of bone losses due to different etiologic factors is difficult and many techniques are aim to improve repair, including a wide range of biomaterials and, recently, photobioengineering. This work aimed to assess, through Raman spectroscopy, the level of bone mineralization using the intensities of the Raman peaks of both inorganic (~960, ~1,070, and 1,077 cm(-1)) and organic (~1,454 and ~1,666 cm(-1)) contents of bone tissue. Forty rats were divided into four groups each subdivided into two subgroups according to the time of sacrifice (15 and 30 days). Surgical bone defects were made on the femur of each animal with a trephine drill. On animals of group clot, the defect was filled only by blood clot, on group LED, the defect filled with the clot was further irradiated. On animals of groups biomaterial and LED + biomaterial, the defect was filled by biomaterial and the last one was further irradiated (λ850 ± 10 nm, 150 mW, Φ ~ 0.5 cm(2), 20 J/cm(2)-session, 140 J/cm(2)-treatment) at 48-h intervals and repeated for 2 weeks. At both 15th and 30th days following sacrifice, samples were taken and analyzed by Raman spectroscopy. At the end of the experimental time, the intensity of hydroxyapatite (HA) (~960 cm(-1)) were higher on group LED + biomaterial and the peaks of both organic content (~1,454 and ~1,666 cm(-1)) and transitional HA (~1,070 and ~1,077 cm(-1)) were lower on the same group. It is concluded that the use of LED phototherapy associated to biomaterial was effective in improving bone healing on bone defects as a result of the increasing deposition of HA measured by Raman spectroscopy.

  16. Caracterización petrográfica y geoquímica del batolito Cerro Aspero-Alpa Corral (32°34'-32°42' LS y 64°43'-64°52' LO, provincia de Córdoba, Argentina

    Directory of Open Access Journals (Sweden)

    Porta, G.

    1992-12-01

    Full Text Available The Cerro Aspero-Alpa Corral (CA-AC batholith is a 440 km2 granite body present in the Southern edge of the Eastern Pampean Ranges, Córdoba province, central Argentina. The intrusive body of probably paleozoic age shows both post-tectonic and epizonal character. Country rocks include Upper Precambrian-Lower Paleozoic metasedimentary rocks mainly represented by mica-schists, gneisses and migmatites, locally interrupted by minor amphibolite and marble outcrops.This paper deals with representative petrographic and geochemical data that characterize a 150 km2 central stripe between 32°34'-32°42'S and 64°43'-64°52'W.Three granitic facies have been distinguished based on their distinctive modal mineralogy and texture, and upon well known chemical parameters.A K-feldspar megacryst porphydic-type is the areally prevalent facies, but dykes of micro- leucogranites and biotite-phenocryst bearing granite are also well represented. They are all monzogranites of subalkaline and peraluminous chemistry. Their mineralogy shows variable proportions of QAP constituents and micas, with minor phases represented by Fe-Ti oxides, apatite (Ap, titanite (Tt, allanite (Aln.Microgranular enclaves, abundantly distributed in the porphydic facies, provide valuable information for a better understanding of parental magma evolution.The high-Ca content of the melt makes this body quite distinctive compared to its larger northern neighbour, the Achala batholith.Pegmatite and aplite bodies, as well as fluorite bearing breccias and quartz veins, barren or mineralized, are also present within the CA-AC batholith.El batolito Cerro Aspero-Alpa Corral (CA-AC es un cuerpo granítico que aflora en el extremo sur de las Sierras Pampeanas Orientales, en la provincia de Córdoba, República Argentina, cubriendo una superficie cercana a los 440 km2.Es un cuerpo intrusivo postcinemático de probable edad paleozoica. Las rocas encajantes son metamorfitas correspondientes al Prec

  17. Isla Gorgona, enclave estratégico para los esfuerzos de conservación en el Pacífico Oriental Tropical

    Directory of Open Access Journals (Sweden)

    Alan Giraldo

    2014-02-01

    Full Text Available La Gorgona, ubicada en el sector sur del Pacífico Colombiano, es un territorio insular que se encuentra a 35km en línea recta del margen continental. Aunque históricamente tuvo diferentes usos, desde 1984 conforma una de las áreas marinas protegidas más importantes del Pacífico Colombiano. Aquí se presenta la recopilación histórica del desarrollo de la investigación científica en isla Gorgona, localidad clave para los programas de conservación marino-costeros del Pacífico Colombiano y el corredor marino de conservación del Pacífico Oriental Tropical. La integridad ecológica del PNN Gorgona es aceptable pero deben mejorarse los indicadores asociados a las poblaciones de Bradypus variegatus y Proechymis simispinosus, ya que tienen un riesgo muy elevado de desaparición. Es fundamental continuar recopilando la información técnica necesaria para ajustar los estimadores de estado de conservación.

  18. Restaurar la arquitectura, reciclar la ciudad. Vivienda social en contenedores preexistentes y enclaves estratégicos de la ciudad histórica

    Directory of Open Access Journals (Sweden)

    Mar Loren Méndez

    2009-08-01

    Full Text Available Este artículo reflexiona sobre el alcance que debe tener la vivienda social en el momento actual, que supera su limitada condición de oferta higiénica, funcional y programática. La calidad arquitectónica y su integración urbana es ya parte de esa dignidad que requiere el diseño social; la permanencia de los sectores sociales más desfavorecidos en los centros históricos y en sus arquitecturas patrimoniales debe ser así un derecho adquirido. Tras ofrecer una introducción somera del agotamiento del sueño moderno en la periferia residencial y la vuelta a la ciudad, el artículo reflexiona sobre la especulación inmobiliaria que ha rodeado a estas arquitecturas históricas en España a partir de los años ochenta del pasado siglo y que ha convertido el reciclaje de estos contenedores patrimoniales para vivivienda social en una obligación de los agentes públicos. La experiencia pionera en Andalucía de establecer una línea específica de integración de vivienda social en centros históricos es expuesta a partir de proyectos de la propia autora. Estas operaciones tienen el potencial de integrar la protección patrimonial, impedir la tematización de ciudad histórica asegurando la diversidad social y evitar en su caso la despoblación de los municipios menores.

  19. Joonised, tähendused ja unistused, ehk enklaavi eelised = From drawings to meanings and dreams: the advantage of remaining an enclave / Lilia del Rio

    Index Scriptorium Estoniae

    Rio, Lilia del

    2011-01-01

    Pirita tee alguse piirkonnast, mis oli vaatluse all 15. ja 16. juunil 2010. aastal toimunud Tallinna III linnafoorumil. Linnaruumi tegelikkusest ja Tallinna ruumilistest prioriteetidest. Rahvuspargist, rahvapargist, linnaparkidest. Plaanidest ja joonistest planeerimisprotsesside ja otstarveteni. Tallinna tulevikust

  20. Enclave económico y sociedad local: la conformación de la identidad comarcal en la cuenca minera de Riotinto

    Directory of Open Access Journals (Sweden)

    Javier Escalera Reyes

    1992-02-01

    Full Text Available La comarca que conocemos como la Cuenca Minera de Ríotinto comprende una extensión de 453,9 km , y de ella forman parte siete municipios: Zalamea (3.948 ha., El Campillo (2.850 ha., Ríotinto (6.013 ha., Nerva (7.208 ha., Campofrío (896 ha., Berrocal (428 ha. y La Granada (234 ha.. Se podría decir que Zalamea es el núcleo matriz originario de la comarca, pues de su término municipal nacieron , segregándose, Ríotinto (1841, Nerva (1885 y El Campillo (1931. El factor explicativo principal para entender la comarca -su configura­ción espacial, las pautas de poblamiento , su economía, sus formas de articulación social, la mentalidad y peculiaridad es culturales-, es la actividad minera. Se podría decir que la minería ha "creado" la comarca. Las minas fueron vendidas a una compañía británica en 1873, en 1954 pasaron a un consorcio español, desde mediados de los ochenta pertenecen al Holding Ercross (controlado hasta muy recientemente por el grupo KIO y actualmente (enero de 1993 han sido compra das por la corporación norteamericana Free Port Macmoran. Las empresas mineras han sustituido desde fines del siglo XIX, y hasta hace pocas fechas, al estado en las funciones propias de éste en la comarca, teniendo el control absoluto sobre todos los ámbitos de la vida comarcal: vivienda, infraestructuras, comunicaciones, servicios, e incluso sobre la propia sociedad en cuanto a los principales cauces y modos de expresión de la sociabilidad y de la acción sociopolítica, así como en cuanto a los liderazgos y grupos de prestigio y poder.

  1. CABO FRIO - AN ENCLAVE IN SEMI ARID COASTAL MOIST OF RIO DE JANEIRO STATE: INFLUENCES OF CLIMATE AND PRESENT PAST VEGETATION

    Directory of Open Access Journals (Sweden)

    Heloisa Helena Gomes Coe

    2013-04-01

    Full Text Available Localizada na costa NE do Estado do Rio de Janeiro, Brasil, a região de Cabo Frio tem sido considerada um “enclave” fitogeográfico, com um clima mais seco que o restante do litoral fluminense, reduto de vegetação semelhante à caatinga, dominada por florestas xeromórficas, Cactaceae e Bromeliaceae. Objetivando contribuir para esta discussão de modo singular, este trabalho faz análises multivariadas de similaridade de variáveis do clima atual, comparando Cabo Frio com seu entorno mais úmido e com a caatinga do Nordeste brasileiro, e estuda possíveis variações da paleovegetação na região, utilizando como indicadores os fitólitos. Conclui-se que o clima de Cabo Frio se assemelha mais à caatinga que ao seu entorno, e que a vegetação, desde 13.000 anos cal AP, foi sempre de tipo pouco arbórea.

  2. Captación de agua de niebla en determinados enclaves del sudeste de la Península Ibérica

    OpenAIRE

    Corell, David; Estrela, María Jesús; Valiente, José A.; Barceló, Susana; Capel Molina, José Jaime

    2014-01-01

    Ponencia presentada en: IX Congreso de la Asociación Española de Climatología celebrado en Almería entre el 28 y el 30 de octubre de 2014. [ES]El sudeste de la Península Ibérica y, en concreto, las provincias de Alicante, Murcia y Almería, es un área especialmente sensible a la problemática de la escasez de agua, debido a su clima de escasas precipitaciones y de sus habituales periodos largos sin lluvias. Es por ello, que la búsqueda de fuentes de agua alternativas puede ayudar a ...

  3. Evaluation of the effects of alteration and leaching on Sm Nd and Lu Hf systematics in submarine mafic rocks

    Science.gov (United States)

    Thompson, Patricia M. E.; Kempton, Pamela D.; Kerr, Andrew C.

    2008-08-01

    Nd and Hf isotope systematics of oceanic basaltic rocks are often assumed to be largely immune to the effects of hydrothermal alteration. We have tested this assumption by comparing Nd and Hf isotope data for acid-leached Cretaceous oceanic basalts from Gorgona and DSDP Leg 15 with unleached data on the same rocks. Hf isotope values and Lu/Hf ratios are relatively unaffected by leaching, but 143Nd/ 144Nd values of leached samples are significantly higher than those of unleached fractions of the same sample in most cases. Furthermore, the Sm/Nd ratios of the majority of leached samples are 10-40% greater than those of unleached samples. X-ray diffraction studies indicate that selective removal of secondary minerals, such as smectite, during the acid leaching process is responsible for the fractionation of Sm/Nd ratios. These results have implications for interpretation of the Hf-Nd isotope systematics of ancient submarine rocks (older than ~ 50 Ma), as (1) the age-corrected 143Nd/ 144Nd ratio may not be representative of the primary magmatic signature and (2) the uncertainty of the age-corrected ɛNd value may exceed the assumed analytical precision.

  4. A model of sulphur solubility for hydrous mafic melts: application to the determination of magmatic fluid compositions of Italian volcanoes

    Directory of Open Access Journals (Sweden)

    M. Pichavant

    2005-06-01

    Full Text Available We present an empirical model of sulphur solubility that allows us to calculate f S2 if P, T, fO2 and the melt composition, including H2O and S, are known. The model is calibrated against three main experimental data bases consisting in both dry and hydrous silicate melts. Its prime goal is to calculate the f S2 of hydrous basalts that currently lack experimental constraints of their sulphur solubility behaviour. Application of the model to Stromboli, Vesuvius, Vulcano and Etna eruptive products shows that the primitive magmas found at these volcanoes record f S2 in the range 0.1-1 bar. In contrast, at all volcanoes the magmatic evolution is marked by dramatic variations in f S2 that spreads over up to 9 orders of magnitude. The f S2 can either increase during differentiation or decrease during decompression to shallow reservoirs, and seems to be related to closed versus open conduit conditions, respectively. The calculated f S2 shows that the Italian magmas are undersaturated in a FeS melt, except during closed conduit conditions, in which case differentiation may eventually reach conditions of sulphide melt saturation. The knowledge of f S2, fO2 and fH2O allows us to calculate the fluid phase composition coexisting with magmas at depth in the C-O-H-S system. Calculated fluids show a wide range in composition, with CO2 mole fractions of up to 0.97. Except at shallow levels, the fluid phase is generally dominated by CO2 and H2O species, the mole fractions of SO2 and H2S rarely exceeding 0.05 each. The comparison between calculated fluid compositions and volcanic gases shows that such an approach should provide constraints on both the depth and mode of degassing, as well as on the amount of free fluid in magma reservoirs. Under the assumption of a single step separation of the gas phase in a closed-system condition, the application to Stromboli and Etna suggests that the main reservoirs feeding the eruptions and persistent volcanic plumes at these volcanoes might contain as much as 5 wt% of a free fluid phase. Consideration of the magma budget needed to balance the amounts of volatiles emitted in the light of these results shows that the amount of nonerupted magma could be overestimated by as much as one order of magnitude.

  5. Investigating Natural Analogues for Co{sub 2} Sequestration in Ultra Mafic Rocks: A Reactive Transport Modelling Approach

    Energy Technology Data Exchange (ETDEWEB)

    Gherardi, F. [Istituto di Geoscienze e Georisorse, Consiglio Nazionale delle Ricerche, Pisa (Italy)

    2013-07-15

    Serpentinites of Ligurian ophiolites are studied as natural analogues for CO{sub 2} mineral sequestration in Italy. Mineralogical and geochemical observations indicate that silicification and carbonation are typical alteration processes induced by the interaction of CO{sub 2} charged fluids with pristine ultramafic rocks. Multicomponent reactive transport models have been applied to reproduce natural patterns and investigate carbon sequestration efficiency under high P{sub CO2} conditions. Temporal changes in porosity and permeability are predicted to affect the spatial and temporal occurrence of secondary minerals. The feedback between mineralogical transformations and transport properties of the geological media emerges as a key factor controlling the mineral carbonation potential of the investigated ultramafic rocks. (author)

  6. The Formation of Carbonate Minerals and the Mobility of Heavy Metals during Water-CO2-Mafic Rock Interactions

    DEFF Research Database (Denmark)

    Olsson, Jonas

    to the carbonate precipitation in CarbFix project. In the third study, water and solid samples from two alkaline springs in Oman were examined. The elements detected in the spring waters in order of abundance were Na, Cl, Ca, Mg, SO4, K, Br, Si, F, B, Sr, Al, Fe, Mo, Zn, Ni, Cu, Mn, V, Ba, Cr, Co, Ti, Hg and Pb...

  7. Seismic constraints on a large mafic intrusion with implications for the subsidence mechanism of the Danish Basin

    DEFF Research Database (Denmark)

    Sandrin, Alessandro; Thybo, Hans

    2008-01-01

    Gal) positive gravity anomaly known as Silkeborg Gravity High. The intrusion has a minimum volume of 40,000 km3, which implies that the magma influx and the consequent cooling of the lithosphere from high temperature could have had profound effects on the subsidence of the Danish Basin, in particular because...

  8. Experimental investigation of the brittle-viscous transition in mafic rocks - Interplay between fracturing, reaction, and viscous deformation

    Science.gov (United States)

    Marti, Sina; Stünitz, Holger; Heilbronner, Renée; Plümper, Oliver; Drury, Martyn

    2017-12-01

    Rock deformation experiments are performed on fault gouge fabricated from 'Maryland Diabase' rock powder to investigate the transition from dominant brittle to dominant viscous behaviour. At the imposed strain rates of γ˙ = 3 ·10-5 - 3 ·10-6 s-1, the transition is observed in the temperature range of (600 °C < T < 800 °C) at confining pressures of (0.5 GPa ≤ Pc ≤ 1.5 GPa). The transition thereby takes place by a switch from brittle fracturing and cataclastic flow to viscous dissolution-precipitation creep and grain boundary sliding. Mineral reactions and resulting grain size refinement by nucleation are observed to be critical processes for the switch to viscous deformation, i.e., grain size sensitive creep. In the transitional regime, the mechanical response of the sample is a mixed-mode between brittle and viscous rheology and microstructures associated with both brittle and viscous deformation are observed. As grain size reduction by reaction and nucleation is a time dependent process, the brittle-viscous transition is not only a function of T but to a large extent also of microstructural evolution.

  9. Clay mineralogy and geochemistry of the soils derived from metamorphic and mafic igneous parent rocks in Lahijan area

    International Nuclear Information System (INIS)

    Ramezanpour, H.; Hesami, R.; Zanjanchi, M. A.

    2007-01-01

    The mineralogical and geochemical composition of the soils of three representative pedons formed on basaltic andesite, andesitic basalt and phyllite were investigated. Results by x-ray diffraction showed that progressive weathering of rocks have been marked by gradual accumulation of Al, Fe, Ti, Mg, H 3 O + and depletion of Na, K, Ca and Si in the soil; although, predominant clay, loss and gain trend of elements was different on the various rocks. Based on x-ray diffraction analysis, minerals in basaltic andesite and andesitic basalt were similar but, the intensity of mica to smectite or vermiculite transformation for latter was relatively higher than the former. This process revealed the degradation mineral because of two reasons: (i) - smectite and vermiculite increased whereas mica decreased in surface horizons. (i i)-Irregular mixed layer of mica-smectite or vermiculite was present in deeper part (170 cm) of the soils from andesitic basalt but shallower depth (75 em) of the soils from basaltic andesite. Clay minerals in phyllite were mica and chlorite that stratified with vermiculite. However, the absence of smectite in phyllite might be attributed to more acidic condition or position of the Fe ion in the mineral lattice of chlorite (higher Fe in the interlayer hydroxide sheet)

  10. Metamorphic chlorite and "vermiculitic" phases in mafic dikes from the Maláguide Complex (Betic Cordillera, Spain)

    Czech Academy of Sciences Publication Activity Database

    Ruiz Cruz, M. D.; Novák, Jiří Karel

    2003-01-01

    Roč. 15, č. 1 (2003), s. 1-14 ISSN 0935-1221 Grant - others:Ministerio de Educación y Cultura(ES) BTE-2000-1150; Research Group(ES) RNM-199 Institutional research plan: CEZ:AV0Z3013912 Keywords : low-grade metamorphism * vermiculite * Betic Cordillera Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.185, year: 2003

  11. Rb-Sr and Nd-Sr isotope geochemistry and petrogenesis of the Misho Mountains mafic dikes (NW Iran)

    OpenAIRE

    Maryam Ahankoub; Yoshihiro Asahar

    2017-01-01

    Introduction There are some theories about the Paleotethys event during the Paleozoic that have been proposed by geologists (Metcalfe, 2006). Some scientist offered some pieces of evidence about the northern margin of Gondwana (Zhu et al., 2010). The Paleotethys Ocean and Hercynian orogenic report first in Iran, have been Offered from the Morrow and Misho Mountain (Eftekharnejad, 1981). Misho Mountains is located between the north and south Misho faults and cause the formation of a positi...

  12. Precursory activity of the 161 ka Kos Plateau Tuff eruption, Aegean Sea (Greece)

    Science.gov (United States)

    Piper, David J. W.; Pe-Piper, Georgia; Lefort, Darren

    2010-08-01

    The Kos Plateau Tuff (KPT) eruption of 161 ka was the largest explosive Quaternary eruption in the eastern Mediterranean. We have discovered an uplifted beach deposit of abraded pumice cobbles, directly overlain by the KPT. The pumice cobbles resemble pumice from the KPT in petrography and composition and differ from Plio-Pleistocene rhyolites on the nearby Kefalos Peninsula. The pumice contains enclaves of basaltic andesite showing chilled lobate margins, suggesting co-existence of two magmas. The deposit provides evidence that the precursory phase of the KPT eruption produced pumice rafts, and defines the paleoshoreline for the KPT, which elsewhere was deposited on land. The beach deposit has been uplifted about 120 m since the KPT eruption, whereas the present marine area south of Kos has subsided several hundred metres, as a result of regional neotectonics. The basaltic andesite is more primitive than other mafic rocks known from the Kos-Nisyros volcanic centre and contains phenocrysts of Fo89 olivine, bytownite, enstatite and diopside. Groundmass amphibole suggests availability of water in the final stages of magma evolution. Geochemical and mineralogical variation in the mafic products of the KPT eruption indicate that fractionation of basaltic magma in a base-of-crust magma chamber was followed by mixing with rhyolitic magma during eruption. Low eruption rates during the precursory activity may have minimised the extent of mixing and preserved the end-member magma types.

  13. The Fontaine Pluton : an early Ross Orogeny calc-alkaline gabbro from southern Victoria Land, Antarctica

    International Nuclear Information System (INIS)

    Cottle, J.M.; Cooper, A.F.

    2006-01-01

    The Fontaine Pluton is a previously undescribed mafic intrusion outcropping at Fontaine Bluff on the south side of the Carlyon Glacier in southern Victoria Land, Antarctica. It is the southern-most member of a laterally extensive mafic suite emplaced at mid-crustal depths during the initial stages of the Ross Orogeny. The pluton comprises recrystallised hornblende-biotite gabbro, which in places shows well-defined centimetre to metre scale primary igneous layering. Recrystallised ultramafic enclaves composed of amphibole-chlorite-talc are inferred to be remnants of a chemically and mineralogically distinct cumulate fraction. The intrusion has a 87 Sr/ 86 Sr (i) ratio of 0.70679 and a 143 Nd/ 144 Nd (i) ratio of 0.51187 (εNd (i) = -1.2). This, coupled with other geochemical data, implies that the Fontaine Pluton was formed by c. 15% partial melting of a depleted mantle source that was subsequently contaminated by continental crust. Preliminary U-Pb geochronology on zircon suggests an emplacement age for the pluton of 546 ± 10 Ma. These new data indicate that Ross Orogeny magmatism in this area of southern Victoria Land was initiated in the late Neoproterozoic along a subducting plate margin. (author). 55 refs., 10 figs., 3 tabs

  14. Semi-adakitic magmatism of the Satkatbong diorite, South Korea: Geochemical implications for post-adakitic magmatism in southeastern Eurasia

    Science.gov (United States)

    Lim, Hoseong; Woo, Hyeon Dong; Myeong, Bora; Park, Jongkyu; Jang, Yun-Deuk

    2018-04-01

    The Satkatbong diorite (190 Ma) and the older Yeongdeok granite (250 Ma) in the Yeongnam massif, which is part of the southeastern margin of the Eurasian plate, are affected by a subduction system that is associated with the Izanagi and Farallon plates. The Satkatbong diorite is characterized by its abundant mafic magmatic enclaves (MMEs), mantle affinity, and intermediate adakitic Sr/Y vs. Y signature, whereas the Yeongdeok granite is distinctly adakitic and felsic and contains few MMEs. These differences in adakitic features might be due to differences in the lithospheric mantle material and/or different mafic MME sources. The results of rare earth element (REE) analyses and newly proposed Sr/La modeling in this study indicate that these two plutons were both generated by slab-mantle mixing and continental assimilation, whereas the Satkatbong diorite was additionally affected by the injection of a mafic source of MMEs, which "diluted" its adakitic chemistry. The young and hot subducting ridge passing toward the northeast due to the oblique subduction of the Izanagi and Farallon plates during the Early Mesozoic could have given rise to slab melting and asthenospheric influence through slab melting regions and a slab window, respectively. This implies that the adakitic Yeongdeok granite produced by slab melting and then the semi-adakitic Satkatbong diorite produced by asthenospheric influence, including other similar adakitic to semi-adakitic magmatism, might have occurred along the areas affected by ridge subduction. We suggest that this sequential magmatism would be applicable for many continental arcs which experienced ridge subduction being one of the mechanisms of adakite to semi-adakite magmatism.

  15. DE LA CUESTIÓN AGROPECUARIA, LAS ECONOMÍAS DE ENCLAVE Y LOS DESEQUILIBRIOS ECOLÓGICOS EN EL VALLE DE MALVAZÁ: UN ANÁLISIS ECONÓMICO DE IMPACTO AMBIENTAL THE ECONOMIES OF ENCLAVE AND THE ECOLOGICAL IMBALANCES IN MALVAZÁ's VALLEY: AN ECONOMIC ANALYSIS OF ENVIRONMENTAL IMPACTE

    Directory of Open Access Journals (Sweden)

    JUAN JOSÉ CAICEDO COLLAZOS

    2008-12-01

    Full Text Available A pesar de importantes avances en materia ambiental en Colombia, las dinámicas socioeconómicas que caracterizan los espacios rurales y urbanos influyen en la generación de desequilibrios ambientales, imprimiendo así, cierta singularidad al desarrollo sostenible de la nación. Los páramos como otros activos ambientales son objeto de formas específicas de relacionamiento, soportando graves procesos de degradación y transformación, originados principalmente en el cambio de uso del suelo, y el desarrollo de actividades sectoriales y agropecuarias inadecuadas. Este trabajo, hace uso de instrumentos de economía política del medio ambiente, para examinar la interacción compleja entre la sociedad y la naturaleza en el espacio geográfico del corregimiento de Gabriel López, asumiendo el análisis de la coyuntura y la estructura socio-productiva de la zona, los principales impactos ambientales sobre el Páramo de Las Delicias; y realizando una estimación monetaria de las alteraciones en el bienestar de los moradores del lugar frente a la problemática. Para concluir señalando elementos de juicio para la construcción de un mecanismo de incentivos que soporte el entramado socio-ambiental en la zona.In spite of important advances in environmental matter in Colombia, the socioeconomic dynamics that characterize the rural and urban spaces influence in the generation of environmental imbalances, stamping, certain singularity like that on the sustainable development of the nation. The high plateaus like other environmental assets are an object of specific forms of relationship, supporting serious processes of degradation and transformation, originated principally in the change of use of the soil, and to the development of sectorial and agricultural inadequate activities. This work makes use instruments of political economy of the environment, to examine the complex interaction between the society and the nature in the geographical space of Gabriel López, assuming the analysis of the conjuncture and the structure associate productive of the zone, the principal environmental impacts on The Delicias high plateau; And realizing a monetary estimation of the alterations in the well-being of the local inhabitants opposite to the problematic. To end up by indicating facts for the construction of a mechanism of incentives that environmental associate should support the studding in the zone.

  16. Plagioclase-mantled K-feldspar in the Carboniferous porphyritic microgranite of Altenberg-Frauenstein, Eastern Erzgebirge/Krusné Hory

    Directory of Open Access Journals (Sweden)

    Axel Müller

    2002-01-01

    Full Text Available The Upper Carboniferous porphyritic microgranite of Altenberg-Frauenstein, formerly known as Granitporphyr (Dalmer 1896 and here abbreviated as GP, forms a 36 km long and up to 18 km wide complex of ring dykes related to the Teplice-Altenberg caldera in the German–Czech border region of the Eastern Erzgebirge/Krusné Hory. The microgranites are characterized by the occurrence of plagioclase-mantled K-feldspar phenocrysts. The microgranite varieties representtwo main stages of intrusion evolved from acid (GP I to intermediaterocks (GP II within the intrusion. The most acid rock (GP Icum occurs as enclaves in GP I and GP II and is interpreted as a cumulate of K-feldspar and quartz phenocrysts. The porphyritic microgranites show field, textural and geochemical evidence suggesting that some of them have formed as a result of interaction between felsic and mafic magmas. Mixing features are abundant in the porphyriticquartz-feldspar-hornblende microgranite (GP II interpreted as a hybrid rock. They are less discrete in the early phase (GP I and not obvious in the acid enclaves (GP Icum. This trend seems to reflect a continuous deflation of the magma chamber from the top to the bottom. According to the definition of rapakivi granites after Haapala and Rämö (1992, the porphyritic microgranite of Altenberg-Frauenstein may be considered as rapakivi granite although ovoid alkali feldspar megacrysts typical of classical rapakivi granites are not recorded.However, due to its Carboniferous age and being the only known granitewith rapakivi texture in the German–Czech part of the Variscan belt, the microgranite of Altenberg-Frauenstein is exceptional.

  17. Energy-constrained open-system magmatic processes IV: Geochemical, thermal and mass consequences of energy-constrained recharge, assimilation and fractional crystallization (EC-RAFC)

    International Nuclear Information System (INIS)

    Wendy A. Bohrson Department of Geological Sciences, Central Washington University, Ellensburg, Washington, 98926, USA; Frank J. Spera Institute for Crustal Studies and Department of Geological Sciences, University of California, Santa Barbara, California, 93106, USA

    2003-01-01

    A wealth of geochemical and petrological data provide evidence that the processes of fractional crystallization, assimilation, and magma recharge (replenishment) dominate the chemical signatures of many terrestrial igneous rocks. Previous work [Spera and Bohrson, 2001 ; Bohrson and Spera, 2001] has established the importance of integrating energy, species and mass conservation into simulations of complex magma chamber processes. An extended version of the energy-constrained formulation, Energy-Constrained Recharge, Assimilation, Fractional Crystallization (EC-RAFC), tracks mass and compositional variations of melt, cumulates, and enclaves in a magma body undergoing simultaneous recharge, assimilation, and fractional crystallization [Spera and Bohrson, 2002]. Because many EC-RAFC results are distinct from those predicted by extant RAFC formulations, the primary goal of this paper is to present a range of geochemical and mass relationships for selected cases that highlight issues relevant to modern petrology. Among the plethora of petrologic problems that have important, well-documented analogues in nature are the geochemical distinctions that arise when a magma body undergoes continuous versus episodic recharge, the connection between erupted magmas and associated cumulate bodies, the behavior of recharge-fractionation dominated systems (RFC), thermodynamic conditions that promote the formation of enclaves versus cumulates, and the conditions under which magma bodies may be described as chemically homogeneous. Investigation of the effects of continuous versus episodic recharge for mafic magma undergoing RAFC in the lower crust indicates that the resulting geochemical trends for melt and solids are sensitive to the intensity and composition of recharge, suggesting that EC-RAFC may be used as a tool to distinguish the nature of the recharge events. Compared to the record preserved in melts, the geochemical and mass characteristics of solids associated with particular

  18. Petrologia do Granito Chasqueiro, região de Arroio Grande, sudeste do Escudo Sul-Rio-Grandense

    Directory of Open Access Journals (Sweden)

    Daniel Triboli Vieira

    Full Text Available RESUMO: O Granito Chasqueiro aflora como campos de matacões e lajeados, que em planta constituem um corpo alongado segundo N50oE com área de aproximadamente 400 km2, localizado no sul da porção oriental do Escudo Sul-Rio-Grandense. Compreende de monzo a sienogranito, leucocrático de cor cinza-clara e textura porfirítica com megacristais de K-feldspatos em matriz equigranular, hipidiomórfica grossa, composta por quartzo, K-feldspato, plagioclásio, biotita, hornblenda, minerais opacos e acessórios. Os megacristais atingem proporções modais entre 30,0 e 60,0%, e variam entre 4 e 8 cm, que com os minerais máficos da matriz evidenciam uma foliação de fluxo magmático subvertical bem desenvolvida que transaciona lateralmente para uma foliação tectônica nos bordos do granito próximo às zonas de cisalhamento onde ocorrem extensas faixas marcadas por intensa deformação dúctil e geração de protomilonitos. O granito apresenta enclaves máficos microgranulares de composição diorítica, apresentando diferentes formas e tamanhos. Geoquimicamente, é caracterizado por um magmatismo subalcalino do tipo cálcio-alcalino de alto potássio, metaluminoso a levemente peraluminoso, com assinatura característica de granitos gerados em ambiente pós-colisional. Processos de fusão crustal, mistura de magmas e cristalização fracionada são sugeridos para a sua evolução. Análises geocronológicas obtidas pelo método U-Pb (LA-ICP-MS e geoquímica isotópica de Lu-Hf (LA-ICP-MS em zircões indicaram, respectivamente, idade de cristalização 574 ± 3 Ma e valores negativos para εHf, sugerindo assim uma relação do Granito Chasqueiro com o evento deformacional D2 e fontes magmáticas dominantemente crustais com participação de componente mantélico subordinado.

  19. Geochemistry and petrogenesis of the Kolah-Ghazi granitoid assemblage, south of Esfahan

    Directory of Open Access Journals (Sweden)

    Jamshid Ahmadian

    2018-04-01

    Full Text Available Introduction The Kolah-Ghazi granitoid assemblage is located in the south of Esfahan and in the Sanandaj-Sirjan magmatic-metamorphic zone. The Sanandaj-Sirjan zone is extended for 1500 km from Sirjan in the southeast to Sanandaj in the northwest of Iran and is situated in the west of Central Iranian terrane. The Sanandaj-Sirjan zone represents the metamorphic belt of the Zagros orogeny which is part of the Alpine- Himalayan orogenic belt. The Kolah-Ghazi granitoid assemblage consists of granodiorite, granites, quartz-rich granitoid and minor tonalite. The aim of this paper is to represent the mineralogy, geochemistry, petrogenesis and tectonic setting of this plutonic assemblage. Materials and methods More than 60 samples representing all of the rock units in the study area were chosen for microscopic studies. Then, 22 samples were selected for geochemical studies. The major elements were determined with XRF in the Naruto University, Japan. The trace and rare earth elements were analyzed by ICP-MS in the Acmelab, Canada. The geochemical results are presented in Table 1. Results and Discussion The Kolah-Ghazi granitoid assemblage intruded into the Jurassic sedimentary units and overlaid by lower Cretaceous sandstone and conglomerate which suggest Upper Jurassic as the possible age of the Kolah-Ghazi intrusion. Based on the modal studies, this granitoid assemblage is comprised of granite, granodiorite, quartz-rock granitoid and tonalite with different igneous textures including symplectic, myrmekitic, rapakivi, poikilitic and porphyroid. There are some xenoliths, microgranular enclaves and sur micaceous enclaves in the Kolah-Ghazi granitoid assemblage. Xenoliths are mostly derived from Jurassic shale and sandstones which have been trapped in the magma. The sur micaceousenclaves have tonalite composition. The sur micaceous enclaves are biotite-rich rock fragments which display metamorphic texture. The sur micaceous enclaves are classified as

  20. Amphibole Thermometry and a Comparison of Results from Plutonic and Volcanic Systems

    Science.gov (United States)

    Sherman, T. M.; Putirka, K. D.; De Los Reyes, A. M. A.; Ratschbacher, B. C.

    2015-12-01

    Recent work (Ridolfi and Renzulli 2014) shows that amphiboles can be used to infer magmatic temperatures, even without knowledge of co-existing liquids. Here, we apply this approach, using new calibrations, to investigate felsic-mafic magma interactions, in a volcanic (Lassen Volcanic Center, a Cascade volcano) and plutonic (the Jurassic Guadalupe Igneous Complex) system. Preliminary data suggest that volcanic processes, as might be expected, preserve higher temperatures than plutonic materials (on average, volcanic amphiboles recorded 907±57.3°C while plutonic amphiboles recorded 764±59.7°C). We also find that the average T of a given mineral grain decreases with increased mineral size such that those crystallized below 800°C sometimes reach sizes beyond ~1mm, while those near 900°C appear truncated to ~0.3mm. It is not clear if T is the only control on amphibole crystal growth; however, our results would imply that larger grains not only require more time to grow but require continued undercooling. Significant cooling or heating is also recorded in many volcanically- and plutonically-grown grains, which may reflect transitioning between magmas of different T and composition. Core-to-rim cooling trends (with a common T of drop of 80oC) likely represent mafic-to-felsic magma transitions, whereas core-to-rim heating of similar magnitudes indicate a felsic-mafic transition. Some grains, though, exhibit a constant T (in the range 700-900°C) from core to rim, which perhaps indicates some shielding from magma mixing processes. Amphiboles might thus provide a reliable record of the intensity of magma mingling and mixing experienced by any particular enclave. Interestingly, volcanically-derived amphiboles appear to mostly record cooling towards the rims, while their plutonic counterparts tend to experience heating. It would thus appear that at Lassen, amphiboles are unaffected by later mafic magma recharge, but at the GIC, the plutonic amphiboles are more likely to

  1. Poly-phase Deformation Recorded in the Core of the Coast Plutonic Complex, Western British Columbia

    Science.gov (United States)

    Hamblock, J. M.; Andronicos, C. L.; Hurtado, J. M.

    2006-05-01

    The Coast Plutonic Complex of western British Columbia constitutes the largest batholith within the North American Cordillera. The field area for this study is Mt. Gamsby, an unexplored region above the Kitlope River, east of the Coast Shear Zone and at the southern end of the Central Gneiss Complex. The dominant lithologies on Mt. Gamsby include amphibolite and metasedimentary gneiss, gabbro-diorite, and orthogneiss. The amphibolite gneiss contains alternating amphibolite and felsic layers, with chlorite and epidote pervasive in some regions and garnet rare. This unit is commonly migmatized and contains various folds, boudins, and shear zones. The metasedimentary gneiss contains quartz, k-spar, graphite, chlorite, and perhaps cordierite, but appears to lack muscovite and aluminosilicates. The gabbro-diorite is salt and pepper in color and contains ca. 50% pyroxene and plagioclase. The orthogneiss is light in color and plagioclase-rich, with a texture varying from coarse-grained and undeformed to mylonitic. In some regions, this unit contains abundant mafic enclaves. At least four deformational events (D1-4) are observed. The second generation of folding, F2, is dominant in the area and resulted in the production of a large synform during sinistral shearing. The S1 foliation is observed only in the amphibolite gneiss and is orthogonal to S2, creating mushroom- type fold interference patterns. S2 foliations strike NW-SE and dip steeply to the SW, suggesting SW-NE directed shortening. L2 lineations developed on S2 plunge shallowly to the NW and SE, implying strike-slip motion. Although both dextral and sinistral motions are indicated by shear band data, sinistral motion is dominant. The average right and left lateral shear band orientation is nearly identical to S2, suggesting that right and left lateral shearing were synchronous. Foliations within the orthogneiss are parallel to the axes of S2 folds and boudins in the amphibolite gneiss, suggesting that emplacement

  2. Coeval interaction between magmas of contrasting composition (Late Carboniferous-Early Permian Santa Eulália-Monforte massif, Ossa-Morena Zone): field relations and geochronological constraints

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, M.F.; Gama, C.; Rodríguez, C.

    2017-07-01

    The Santa Eulália-Monforte massif is a post-kinematic Late Carboniferous-Early Permian calc-alkaline composite massif (LC-EP) located in the Ossa-Morena Zone (OMZ, Portugal). This paper examines the field relationships between pinkish granites and mafic-intermediate rocks from the external ring of this massif and presents new U-Pb zircon age determinations. The estimated 206Pb/238U ages, 297±4Ma for the pinkish granite and 303±3Ma for a gabbro-diorite point to a short time interval between the crystallization of both magmas. At outcrop scale, contacts of the mafic-intermediate rocks with the host pinkish granite are sharp and corroborate this age relationship, but do not justify why the host-enclave contacts often has curved and irregular shapes, indicating liquid-liquid interaction. A full analysis of the distribution of U-Pb zircon ages and respective Th/U ratios suggests that the compositionally distinct magmas were roughly contemporaneous. The obtained ages also fit the LC-EP Iberian calc-alkaline suite that was formed contemporaneously to the development of the Iberian-Armorican Arc and when the Paleotethyan oceanic Plate subducted under the Eurasian active margin. Taking this geodynamic setting as a reference, the LC-EP Iberian calc-alkaline magmatism can be interpreted as most probably related to the Cimmerian cycle instead of the traditionally accepted model that ascribe a closer connection of this magmatism with the Variscan cycle. The Santa Eulália-Monforte massif is a post-kinematic Late Carboniferous-Early Permian calc-alkaline composite massif (LC-EP) located in the Ossa-Morena Zone (OMZ, Portugal). This paper examines the field relationships between pinkish granites and mafic-intermediate rocks from the external ring of this massif and presents new U-Pb zircon age determinations. The estimated 206Pb/238U ages, 297±4Ma for the pinkish granite and 303±3Ma for a gabbro-diorite point to a short time interval between the crystallization of both

  3. Coeval interaction between magmas of contrasting composition (Late Carboniferous-Early Permian Santa Eulália-Monforte massif, Ossa-Morena Zone): field relations and geochronological constraints

    International Nuclear Information System (INIS)

    Pereira, M.F.; Gama, C.; Rodríguez, C.

    2017-01-01

    The Santa Eulália-Monforte massif is a post-kinematic Late Carboniferous-Early Permian calc-alkaline composite massif (LC-EP) located in the Ossa-Morena Zone (OMZ, Portugal). This paper examines the field relationships between pinkish granites and mafic-intermediate rocks from the external ring of this massif and presents new U-Pb zircon age determinations. The estimated 206Pb/238U ages, 297±4Ma for the pinkish granite and 303±3Ma for a gabbro-diorite point to a short time interval between the crystallization of both magmas. At outcrop scale, contacts of the mafic-intermediate rocks with the host pinkish granite are sharp and corroborate this age relationship, but do not justify why the host-enclave contacts often has curved and irregular shapes, indicating liquid-liquid interaction. A full analysis of the distribution of U-Pb zircon ages and respective Th/U ratios suggests that the compositionally distinct magmas were roughly contemporaneous. The obtained ages also fit the LC-EP Iberian calc-alkaline suite that was formed contemporaneously to the development of the Iberian-Armorican Arc and when the Paleotethyan oceanic Plate subducted under the Eurasian active margin. Taking this geodynamic setting as a reference, the LC-EP Iberian calc-alkaline magmatism can be interpreted as most probably related to the Cimmerian cycle instead of the traditionally accepted model that ascribe a closer connection of this magmatism with the Variscan cycle. The Santa Eulália-Monforte massif is a post-kinematic Late Carboniferous-Early Permian calc-alkaline composite massif (LC-EP) located in the Ossa-Morena Zone (OMZ, Portugal). This paper examines the field relationships between pinkish granites and mafic-intermediate rocks from the external ring of this massif and presents new U-Pb zircon age determinations. The estimated 206Pb/238U ages, 297±4Ma for the pinkish granite and 303±3Ma for a gabbro-diorite point to a short time interval between the crystallization of both

  4. Granitoids of the Dry Valleys area, southern Victoria Land, Antarctica : plutons, field relationships, and isotopic dating

    International Nuclear Information System (INIS)

    Allibone, A.H.; Cox, S.C.; Johnstone, R.D.

    1993-01-01

    Detailed mapping throughout much of the Dry Valleys area indicates the region is underlain by 15 major granitoid plutons and numerous smaller plugs and dikes. Intrusive relationships of these plutons and dikes indicate repeated intrusion of superficially similar granitoids at different times. Sufficient internal lithologic variation occurs within individual plutons, to allow correlation with several of the previously defined granitoid units based on lithologic character. Consequently, previous subdivision schemes based on lithology are no longer tenable and are here replaced with a subdivision scheme based on the identification of individual plutons. The elongate, concordant Bonney, Denton, Cavendish, and Wheeler Plutons, which range in composition between monzodiorite and granodiorite, are the oldest relatively undeformed plutons in the Dry Valleys area. Each pluton is characterised by flow alignment of K-feldspar megacrysts, hornblende, biotite, and mafic enclaves. Field relationships and radiometric dating indicate these are deep-level plutons, emplaced synchronous with upper amphibolite facies metamorphism of the adjacent Koettlitz Group between 589 and 490 Ma ago. Elongate, discordant plutons of equigranular homogeneous biotite granodiorite and granite (Hedley, Valhalla, St Johns, Suess) were subsequently emplaced by stoping at a relatively high crustal level at 490 Ma. These eight plutons are cut by numerous swarms of Vanda mafic and felsic porphyry dikes. The ovoid, discordant, high level Pearse, Nibelungen, Orestes, Brownworth, Swinford, and Harker Plutons, emplaced between c. 486 and 477 Ma, display mutually crosscutting relationships with the youngest of the Vanda dikes. These younger plutons range in composition between monzonite and granite. Some are characterised by K-feldspar megacrystic textures superficially similar to some of the oldest concordant plutons. (author). 57 refs.; 2 tabs.; 4 figs

  5. Geological and 40Ar/39Ar age constraints on late-stage Deccan rhyolitic volcanism, inter-volcanic sedimentation, and the Panvel flexure from the Dongri area, Mumbai

    Science.gov (United States)

    Sheth, Hetu C.; Pande, Kanchan

    2014-04-01

    Post-K-Pg Boundary Deccan magmatism is well known from the Mumbai area in the Panvel flexure zone. Represented by the Salsette Subgroup, it shows characters atypical of much of the Deccan Traps, including rhyolite lavas and tuffs, mafic tuffs and breccias, spilitic pillow basalts, and "intertrappean" sedimentary or volcanosedimentary deposits, with mafic intrusions as well as trachyte intrusions containing basaltic enclaves. The intertrappean deposits have been interpreted as formed in shallow marine or lagoonal environments in small fault-bounded basins due to syn-volcanic subsidence. We report a previously unknown sedimentary deposit underlying the Dongri rhyolite flow from the upper part of the Salsette Subgroup, with a westerly tectonic dip due to the Panvel flexure. We have obtained concordant 40Ar/39Ar ages of 62.6 ± 0.6 Ma (2σ) and 62.9 ± 0.2 Ma (2σ) for samples taken from two separate outcrops of this rhyolite. The results are significant in showing that (i) Danian inter-volcanic sedimentary deposits formed throughout Mumbai, (ii) the rock units are consistent with the stratigraphy postulated earlier for Mumbai, (iii) shale fragments known in some Dongri tuffs were likely derived from the sedimentary deposit under the Dongri rhyolite, (iv) the total duration of extrusive and intrusive Deccan magmatism was at least 8-9 million years, and (v) Panvel flexure formed, or continued to form, after 63 Ma, possibly even 62 Ma, and could not have formed by 65-64 Ma as concluded in a recent study.

  6. Formation of a spatter-rich pyroclastic density current deposit in a Neogene sequence of trachytic-mafic igneous rocks at Mason Spur, Erebus volcanic province, Antarctica

    Science.gov (United States)

    Martin, A. P.; Smellie, J. L.; Cooper, A. F.; Townsend, D. B.

    2018-01-01

    Erosion has revealed a remarkable section through the heart of a volcanic island, Mason Spur, in the southwestern Ross Sea, Antarctica, including an unusually well-exposed section of caldera fill. The near-continuous exposure, 10 km laterally and > 1 km vertically, cuts through Cenozoic alkalic volcanic rocks of the Erebus volcanic province (McMurdo Volcanic Group) and permits the study of an ancient volcanic succession that is rarely available due to subsequent burial or erosion. The caldera filling sequence includes an unusual trachytic spatter-rich lapilli tuff (ignimbrite) facies that is particularly striking because of the presence of abundant black fluidal, dense juvenile spatter clasts of trachytic obsidian up to 2 m long supported in a pale cream-coloured pumiceous lapilli tuff matrix. Field mapping indicates that the deposit is an ignimbrite and, together with petrological considerations, it is suggested that mixing of dense spatter and pumiceous lapilli tuff in the investigated deposit occurred during emplacement, not necessarily in the same vent, with the mixed fragmental material emplaced as a pyroclastic density current. Liquid water was not initially present but a steam phase was probably generated during transport and may represent water ingested during passage of the current as it passed over either wet ground, stream, shallow lake or (possibly) snow. Well-exposed caldera interiors are uncommon and that at Mason Spur is helping understand eruption dynamics associated with a complex large island volcano. The results of our study should help to elucidate interpretations of other, less well exposed, pyroclastic density current deposits elsewhere in Antarctica and globally.

  7. Directional change during a Miocene R-N geomagnetic polarity reversal recorded by mafic lava flows, Sheep Creek Range, north central Nevada, USA

    Science.gov (United States)

    Bogue, S. W.; Glen, J. M. G.; Jarboe, N. A.

    2017-09-01

    Recurring transitional field directions during three Miocene geomagnetic reversals provide evidence that lateral inhomogeneity of the lower mantle affects flow in the outer core. We compare new paleomagnetic results from a composite sequence of 15.2 Ma lava flows in north central Nevada (Sheep Creek Range; 40.7°N, 243.2°E), erupted during a polarity reversal, to published data from Steens Mountain (250 km to the northwest in Oregon) and the Newberry Mountains (650 km to the south in California) that document reversals occurring millions of years and many polarity switches earlier. Alternating field demagnetization, followed by thermal demagnetization in half the samples, clearly isolated the primary thermoremanent magnetization of Sheep Creek Range flows. We correlated results from our three sampled sections to produce a composite record that begins with a single virtual geomagnetic pole (VGP) at low latitude in the Atlantic, followed by two VGPs situated near latitude 30°N in NE Africa. After jumping to 83°N (one VGP), the pole moves to equatorial South America (one VGP), back to NE Africa (three VGPs), to high southern latitudes (two VGPs), back to equatorial South America (three VGPs), and finally to high northern latitudes (nine VGPs). The repeated visits of the transitional VGP to positions in South America and near NE Africa, as well as the similar behavior recorded at Steens Mountain and the Newberry Mountains, suggest that lower mantle or core-mantle boundary features localize core flow structures, thereby imparting a discernible regional structure on the transitional geomagnetic field that persists for millions of years.

  8. Mechanical Mixing and Metamorphism of Mafic and Ultramafic Lithologies during Mylonisis at the ST. Paul Transform System, Mid-Atlantic Ridge

    Science.gov (United States)

    Adrião, Á.; Maia, M.; Hemond, C.; Kaczmarek, M. A.; Briais, A.; Vincent, C.; Brunelli, D.

    2017-12-01

    The St. Paul Transform System offsets by 630 km the Equatorial Mid Atlantic Ridge at 1° N. It consists of four major faults separating three intra transform ridge axes. This region shows a transition from a transpressive, hot spot affected, regional-scale shear zone to the North to a region dominated by a particular oceanic core complex spreading to the South (Vincent et al., this congress). Samples collected in the region during the COLMEIA cruise (Maia et al., 2016) were studied for textures and whole-rock major and trace element contents. All samples experienced pervasive deformation at ductile to brittle conditions overprinted by late low-T alteration. Mylonitic and ultramylonitic rocks can be grouped in three main types: peridotitic, gabbroic and talc-chlorite schist. Peridotitic ultramylonites preserve few opx, cpx and sp porphyroclasts; they have homogeneous nano-micro grain size groundmass, banded foliation and late amphibole and sulfide crystallization. Locally S-C fabric overprints the mylonitic texture. Micro cracks, filled with serpentine, chlorite and oxides are common, as well fluid inclusions trails in olivine and plagioclase crystals of peridotite and gabbros respectively. Major and trace element content of the peridotitic mylonites plot in the depleted field of the abyssal peridotites; however, they present marked LREE enrichment and Eu positive anomaly. Gabbroic and talc-chlorite mylonites display REE-enriched patterns (up to 100x CI) and variable Eu anomalies. Major elements show a remarkable linear trend in the talc-chlorite group suggesting mixing of pure talc and chlorite end-members. These compositional characteristics suggest variable assimilation of MORB and E-MORB during mylonisis or early melt-rock interaction and hydrothermal evolution at variable metamorphic conditions. Vincent et al., 2017. Particular Oceanic Core Complex evolution …; this congress Maia et al., 2016. Extreme mantle uplift and exhumation ... Nat. Geo. doi:10.1038/ngeo2759

  9. Origin of eclogite and garnet pyroxenite from the Moldanubian Zone of the Bohemian Massif, Czech Republic and its implication to other mafic layers embedded in orogenic peridotites

    Czech Academy of Sciences Publication Activity Database

    Obata, M.; Hirajima, T.; Svojtka, Martin

    2006-01-01

    Roč. 88, 1-2 (2006), s. 321-340 ISSN 0930-0708 R&D Projects: GA AV ČR IAA3013006 Institutional research plan: CEZ:AV0Z30130516 Keywords : eclogite * pyroxenite * Bohemian Massif Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.038, year: 2006

  10. Evidence for non-coaxiality of ferrimagnetic and paramagnetic fabrics, developed during magma flow and cooling in a thick mafic dyke

    Czech Academy of Sciences Publication Activity Database

    Silva, P. F.; Marques, F. O.; Machek, Matěj; Henry, B.; Hirt, A. M.; Roxerová, Zuzana; Madureira, P.; Vratislav, S.

    2014-01-01

    Roč. 629, August (2014), s. 155-164 ISSN 0040-1951 Institutional support: RVO:67985530 Keywords : paramagnetic * ferrimagnetic * fabrics * microstructures * dyke emplacement * stress field Subject RIV: DB - Geology ; Mineralogy Impact factor: 2.872, year: 2014

  11. Formation of thick stratiform Fe-Ti oxide layers in layered intrusion and frequent replenishment of fractionated mafic magma: Evidence from the Panzhihua intrusion, SW China

    Science.gov (United States)

    Song, Xie-Yan; Qi, Hua-Wen; Hu, Rui-Zhong; Chen, Lie-Meng; Yu, Song-Yue; Zhang, Jia-Fei

    2013-03-01

    Panzhihua intrusion is one of the largest layered intrusions that hosts huge stratiform Fe-Ti oxide layers in the central part of the Emeishan large igneous province, SW China. Up to 60 m thick stratiform massive Fe-Ti oxide layers containing 85 modal% of magnetite and ilmenite and overlying magnetite gabbro compose cyclic units of the Lower Zone of the intrusion. The cyclic units of the Middle Zone consist of magnetite gabbro and overlying gabbro. In these cyclic units, contents of Fe2O3(t), TiO2 and Cr and Fe3+/Ti4+ ratio of the rocks decrease upward, Cr content of magnetite and forsterite percentage of olivine decrease as well. The Upper Zone consists of apatite gabbro characterized by enrichment of incompatible elements (e.g., 12-18 ppm La, 20-28 ppm Y) and increasing of Fe3+/Ti4+ ratio (from 1.3 to 2.3) upward. These features indicate that the Panzhihua intrusion was repeatedly recharged by more primitive magma and evolved magmas had been extracted. Calculations using MELTS indicate that extensive fractionation of olivine and clinopyroxene in deep level resulted in increasing Fe and Ti contents in the magma. When these Fe-Ti-enriched magmas were emplaced along the base of the Panzhihua intrusion, Fe-Ti oxides became an early crystallization phase, leading to a residual magma of lower density. We propose that the unusually thick stratiform Fe-Ti oxide layers resulted from coupling of gravity settling and sorting of the crystallized Fe-Ti oxides from Fe-Ti-enriched magmas and frequent magma replenishment along the floor of the magma chamber.

  12. Effect of pressure on Fe3+/ΣFe ratio in a mafic magma and consequences for magma ocean redox gradients

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, H. L.; Hirschmann, M. M.; Cottrell, E.; Withers, A. C.

    2017-05-01

    Experiments establishing the effect of pressure on the Fe3+/ΣFe ratio of andesitic silicate melts buffered by coexisting Ru and RuO2 were performed from 100 kPa to 7 GPa and 1400–1750 °C. Fe3+/ΣFe ratios were determined by room temperature Mössbauer spectroscopy, but corrected for the effects of recoilless fraction. Fe3+/ΣFe ratios in quenched glasses decrease with increasing pressure consistent with previous results between 100 kPa and 3 GPa (O’Neill et al., 2006), but show only small pressure effects above 5 GPa. Ratios also decrease with increasing temperature. Mössbauer hyperfine parameters indicate mean coordination of Fe3+ ions of ~5 in glasses, with no dependence on the pressure from which the glasses were quenched, but show an increase with pressure in mean coordination of Fe2+ ions, from ~5 to ~6. XANES spectra on these glasses show variations in pre-edge intensities and centroid positions that are systematic with Fe3+/ΣFe, but are displaced from those established from otherwise identical andesitic glasses quenched at 100 kPa (Zhang et al., 2016). These systematics permit construction of a new XANES calibration curve relating pre-edge sub-peak intensities to Fe3+/ΣFe applicable to high pressure glasses. Consistent with interpretations of the Mössbauer hyperfine parameters, XANES pre-edge peak features in high pressure glasses are owing chiefly to the effects of pressure on the coordination of Fe2+ ions from ~5.5 to ~6, with negligible effects evident for Fe3+ ions. We use the new data to construct a thermodynamic model relating the effects of oxygen fugacity and pressure on Fe3+/ΣFe. We apply this model to calculate variations in oxygen fugacity in isochemical (constant Fe3+/ΣFe) columns of magma representative of magma oceans, in which fO2 is fixed at the base by equilibration with molten Fe. These calculations indicate that oxygen fugacities at the surface of shallow magma oceans are more reduced than at depth. For magma oceans in which the pressure at the base is near 5 GPa, as may be appropriate for Mercury and the Moon, conditions at the surface are ~1.5 log unit more reduced at the surface than at their base. If the results calibrated up to pressures of 7 GPa can be extrapolated to higher pressures appropriate for magma oceans on larger terrestrial planets such as Mars or Earth, then conditions at the surface are ~2 or 2.5 log units more reduced at the surface than at the base, respectively. Thus, atmospheres overlying shallow magma oceans should be highly reduced and rich in H2 and CO.

  13. New political violence in Africa : secular sectarianism in Sierra Leone

    NARCIS (Netherlands)

    Richards, P.

    1999-01-01

    Mary Douglas (1993) has indicated some of the shared concerns that keep voluntary enclaves together as 'social movements'. The present paper describes a rather different kind of enclave politics, being concerned with the 'new violence' of groups enclaved by social exclusion and force. The paper

  14. Primordial crustal growth in northern Nigeria: preliminary Rb-Sr and Sm-Nd constraints from Kaduna migmatite-gneiss complex

    International Nuclear Information System (INIS)

    Dada, S. S.; Briqueu, L.; Birck, J. L.

    1998-01-01

    The Kaduna Migmatite-Gneiss Complex in the central area of the Northern shield includes variably migmatised granitotrondhjemitic gneisses and amphibolite of hitherto unknown age. The amphibolite enclaves and dykes are metatholeiites with comparatively unfractionated rare-earth patterns. The two main rock units (TTG and amphibolite) exhibit complementary geochemical signatures in the normalised abundance patterns of relatively incompatible elements and suggest possible derivation of the gneisses from subduction related mafic material. Sm-Nd and Rb-Sr isotopic data document early Archaean crustal formation of new crust and its subsequent late Archaean differentiation. These preliminary results form an evidence for a more extended crustal history in the heart of the Pan-African domain (ca. 600 Ma.). They suggest the differentiation of juvenile crustal protolith from a chondritic reservoir about 3.5 Ga. for the gneiss-amphibolite bimodal suite. A tectonothermal event about 3.1-3.0 Ga led to the emplacement of an early gneiss as indicated from Rb-Sr and U-Ph zircon analyses. Subsequent differentiation and/or reworking around 2.8-2.7 Ga is coherent with the Liberian orogeny within the West African- Latino American subregion

  15. Petrographical and geochemical characterization and deformation conditions of the San Cristobal pluton, Sierra de Velasco, La Rioja, Argentina; Caracterizacion petrografica y geoquimica y condiciones de deformacion del pluton San Cristobal, Sierra de Velasco, La Rioja, Argentina

    Energy Technology Data Exchange (ETDEWEB)

    Bellos, L.I.; Toselli, A.J.; Rossi, J.N.; Grosse, P.; Rosa, J.D. de la; Castro, A.

    2010-07-01

    The San Cristobal pluton is a 35 km2 granitic body that outcrops at the southestern tip of the Sierra de Velasco, located west of La Rioja city, Argentina. It is formed by monzogranites and syenogranites, together with scarce granodiorites, with medium to fine-grained, equigranular to slightly porphyritic textures. Their mineral assemblage consists of quartz + microcline + plagioclase + biotite {+-} muscovite + zircon + apatite + magnetite. The granite contains dioritic to tonalitic mafic enclaves. The central and eastern parts of the granite have been deformed by the NNW-SSE trending South Mylonitic shear zone formed by mylonitic rocks. The metamorphic host-rock is represented by scarce greenschist facies xenoliths and hornfels with the high T/P assemblage K-feldspar - cordierite - biotite {+-} sillimanite. The granites are calc-alkaline, weak- to moderately peraluminous, and formed as part of a continental magmatic arc developed along the active margin of western Gondwana during the Early Paleozoic. The depth of emplacement of the San Cristobal pluton is estimated at {approx}12 km. (Author).

  16. Syn-collisional felsic magmatism and continental crust growth: A case study from the North Qilian Orogenic Belt at the northern margin of the Tibetan Plateau

    Science.gov (United States)

    Chen, Shuo; Niu, Yaoling; Xue, Qiqi

    2018-05-01

    The abundant syn-collisional granitoids produced and preserved at the northern Tibetan Plateau margin provide a prime case for studying the felsic magmatism as well as continental crust growth in response to continental collision. Here we present the results from a systematic study of the syn-collisional granitoids and their mafic magmatic enclaves (MMEs) in the Laohushan (LHS) and Machangshan (MCS) plutons from the North Qilian Orogenic Belt (NQOB). Two types of MMEs from the LHS pluton exhibit identical crystallization age ( 430 Ma) and bulk-rock isotopic compositions to their host granitoids, indicating their genetic link. The phase equilibrium constraints and pressure estimates for amphiboles from the LHS pluton together with the whole rock data suggest that the two types of MMEs represent two evolution products of the same hydrous andesitic magmas. In combination with the data on NQOB syn-collisional granitoids elsewhere, we suggest that the syn-collisional granitoids in the NQOB are material evidence of melting of ocean crust and sediment. The remarkable compositional similarity between the LHS granitoids and the model bulk continental crust in terms of major elements, trace elements, and some key element ratios indicates that the syn-collisional magmatism in the NQOB contributes to net continental crust growth, and that the way of continental crust growth in the Phanerozoic through syn-collisional felsic magmatism (production and preservation) is a straightforward process without the need of petrologically and physically complex processes.

  17. U-Pb (LA-ICPMS) zircon ages and Nd isotopes for granitoids of the Tamboril-Santa Quiteria Complex, Ceara Central Domain: implication for neoproterozoic syncollisional magmatism in north Borborema Province, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Felipe Grandjean da; Araujo, Carlos Eduardo Ganade de; Vasconcelos, Antonio Maurilio, E-mail: felipe.costa@cprm.gov.br, E-mail: caegeo@gmail.com, E-mail: maurilio.vasconcelos@cprm.gov.br [Servico Geologico do Brasil (CPRM), Fortaleza, CE (Brazil); Amaral, Wagner da Silva, E-mail: wamaral@ufc.br [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil). Departamento de Geologia; Rodrigues, Joseneusa Brilhante, E-mail: joseneusa.rodrigues@cprm.gov.br [Servico Geologico do Brasil (CPRM), Brasilia, DF (Brazil)

    2013-06-15

    The Tamboril-Santa Quiteria Complex (TSQC) is one of the largest Neoproterozoic plutonic manifestations in the north Borborema Province (NE Brazil). It represents an anatectic/igneous association characterized by a number of magmatic pulses that occurred in the 650-610 Ma interval. In this paper, we present U-Pb (LA-MC-ICP-MS) zircon ages and Nd isotopes for quartz monzonite and quartz diorites of the southern part of TSQC. The quartz monzonite belong to a hybrid granitoid association, including monzonite, syenites and quartz syenites, all with abundant mafic magmatic enclaves. A quartz monzonite sample yielded a U-Pb zircon age of 634 {+-} 10 Ma and a TDM age of 2.69 Ga. The quartz diorites are much more homogeneous in composition and yielded a U-Pb zircon age of 618 {+-} 23 Ma and a TDM age of 2.19 Ga. The presence of coeval mantle-derived magmatism and diatexites (crustal anatexis) post-dating high-pressure metamorphism (ca. 650 Ma), and together with high-temperature metamorphism (ca. 630-610 Ma), suggests that this large magmatic manifestation evolved in a collisional setting, probably related to slab break off during the Western Gondwana amalgamation. (author)

  18. Modeling soil organic matter (SOM) from satellite data using VISNIR-SWIR spectroscopy and PLS regression with step-down variable selection algorithm: case study of Campos Amazonicos National Park savanna enclave, Brazil

    Science.gov (United States)

    Rosero-Vlasova, O.; Borini Alves, D.; Vlassova, L.; Perez-Cabello, F.; Montorio Lloveria, R.

    2017-10-01

    Deforestation in Amazon basin due, among other factors, to frequent wildfires demands continuous post-fire monitoring of soil and vegetation. Thus, the study posed two objectives: (1) evaluate the capacity of Visible - Near InfraRed - ShortWave InfraRed (VIS-NIR-SWIR) spectroscopy to estimate soil organic matter (SOM) in fire-affected soils, and (2) assess the feasibility of SOM mapping from satellite images. For this purpose, 30 soil samples (surface layer) were collected in 2016 in areas of grass and riparian vegetation of Campos Amazonicos National Park, Brazil, repeatedly affected by wildfires. Standard laboratory procedures were applied to determine SOM. Reflectance spectra of soils were obtained in controlled laboratory conditions using Fieldspec4 spectroradiometer (spectral range 350nm- 2500nm). Measured spectra were resampled to simulate reflectances for Landsat-8, Sentinel-2 and EnMap spectral bands, used as predictors in SOM models developed using Partial Least Squares regression and step-down variable selection algorithm (PLSR-SD). The best fit was achieved with models based on reflectances simulated for EnMap bands (R2=0.93; R2cv=0.82 and NMSE=0.07; NMSEcv=0.19). The model uses only 8 out of 244 predictors (bands) chosen by the step-down variable selection algorithm. The least reliable estimates (R2=0.55 and R2cv=0.40 and NMSE=0.43; NMSEcv=0.60) resulted from Landsat model, while Sentinel-2 model showed R2=0.68 and R2cv=0.63; NMSE=0.31 and NMSEcv=0.38. The results confirm high potential of VIS-NIR-SWIR spectroscopy for SOM estimation. Application of step-down produces sparser and better-fit models. Finally, SOM can be estimated with an acceptable accuracy (NMSE 0.35) from EnMap and Sentinel-2 data enabling mapping and analysis of impacts of repeated wildfires on soils in the study area.

  19. LOS CASINOS EN CHILE COMO ENCLAVES TURÍSTICOS-REGIONALES: APORTES Y ASIMETRÍAS DE RENDICIÓN DE CUENTAS / CASINOS IN CHILE AS TOURIST-REGIONAL SPOTS: CONTRIBUTIONS AND ASYMMETRIES OF RESPONSIBILITY

    Directory of Open Access Journals (Sweden)

    Ignacio Cienfuegos

    2017-12-01

    Full Text Available The following article explains the contributions of the Chilean casino industry to the regional development and the municipal rents which, from 2005. It shows the median contribution of these companies to the regional rents of a country with a centralized form of government, but significant for the municipalities of the regions closed to Santiago. Also, it reveals the creation of direct employment and the benefits it brings to new hotels and for the access to shows in regions with deficient touristic development. The analysis of interviews to local actors, located in the southern central zone, corroborated that, along with the assessment to infrastructure and incomes, the industry is criticized due to the scant coordination between public regional and municipal agencies in the generation of touristic clusters. Some recommendations are made for the Chilean case in terms of improving tax collections, achieving convergence in relation to municipal contributions and enhancing accountability and its impact towards touristic-productive dynamism.

  20. Multi-Criteria GIS Methodology Focused on the Location of Optimal Places for Small Hydro Power Via Hydrological and Geostatistic Aplications; Metodologia SIG Multicriterio Enfocada a la Localizacion de Enclaves Optimos para Centrales de Minihidroelectricas mediante Aplicaciones Hidrologicas y Geoestadisticas

    Energy Technology Data Exchange (ETDEWEB)

    Paz, C de la

    2013-02-01

    The main objective of this research is the development of a location methodology for sitting optimization of small hydro power (SHP) centrals. In order of achieve this goal, a Multi-Criteria Evaluation (MCE) methodology implemented through the use of tools in a GIS environment: Spatial Analysis, Geostatistic Analysis, and Hydrology have been developed. This methodology includes two different models based on the same MCE process. The substantial difference of both models is in the input data and the tools applied to estimate the energy resource and the principal factor of the methodology (caudal or accumulated flow). The first model is generated from caudal data obtained in the study area (El Bierzo), and the second one from pluviometric data and Digital Terrain Model (DTM). Both models include viability maps with greater ability areas to locate SHP facilities. As an additional objective, the study allows contrasting the results of the two developed models to evaluate their similarity. (Author)

  1. Caracterización petrográfica y geoquímica y condiciones de deformación del plutón San Cristóbal, Sierra de Velasco (La Rioja, Argentina

    Directory of Open Access Journals (Sweden)

    Bellos, L. I.

    2010-12-01

    Full Text Available The San Cristóbal pluton is a 35 km2 granitic body that outcrops at the southestern tip of the Sierra de Velasco, located west of La Rioja city, Argentina. It is formed by monzogranites and syenogranites, together with scarce granodiorites, with medium to fine-grained, equigranular to slightly porphyritic textures. Their mineral assemblage consists of quartz + microcline + plagioclase + biotite ± muscovite + zircon + apatite + magnetite. The granite contains dioritic to tonalitic mafic enclaves. The central and eastern parts of the granite have been deformed by the NNW-SSE trending South Mylonitic shear zone formed by mylonitic rocks. The metamorphic host-rock is represented by scarce greenschist facies xenoliths and hornfels with the high T / P assemblage K-feldspar - cordierite - biotite ± sillimanite. The granites are calc-alkaline, weak- to moderately peraluminous, and formed as part of a continental magmatic arc developed along the active margin of western Gondwana during the Early Paleozoic. The depth of emplacement of the San Cristóbal pluton is estimated at ~12 km.

    El plutón San Cristóbal constituye un cuerpo granítico de 35 km2 que aflora en el extremo sudeste de la Sierra de Velasco, situada al oeste de la ciudad de La Rioja, Argentina. Está formado por monzogranitos y sienogranitos con escasas granodioritas, de texturas equigranulares de grano medio a fino a ligeramente porfíricas. La asociación mineral es cuarzo + microclino + plagioclasa + biotita ± moscovita + circón + apatito + magnetita. Contiene enclaves magmáticos máficos de composición diorítica a tonalítica. El granito fue afectado en su parte media y este por una zona de cizalla, formada por milonitas que integran la Faja Milonítica Sur, de rumbo NNO-SSE. La roca de caja se reconoce por xenolitos de esquistos y cuarcitas en facies esquistos verdes, y septos de corneanas con la paragénesis feldespato potásico cordierita

  2. Short-circuiting magma differentiation from basalt straight to rhyolite?

    Science.gov (United States)

    Ruprecht, P.; Winslow, H.

    2017-12-01

    Silicic magmas are the product of varying degrees of crystal fractionation and crustal assimilation/melting. Both processes lead to differentiation that is step-wise rather than continuous for example during melt separation from a crystal mush (Dufek and Bachmann, 2010). However, differentiation is rarely efficient enough to evolve directly from a basaltic to a rhyolitic magma. At Volcán Puyehue-Cordón Caulle, Chile, the magma series is dominated by crystal fractionation where mixing trends between primitive and felsic end members in the bulk rock compositions are almost absent (e.g. P, FeO, TiO2 vs. SiO2). How effective fraction is in this magmatic system is not well-known. The 2011-12 eruption at Cordón Caulle provides new constraints that rhyolitic melts may be derived directly from a basaltic mush. Minor, but ubiquitous mafic, crystal-rich enclaves co-erupted with the predominantly rhyolitic near-aphyric magma. These enclaves are among the most primitive compositions erupted at Puyehue-Cordón Caulle and geochemically resemble closely basaltic magmas that are >10 ka old (Singer et al. 2008) and that have been identified as a parental tholeiitic mantle-derived magma (Schmidt and Jagoutz, 2017) for the Southern Andean Volcanic Zone. The vesiculated nature, the presence of a microlite-rich groundmass, and a lack of a Eu anomaly in these encalves suggest that they represent recharge magma/mush rather than sub-solidus cumulates and therefore have potentially a direct petrogenetic link to the erupted rhyolites. Our results indicate that under some conditions crystal fractionation can be very effective and the presence of rhyolitic magmas does not require an extensive polybaric plumbing system. Instead, primitive mantle-derived magmas source directly evolved magmas. In the case, of the magma system beneath Puyehue-Cordón Caulle, which had three historic rhyolitic eruptions (1921-22, 1960, 2011-12) these results raise the question whether rhyolite magma extraction

  3. Magmatism and polymetallic mineralization in southwestern Qinzhou-Hangzhou metallogenic belt, South China

    Science.gov (United States)

    Huang, Xudong; Lu, Jianjun; Wang, Rucheng; Ma, Dongsheng

    2016-04-01

    As Neoproterozoic suture zone between the Yangtze Block and Cathaysia Block, Qinzhou-Hangzhou metallogenic belt is one of the 21 key metallogenic belts in China. Intensive multiple-aged felsic magmatism and related polymetallic mineralization take place in this belt. Although Neoproterozoic, Paleozoic, Triassic granites and associated deposits have been found in southwestern Qinzhou-Hangzhou metallogenic belt, Middle-Late Jurassic (150-165 Ma) magmatism and related mineralization is of the most importance. Three major kinds of Middle-Late Jurassic granitoids have been distinguished. (Cu)-Pb-Zn-bearing granitoids are slightly differentiated, calc-alkaline and metaluminous dioritic to granodioritic rocks. Sn-(W)-bearing granites contain dark microgranular enclaves and have high contents of REE and HFSE, suggesting affinities of aluminous A-type (A2) granites. W-bearing granites are highly differentiated and peraluminous rocks. (Cu)-Pb-Zn-bearing granitoids have ɛNd(t) values of -11 ˜ -4 and ɛHf(t) values of -12 ˜ -7, corresponding to TDMC(Nd) from 1.4 to 1.8 Ga and TDMC(Hf) from 1.6 to 2.0 Ga, respectively. The ɛNd(t) values of W-bearing granites vary from -11 to -8 with TDMC(Nd) of 1.6 ˜ 1.9 Ga and ɛHf(t) values change from -16 to -7 with TDMC(Hf) of 1.5 ˜ 2.0 Ga. Compared with (Cu)-Pb-Zn-bearing granitoids and W-bearing granites, the Sn-(W)-bearing granites have higher ɛNd(t) (-8 ˜ -2) and ɛHf(t) (-8 ˜ -2) values and younger TDMC(Nd) (1.1 ˜ 1.6 Ga) and TDMC(Hf) (1.2 ˜ 1.8 Ga) values, showing a more juvenile isotopic character. Sn-(W)-bearing granites originate from partial melting of granulitized lower crust involved with some mantle-derived materials. W-bearing granites are derived from partial melting of crust. (Cu)-Pb-Zn-bearing granitoids are also derived from crust but may be influenced by more mantle-derived materials. For (Cu)-Pb-Zn deposits, skarn and carbonate replacement are the most important mineralization types. Cu ore bodies mainly

  4. Geochemistry of biotite granites from the Lamas de Olo Pluton, northern Portugal

    Science.gov (United States)

    Fernandes, Susana; Gomes, Maria; Teixeira, Rui; Corfu, Fernando

    2013-04-01

    In the Central Iberian Zone (CIZ) extensive crustal recycling occurred during the post-thickening extension stage of the Variscan orogeny (~330-290 Ma). After the ductile deformation phase D3 (~320-300 Ma), characterized by the intrusion of large volumes of highly peraluminous granitic magmas, rapid and drastic tectonic changes at about 300 Ma gave rise to the brittle phase of deformation D4 that controlled the emplacement of Fe-K subalkaline granites (296-290 Ma; Dias et al. 1998). The Lamas de Olo Pluton (LOP) is controlled by NE-SW and NW-SE fracture systems, probably related to the Régua-Verin fault zone (Pereira, 1989). The LOP is a medium to coarse-grained, porphyritic biotite granite, accompanied by medium- to fine grained, porphyritic biotite granite (Alto dos Cabeços- AC) and a more leucocratic, fine-grained, slightly porphyritic biotite-muscovite granite (Barragens- BA). The contacts between LO and AC are generally diffuse, whereas those to BA are sharp. In fact, the BA granite can occur in dykes and sills cutting LO and AC. Microgranular enclaves and xenoliths are very rare. The LOP intrudes the Douro Group, presumably of Precambrian to Cambrian age, and two-mica granites from the Vila Real composite massif. The LOP granites consist of quartz, microcline, plagioclase, biotite, zircon, titanite, tourmaline apatite, fluorite, ilmenite, magnetite, and rutile, with muscovite in BA granite and rare allanite in the LO and AC granites. The plagioclase composition is of oligoclase (An12) - andesine (An35) for LO granite, albite (An9) - andesine (An30) for CA granite and albite (An5) - oligoclase (An20) for BA granite. There are decreases in: a) anorthite content from phenocryst to matrix plagioclase; b) Ba content from phenocryst to matrix microcline in all granites. The Fe2+ biotite has a composition similar to that of biotite from calc-alkaline to sub-alkaline rock series. The LO and AC granites are meta- to peraluminous with ASI variable between 1.05 and 1

  5. Granitoides paleozoicos de la Sierra de Narváez, Sistema de Famatina, Argentina: Hibridización de magmas en un margen continental activo

    Directory of Open Access Journals (Sweden)

    Cisterna, C. E.

    1992-12-01

    Full Text Available The granitoids from the Sierra de Narváez were investigated for their geochemical and petrographical characteristics. They are composed of calc-alkaline granites, granodiorites and tonalites, similar to the other paleozoic granitoids of the Famatina System. These rocks are intrusive in the Las Planchadas (volcanic rocks and Suri (sedimentary rocks Formations, which are probably cogenetic with the granitoids within the same magmatic cycle.The study of the granitoids reveals the close relationship between their composition and the abundance of the enclosed magmatic inclusions. The latter represent rocks and granodioritic tonalitic and diorite composition, and have a great number of mineralogical characteristic that suggest the presence of two magmas, mafic and felsic for the origin of such enclaves.The close chemical relationship existing between the inclusions and their host rocks shows that the mafic and felsic components are compositionally modified and that the granitoids are more or less hybridized.Trace elements discrimination diagrams have been used as a tools for fingerprinting the tectonic setting of the Sierra de Narváez granitoids. The geochemistry as well as the geologic relations of the granitoids with the roughly coeval ordovician vulcanism indicate a volcanic arc environment.Las rocas que afloran en el extremo septentrional de la Sierra de Narváez están representadas por una asociación de monzogranitos, granodioritas y tonalitas que definen una serie calcoalcalina, de características similares a las de otros intrusivos del Paleozoico del Sistema de Famatina. Estos granitoides se hallan intruyendo las Formaciones Las Planchadas y Suri, representadas por vulcanitas y metasedimentitas, respectivamente, y corresponderían a un mismo evento magmático del Paleozoico Inferior.Los granitoides estudiados presentan abundantes inclusiones ígneas de composición granodiorítica o tonalítica y diorítica. La estrecha relación que

  6. 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

  7. Consequences of magma eruption dynamics: Intraflow variations in petrography and mineral chemistry within a single eruptive unit from Whitewater Canyon, Oregon

    Science.gov (United States)

    Ustunisik, G. K.; Nielsen, R. L.

    2012-12-01

    Individual lava flows are sometimes characterized by progressive changes in petrography and mineral chemistry which have been attributed to progressive magma chamber evacuation. In the case of Whitewater Canyon flow, a glacially quenched andesite unit on the NW flank of Mt. Jefferson, significant changes have been observed in phenocryst content and mineral chemistry within a transect from the early erupted components (inferred by flow morphology to be quenched against glacial ice ~10000 ybp), to the top of the 30 m thick flow unit. With the increasing distance from the quenched interface, the matrix changes from glassy to microcrystalline. The matrix material is generally similar in composition to the glassy melt inclusions rhyolitic in composition yet relatively degassed (lower Cl, S). Based on their morphology, we have identified at least 4 populations of plagioclase phenocrysts within the single flow: (1) Relatively unzoned high An cores (>An80) with oscillatory overgrowth, (2) Lower An cores (An50-60), associated with dacitic melt inclusions, (3) Cellular low An cores (An50-60) with higher An overgrowths (~An65-75), and (4) Lath shaped, sometimes oscillatory zoned moderately high An phenocrysts (An65-75) -often associated with olivine:cpx:plagioclase glomerocrysts. Melt inclusions are present in orthopyroxene and plagioclase, but only in the earliest erupted samples (within 5-10 meters of the quenched interface). This mafic component, characterized by olivine, intermediate plagioclase (An60-75), clinopyroxene, orthopyroxene, and oxides, was present at a range of scales from glomerocrysts to 10 cm+ enclaves. Amphibole and quartz are present only in samples from the interior of the flow unit. The width of reaction rims on amphibole increase as one progress upwards towards the flow interior. Our initial conclusions are this eruptive unit represents the progressive evacuation of a shallow magma chamber where the upper parts of the chamber had already been partially

  8. Geochemistry of the Serifos calc-alkaline granodiorite pluton, Greece: constraining the crust and mantle contributions to I-type granitoids

    Science.gov (United States)

    Stouraiti, C.; Baziotis, I.; Asimow, P. D.; Downes, H.

    2017-11-01

    The Late Miocene (11.6-9.5 Ma) granitoid intrusion on the island of Serifos (Western Cyclades, Aegean Sea) is composed of syn- to post-tectonic granodiorite with quartz monzodiorite enclaves, cut by dacitic and aplitic dikes. The granitoid, a typical I-type metaluminous calcic amphibole-bearing calc-alkaline pluton, intruded the Cycladic Blueschists during thinning of the Aegean plate. Combining field, textural, geochemical and new Sr-Nd-O isotope data presented in this paper, we postulate that the Serifos intrusion is a single-zoned pluton. The central facies has initial 87Sr/86Sr = 0.70906 to 0.7106, ɛNd(t) = - 5.9 to - 7.5 and δ18Οqtz = + 10 to + 10.6‰, whereas the marginal zone (or border facies) has higher initial 87Sr/86Sr = 0.711 to 0.7112, lower ɛ Nd(t) = - 7.3 to - 8.3, and higher δ18Οqtz = + 10.6 to + 11.9‰. The small range in initial Sr and Nd isotopic values throughout the pluton is paired with a remarkable uniformity in trace element patterns, despite a large range in silica contents (58.8 to 72 wt% SiO2). Assimilation of a crustally derived partial melt into the mafic parental magma would progressively add incompatible trace elements and SiO2 to the evolving mafic starting liquid, but the opposite trend, of trace element depletion during magma evolution, is observed in the Serifos granodiorites. Thermodynamic modeling of whole-rock compositions during simple fractional crystallization (FC) or assimilation-fractional crystallization (AFC) processes of major rock-forming minerals—at a variety of pressure, oxidation state, and water activity conditions—fails to reproduce simultaneously the major element and trace element variations among the Serifos granitoids, implying a critical role for minor phases in controlling trace element fractionation. Both saturation of accessory phases such as allanite and titanite (at SiO2 ≥ 71 wt%)(to satisfy trace element constraints) and assimilation of partial melts from a metasedimentary component (to

  9. Postorogenic emplacement of the Santa Marta Batholith, northwestern flank of the Sierra Nevada de Santa Marta (SNSM).

    Science.gov (United States)

    Sanchez Sierra, Johan Miguel Sebastian; Kammer, Andreas

    2017-04-01

    The Santa Marta Batholith (BSM) belongs to a Paleogene intrusive suite of the Santa Marta massif, an exhumed triangular block at the southern Caribbean margin. Its Paleogene age precludes its association to an active margin, although its emplacement was controlled by the flexure of the down-bent Southamerican plate. Its internal structure is outlined by a mafic border facies and a felsic core, both having a petrologic affinity to a TTG-suite. According to existing age data, the BSM consolidated sequentially from SW to NE, with a first pulse having crystallized at 56 Ma in the southern domain and a final pulse in the northern domain at 52-50 Ma. Pressures varied between 5-7 kb, corresponding to depths of 14-19 km. This study combines structural, thermochronological and geochemical data with an analysis of Anisotropy and Magnetic Susceptibility (AMS) and paleomagnetism. The SNSM had a clockwise rotation of 30 ° and the ASM results help distinguish between two fault-bounded structural domains. The southern domain is characterized by a magnetic foliation concordant to the contact of the host rock that dips toward the hinterland. The northern domain, in contrast, displays a N-S trending magnetic foliation that is oblique to the regional structural northeastern trend. This divergence is supported by the orientation of mineral lineations, enclaves and dikes. In spite of its arc signature, anomalies like enrichment in Ti, depletion of Nb-Ta and Zr-Hf, as well as flat REE patterns can be associated to the accumulation of crystallized mafic minerals from less-fractionated magmas. These data evidence mingling. Asymmetric internal organization, as indicated by a hinterland-dipping roof pendent, the structural setting at the margin of a thickened continental margin and its geochemical signature favor a scenario of a magma generation at a mid-crustal level and its consequent extrusion along a channel, that connected to the crustal bend of the continental plate that was

  10. The Late Cretaceous Middle Fork caldera, its resurgent intrusion, and enduring landscape stability in east-central Alaska

    Science.gov (United States)

    Bacon, Charles R.; Dusel-Bacon, Cynthia; Aleinikoff, John N.; Slack, John F.

    2014-01-01

    Dissected caldera structures expose thick intracaldera tuff and, uncommonly, cogenetic shallow plutons, while remnants of correlative outflow tuffs deposited on the pre-eruption ground surface record elements of ancient landscapes. The Middle Fork caldera encompasses a 10 km × 20 km area of rhyolite welded tuff and granite porphyry in east-central Alaska, ∼100 km west of the Yukon border. Intracaldera tuff is at least 850 m thick. The K-feldspar megacrystic granite porphyry is exposed over much of a 7 km × 12 km area having 650 m of relief within the western part of the caldera fill. Sensitive high-resolution ion microprobe with reverse geometry (SHRIMP-RG) analyses of zircon from intracaldera tuff, granite porphyry, and outflow tuff yield U-Pb ages of 70.0 ± 1.2, 69.7 ± 1.2, and 71.1 ± 0.5 Ma (95% confidence), respectively. An aeromagnetic survey indicates that the tuff is reversely magnetized, and, therefore, that the caldera-forming eruption occurred in the C31r geomagnetic polarity chron. The tuff and porphyry have arc geochemical signatures and a limited range in SiO2 of 69 to 72 wt%. Although their phenocrysts differ in size and abundance, similar quartz + K-feldspar + plagioclase + biotite mineralogy, whole-rock geochemistry, and analytically indistinguishable ages indicate that the tuff and porphyry were comagmatic. Resorption of phenocrysts in tuff and porphyry suggests that these magmas formed by thermal rejuvenation of near-solidus or solidified crystal mush. A rare magmatic enclave (54% SiO2, arc geochemical signature) in the porphyry may be similar to parental magma and provides evidence of mafic magma and thermal input.

  11. Rare Earth Element Behaviour in Apatite from the Olympic Dam Cu–U–Au–Ag Deposit, South Australia

    Directory of Open Access Journals (Sweden)

    Sasha Krneta

    2017-08-01

    Full Text Available Apatite is a common magmatic accessory in the intrusive rocks hosting the giant ~1590 Ma Olympic Dam (OD iron-oxide copper gold (IOCG ore system, South Australia. Moreover, hydrothermal apatite is a locally abundant mineral throughout the altered and mineralized rocks within and enclosing the deposit. Based on compositional data for zoned apatite, we evaluate whether changes in the morphology and the rare earth element and Y (REY chemistry of apatite can be used to constrain the fluid evolution from early to late hydrothermal stages at OD. The ~1.6 Ga Roxby Downs granite (RDG, host to the OD deposit, contains apatite as a magmatic accessory, locally in the high concentrations associated with mafic enclaves. Magmatic apatite commonly contains REY-poor cores and REY-enriched margins. The cores display a light rare earth element (LREE-enriched chondrite-normalized fractionation pattern with a strong negative Eu anomaly. In contrast, later hydrothermal apatite, confined to samples where magmatic apatite has been obliterated due to advanced hematite-sericite alteration, displays a conspicuous, convex, middle rare earth element (MREE-enriched pattern with a weak negative Eu anomaly. Such grains contain abundant inclusions of florencite and sericite. Within high-grade bornite ores from the deposit, apatite displays an extremely highly MREE-enriched chondrite-normalized fractionation trend with a positive Eu anomaly. Concentrations of U and Th in apatite mimic the behaviour of ∑REY and are richest in magmatic apatite hosted by RDG and the hydrothermal rims surrounding them. The shift from characteristic LREE-enriched magmatic and early hydrothermal apatite to later hydrothermal apatite displaying marked MREE-enriched trends (with lower U, Th, Pb and ∑REY concentrations reflects the magmatic to hydrothermal transition. Additionally, the strong positive Eu anomaly in the MREE-enriched trends of apatite in high-grade bornite ores are attributable to

  12. Magmatic emulsion texture formed by mixing during extrusion, Rauðafell composite complex, Breiðdalur volcano, eastern Iceland

    Science.gov (United States)

    Charreteur, Gilles; Tegner, Christian

    2013-06-01

    The Rauðafell composite complex is part of the Neogene Breiðdalur volcano, eastern Iceland and is composed of a composite feeder dyke, a vent structure and a composite flow. The two end-members of the composite complex are rhyolite and basalt, and both are rich in plagioclase macrocrysts: bytownite in basalt and oligoclase in rhyolite. The rhyolite also includes ferroaugite macrocrysts. The mixed rocks are separated in three textural groups related to mixing proportions. When the basaltic end-member is dominant, a hybrid texture with a homogeneous matrix is observed and the only evidence of mixing is the presence of antecrysts of both end-members. When the basaltic end-member represents c. 65 to 30 % of the mixture, we observe emulsion textures composed of finely co-mingled basalt and rhyolite. The difference between these two textural expressions of mixing is due to effects of diffusion. The third texture shows mafic enclaves suspended in a rhyolitic matrix. In these rocks, the proportion of the basaltic end-member is inferior to 30 %, implying that the basalt froze solid in contact with the rhyolite. Zoning of plagioclase shows that the mixing processes are driven initially by highly efficient micro-mingling; the emulsification is possibly a result of compositional gradient stresses (Korteweg stress) between miscible basalt and rhyolite. This is followed by chemical diffusion (hybridisation) and tend to protect antecrysts from reaction with the primitive magmas. When antecrysts originated in the evolved magma, they undergo dissolution due to thermal disequilibrium during mingling and chemical disequilibrium during hybridisation. We argue that such mixing processes are important in producing intermediate rocks in Iceland and elsewhere that shows only the chemical attributes of an origin by mixing. The preservation of emulsion textures is rare and highly dependent on cooling history.

  13. Magmatic structures in the Krkonoše Jizera Plutonic Complex, Bohemian Massif: evidence for localized multiphase flow and small-scale thermal mechanical instabilities in a granitic magma chamber

    Science.gov (United States)

    Žák, Jiří; Klomínský, Josef

    2007-08-01

    The present paper examines magmatic structures in the Jizera and Liberec granites of the Krkonoše-Jizera Plutonic Complex, Bohemian Massif. The magmatic structures are here interpreted to preserve direct field evidence for highly localized magma flow and other processes in crystal-rich mushes, and to capture the evolution of physical processes in an ancient granitic magma chamber. We propose that after chamber-wide mixing and hybridization, as suggested by recent petrological studies, laminar magma flow became highly localized to weaker channel-like domains within the higher-strength crystal framework. Mafic schlieren formed at flow rims, and their formation presumably involved gravitational settling and velocity gradient flow sorting coupled with interstitial melt escape. Local thermal or compositional convection may have resulted in the formation of vertical schlieren tubes and ladder dikes whereas subhorizontal tubes or channels formed during flow driven by lateral gradients in magma pressure. After the cessation or deceleration of channel flow, gravity-driven processes (settling of crystals and enclaves, gravitational differentiation, development of downward dripping instabilities), accompanied by compaction, filter pressing and melt segregation, dominated in the crystal mush within the flow channels. Subsequently, magmatic folds developed in schlieren layers and the magma chamber recorded complex, late magmatic strains at high magma crystallinities. Late-stage magma pulsing into localized submagmatic cracks represents the latest events of magmatic history of the chamber prior to its final crystallization. We emphasize that the most favorable environments for the formation and preservation of magmatic structures, such as those hosted in the Jizera and Liberec granites, are slowly cooling crystal-rich mushes. Therefore, where preserved in plutons, these structures may lend strong support for a "mush model" of magmatic systems.

  14. Origin, Petrogenesis and radiometric age dating of Pichagchi Batholith (North West Iran)

    International Nuclear Information System (INIS)

    Kholghi, M.H.; Vossoughi Abedini, A.

    2004-01-01

    Pichagchi batholith, located in 35 Km southeast of Shahin Dez, northwest of Iran, is situated in Central Iran, cutting Paleozoic rocks. Absolute age determination for this batholith by K-Ar radiometric method gives 74.20 Ma. indicating Late Cretaceous-Paleocene time corresponding to lauramide orogeny. This batholith consists of quartz diorite, tonalite, granodiorite and quartz monzodiorite in which main mafic minerals are biotite and amphibole. Enclaves are mica schist and fine graind quartz diorite in various sizes. Sieve texture and zonation observed in plagioclase minerals indicate that the original magma has been produced by magma mixing of lower crust and upper mantle. Geochemistry study of the main elements shows that the batholith is calc-alkaline and meta luminous and A12O3, Na2O, K2O, FeO values are high where as MgO, CaO, MnO, P2O5, TiO2 are low. In addition, genetic parameters for this batholith is compatible with I-Type granites (Caledonian). Rare earth elements plotted in spider diagrams show that the average slope the curves is from K towards Cr (left to right), indicating partial melting. Depletion of compatible elements such as Ni, Cu, V and enrichment of incompatible elements imply that magma was not original and not initiated from mantle. Further mores trough of Nb could be interpreted by magma mixing with crustal materials or by subduction. Also trough of Ti and crest of Y elements show that the origin of the magma is I-type. Finally, Pichagchi batholith is orogenic and its tectonic setting is compatible with continental arc granitoids

  15. Présence d'un magmatisme d'âge Viséen moyen dans le versant sud du massif du Pilat, Massif central oriental; conséquences

    Science.gov (United States)

    Duthou, Jean-Louis; Chenevoy, Maurice; Gay, Marc

    1998-12-01

    Dating of a microgranular granite, which intrudes the granito-migmatitic complex linked to the Velay Upper Carboniferous granite, gives a Middle Visean age (342 Ma). The relationships between these various granites and the low pressure metamorphic series from Pilat are re-examined.

  16. Evidence for, and consequences of, middle Visean magmatism on the south side of the Pilat Massif, eastern French Massif Central

    International Nuclear Information System (INIS)

    Duthou, J.L.; Chenevoy, M.; Gay, M.

    1998-01-01

    Dating of a micro-granular granite, which intrudes the granitic-migmatitic complex linked to the Velay Upper Carboniferous granite, gives a Middle age (342 Ma). The relationships between these various granites and the low pressure metamorphic series from Pilat are re-examined. (authors)

  17. Tribological properties of rice starch in liquid and semi-solid food model systems

    NARCIS (Netherlands)

    Liu, K.; Stieger, M.A.; Linden, van der E.; Velde, van de Fred

    2016-01-01

    This study investigated the tribological and rheological properties of liquid and semi-solid food model systems containing micro-granular rice starch. Native (uncooked) and gelatinized rice starch dispersions, o/w emulsions and emulsion-filled gelatin gels were studied as food model systems. Native

  18. Solubility of platinum-arsenide melt and sperrylite in synthetic basalt at 0.1 MPa and 1200 °C with implications for arsenic speciation and platinum sequestration in mafic igneous systems

    Science.gov (United States)

    Canali, A. C.; Brenan, J. M.; Sullivan, N. A.

    2017-11-01

    To better understand the Pt-As association in natural magmas, experiments were done at 1200 °C and 0.1 MPa to measure the solubility of Pt and Pt-arsenide phases (melt and sperrylite, PtAs2), as well as to determine the oxidation state, and identify evidence for Pt-As complexing, in molten silicate. Samples consisting of synthetic basalt contained in chromite crucibles were subject to three experimental procedures. In the first, platinum solubility in the synthetic basalt was determined without added arsenic by equilibrating the sample with a platinum source (embedded wire or bead) in a gas-mixing furnace. In the second, the sample plus a Pt-arsenide source was equilibrated in a vacuum-sealed fused quartz tube containing a solid-oxide oxygen buffer. The third approach involved two steps: first equilibrating the sample in a gas-mixing furnace, then with added arsenide melt in a sealed quartz tube. Oxygen fugacity was estimated in the latter step using chromite/melt partitioning of vanadium. Method two experiments done at high initial arsenic activity (PtAs melt + PtAs2), showed significant loss of arsenic from the sample, the result of vapour transfer to newly-formed arsenide phases in the buffer. Method three experiments showed no loss of arsenic, yielding a uniform final distribution in the sample. Analyses of run-product glasses from experiments which did not show arsenic loss reveal significant increase in arsenic concentrations with fO2, varying from ∼10 ppm (FMQ-3.25) to >10,000 ppm (FMQ + 5.5). Despite very high arsenic loadings (>1000 ppm), the solubility of Pt is similar in arsenic-bearing and arsenic-free glasses. The variation in arsenic solubility with fO2 shows a linear relationship, that when corrected for the change in the activity of dissolved arsenic with the melt ferric/ferrous ratio, yields a solubility-fO2 relationship consistent with As3+ as the dissolved species. This result is confirmed by X-ray absorption near edge structure (XANES) determination on run-product glasses. Levels of arsenic required for Pt-arsenide saturation are 50-500 ppm over the fO2 range of most terrestrial basalts (FMQ to FMQ-2), >100× higher than the arsenic concentrations typical of such magmas, indicating significant enrichment of arsenic is required if Pt-arsenide saturation is to occur. In contrast, the level of dissolved Pt required to saturate in sperrylite is >8× lower than for pure Pt, suggesting that arsenic enrichment could lead to Pt removal at concentrations much less than required for pure metal saturation.

  19. Petrology and geochemistry of mafic magmatic rocks from the Sarve-Abad ophiolites (Kurdistan region, Iran): Evidence for interaction between MORB-type asthenosphere and OIB-type components in the southern Neo-Tethys Ocean

    Science.gov (United States)

    Saccani, Emilio; Allahyari, Khalil; Rahimzadeh, Bahman

    2014-05-01

    The Sarve-Abad (Sawlava) ophiolites crop out in the Main Zagros Thrust Zone and represent remnants of the Mesozoic southern Neo-Tethys Ocean that was located between the Arabian shield and Sanandaj-Sirjan continental block. They consist of several incomplete ophiolitic sequences including gabbroic bodies, a dyke complex, and pillow lava sequences. These rocks generally range from sub-alkaline to transitional character. Mineral chemistry and whole-rock geochemistry indicate that they have compositions akin to enriched-type mid-ocean ridge basalts (E-MORB) and plume-type MORB (P-MORB). Nonetheless, the different depletion degrees in heavy rare earth elements (HREE), which can be observed in both E-MORB like and P-MORB like rocks enable two main basic chemical types of rocks to be distinguished as Type-I and Type-II. Type-I rocks are strongly depleted in HREE (YbN 9.0). Petrogenetic modeling shows that Type-I rocks originated from 7 to 16% polybaric partial melting of a MORB-type mantle source, which was significantly enriched by plume-type components. These rocks resulted from the mixing of variable fractions of melts generated in garnet-facies and the spinel-facies mantle. In contrast, Type-II rocks originated from 5 to 8% partial melting in the spinel-facies of a MORB-type source, which was moderately enriched by plume-type components. A possible tectono-magmatic model for the generation of the southern Neo-Tethys oceanic crust implies that the continental rift and subsequent oceanic spreading were associated with uprising of MORB-type asthenospheric mantle featuring plume-type component influences decreasing from deep to shallow mantle levels. These deep plume-type components were most likely inherited from Carboniferous mantle plume activity that was associated with the opening of Paleo-Tethys in the same area.

  20. Petrologic evolution of Miocene-Pliocene mafic volcanism in the Kangal and Gürün basins (Sivas-Malatya), central east Anatolia: Evidence for Miocene anorogenic magmas contaminated by continental crust

    Science.gov (United States)

    Kocaarslan, Ayça; Ersoy, E. Yalçın

    2018-06-01

    This study discusses the geochemical features of the Early-Middle Miocene and Pliocene basaltic (SiO2 = 46-52; MgO = 6-10 wt%) to andesitic (SiO2 = 59; MgO = 4 wt%) rocks exposed in the Gürün and Kangal basins (Sivas, eastern part of central Anatolia), respectively. The basaltic rocks are characterized by alkaline to tholeiitic affinities, while the more evolved andesitic samples show calc-alkaline affinity. Trace element variations reveal that they can be evaluated in three sub-groups, each represented by different contents of trace elements for given Nb contents. Primary magmas of each groups were likely produced by different degrees of partial melting ( 1-2, 2-3, 7-10% respectively) from a common mantle source, subsequently underwent different degrees of fractionation and crustal contamination. Derivation from a common mantle source of the primitive magmas of each group is supported by similar Sr, Nd and Pb isotopic ratios. Increasing degrees of partial melting seem to be responsible for the alkaline to tholeiitic variation among the basaltic samples, while higher degrees of crustal contamination (AFC) resulted in calc-alkaline affinity of the more evolved samples. Most primitive Pliocene samples show intra-plate (anorogenic) geochemical features, while the more evolved Miocene calc-alkaline samples resemble geochemically subduction-related (orogenic) magmatic rocks. However, on the basis of detailed geochemical models, we propose that the calc-alkaline affinity among the Miocene samples can also be gained by crustal contamination of their primary magmas which were also anorogenic in character. If this is true, overall, the Miocene and Pliocene basaltic to andesitic rocks in the Gürün and Kangal basins appear to may have formed by variable degrees of partial melting of a common anorogenic mantle that had not been subject to subduction-related metasomatism. This is an alternative approach to the general view assuming the Early-Middle Miocene magmatic activity in the region was derived from subduction-modified mantle sources in response to subduction of the Arabian Plate under the Anatolian Plate. This hypothesis further implies that either delamination of the sub-continental lithosphere or slab break-off processes beneath the central to eastern Anatolia might took place well before the Miocene, thus allowing upwelling unaltered mantle to provide the source of the Miocene to Pliocene volcanic rocks.

  1. Comparison of hydrothermal alteration patterns associated with porphyry Cu deposits hosted by granitoids and intermediate-mafic volcanic rocks, Kerman Magmatic Arc, Iran: Application of geological, mineralogical and remote sensing data

    Science.gov (United States)

    Yousefi, Seyyed Jabber; Ranjbar, Hojjatollah; Alirezaei, Saeed; Dargahi, Sara; Lentz, David R.

    2018-06-01

    The southern section of the Cenozoic Urumieh-Dokhtar Magmatic Arc (UDMA) of Iran, known as Kerman Magmatic Arc (KMA) or Kerman copper belt, is a major host to porphyry Cu ± Mo ± Au deposits, collectively known as PCDs. In this study, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data and spectral angle mapper (SAM) method, combined with field data, mineralogical studies, and spectral analysis are used to determine hydrothermal alteration patterns related to PCDs in the KMA. Gossans developed over some of these porphyry type deposits were mapped using Landsat 8 data. In the NKMA gossans are more developed than in the SKMA due to comparatively lower rate of erosion. The hydrothermal alteration pattern mapped by ASTER data were evaluated using mineralogical and spectral data. ASTER data proved to be useful for mapping the hydrothermal alteration in this semi-arid type of climate. Also Landsat 8 was useful for mapping the iron oxide minerals in the gossans that are associated with the porphyry copper deposits. Our multidisciplinary approach indicates that unlike the PCDs in the northern KMA that are associated with distinct and widespread propylitic alteration, those in the granitoid country rocks lack propylitic alteration or the alteration is only weakly and irregularly developed. The porphyry systems in southern KMA are further distinguished by development of quartz-rich phyllic alteration zones in the outer parts of the PCDs that could be mapped using remote sensing data. Consideration of variations in alteration patterns and specific alteration assemblages are critical in regional exploration for PCDs.

  2. Fortress Europe

    DEFF Research Database (Denmark)

    Castan Pinos, Jaume

    the enclaves. For instance, this book concentrates on the impact on the enclaves of policies against illegal migration, such as Schengen, and the European Neighbourhood Policy (ENP). These policies together with their geographical isolation and the fences built around their border perimeters with Morocco make...

  3. Threats to wildlife and their utilizable products in the Cross River ...

    African Journals Online (AJOL)

    The study of the threats to wildlife, preference and their utilization was carried out in randomly selected rainforest enclaves of Cross River State. The enclaves are Okwangwo, Wula, Idomi and Oban. Methods used for data collection include use of semi – structured questionnaire, oral interview and field observation.

  4. Composition et évolution du manteau lithosphérique nord-africain : évidences pétrologiques et géochimiques à partir des enclaves de manteau échantillonnées par le volcanisme cénozoïque intraplaque du Moyen Atlas (Maroc)

    OpenAIRE

    Pezzali , Irene

    2013-01-01

    The Ph.D. study is aimed at characterising the composition of pyroxenite xenoliths brought to the surface by Cenozoic intraplate volcanism in the Azrou Timahdite district of Middle Atlas (Morocco) to unravel their origin and significance in the frame of the geodynamic evolution of the North Africa lithospheric mantle. The interpretations are based on a petrological approach and on reliable geochemical information at both bulk rock and mineral scale. The data are used to address a largely deba...

  5. 'Building Fortress Europe? Schengen and the Cases of Ceuta and Melilla'

    DEFF Research Database (Denmark)

    Castan Pinos, Jaume

    Because of their unique geographical location, Ceuta and Melilla are the only places from which Africans can reach European soil without risking their lives in the Mediterranean. As a result, both enclaves are territories in which EU migration policies have a special significance. The fact...... that the ‘gated community’ metaphor, which is the lesser used, is more accurate on the basis that it takes into account cooperation and interaction between both sides of the border. In the case of the enclaves this interaction becomes evident in the selective permeability applied to the enclaves...

  6. The W (Sn-Mo)-specialized catinga suite and other granitoids of the Brusque Group, neo proterozoic of the state of Santa Catarina, Southern Brazil

    International Nuclear Information System (INIS)

    Castro, Neivaldo Araujo de; Crosta, Alvaro Penteado; Basei, Miguel Angelo Stipp

    1999-01-01

    The petrographic, geochemical and isotopic data on the granitoids intrusive in the Brusque Group, State of Santa Catarina, southern Brazil, are presented in this paper. These are late-to post-tectonic rocks, being the most evolved ones those that constitute the Catinga Suite. The granitoids intrusive in the southern domain of the Brusque Group are grayish rocks, in which biotite (when present) is practically the only mafic mineral. They are rather reduced, slightly alkalic, transitional between meta-and peraluminous. An acid subvolcanic pluton, the Ribeirao da Velha pluton, has similar petrographic and geochemical characteristics, and seems to be genetically related to these granitoids. LREE fractionation relative to HREE is incipient for the Catinga suite, and the REE patterns showing strong negative Eu anomaly. Initial 87 Sr/ 86 Sr ratios, from the literature for these granitoids are around 0.721 (Sao Joao Batista granitoid) and the only available t DM model age (Valsungana granitoid) points to a genesis from a continental crust of ca. 2020 Ma old. Gneiss-migmatitic rocks such as those that occur in the eastern portion of Brusque Group domain and as enclaves in the Nova Italia granitoid are strong candidates for protoliths of these granitoids. Little available information on the granitoids intrusive in the northern domain of the Brusque Group reports the presence of pink K-feldspar hornblende granitoids (Faxinal pluton) and light pink K-feldspar biotite granitoid (Guabiruba pluton). These granitoids are more enriched in K and more oxidized than those in the southern domain, and the LREE fractionation relative to HREE is strong, with the REE patterns showing incipient negative Eu anomaly. It is suggested that part of the Au concentrations found in the northern domain may be genetically associated with the granitoids, since they present characteristics favorable to promote Au mineralizations than the granitoids in the southern domain. Distinct protoliths and

  7. Petrogenesis of Luchuba and Wuchaba granitoids in western Qinling: geochronological and geochemical evidence

    Science.gov (United States)

    Kong, Juanjuan; Niu, Yaoling; Duan, Meng; Zhang, Yu; Hu, Yan; Li, Jiyong; Chen, Shuo

    2017-12-01

    . Mafic magmatic enclaves (MMEs) of Wuchaba pluton are earlier cumulates of the same magmatic system. The Mianlue oceanic crust (MORB-like) contributes to the source of the Luchuba and Wuchaba granitoids, pointing to the significance of melting of oceanic crust for continental crust accretion.

  8. Fulltext PDF

    Indian Academy of Sciences (India)

    Jing-Hua Wu

    2017-07-06

    Jul 6, 2017 ... 2001) and (b) regional geological ... as plate subduction and deep mantle processes). Thus, mafic ... ally led to the collision of North China Craton .... tributed mafic dikes with different scales and occur- ... described in Liu et al.

  9. Las rocas catazonales de la región de Cabo Ortegal

    NARCIS (Netherlands)

    Vogel, D.E.

    1967-01-01

    Paragneisses and associated mafic igneous rocks have been subjected twice to regional metamorphism and extensive folding. During the first, catazonal, metamorphism, the mafic rocks have been converted to eclogites and pyrigarnites (hornblende-granulite facies rocks); both characterized by the

  10. Mineralization related to Alvand pluton in the Hamadan, western Iran

    Science.gov (United States)

    Salehi, M. H.; Doosti, E. A.; Ahadnejad, V.

    2009-04-01

    the expanded turmalinization has occurred but it is not seen any mineralization. Unless some small part of Alvand complex (i.e. stibnite in the Faghireh area, Maniijou and Aliani, 2000) and based on the main geochemical index, Alvand granitod pluton is classified as a barren type granite. References: Ghalamghash, J., Mirnejad, H., Rashid, H., Mohammadiha, K., Ghahraei-poor, M., Zakeri, M., 2007. Geochemistry of gabbro, granite and mafic enclaves of Alvand batholithe and their origin. 25th conference of geoscinces, Geological Survey of Iran. Maniijou, M., and Aliani, F., 2000. Stibnite mineralization in the Hamedan, west Iran. Mineral Deposits at the Beginning of the 21st Century: Proceedings of the Joint Sixth Biennial SGA-SEG Meeting, Krakow, Poland, 26-29 August 2001 By Adam Piestrzyński, Society for Geology Applied to Mineral Deposits, Society of Economic Geologists (U.S.) Published by Taylor & Francis. ISBN 9026518463, 9789026518461. 1148 pages. Sepahi, Ali A, 2008. Typology and petrogenesis of granitic rocks in the Sanandaj-Sirjan metamorphic belt, Iran: with emphasis on the Alvand plutonic complex. Neues Jahrbuch für Geologie Und Palaeontologie. Abhandlungen, 2008; 247 (3), 295-312.

  11. Plagioclase Textures and Zoning Patterns in the Miocene Dowdy Ranch Andesite, Central California Coast Ranges: Implications for Open and Closed System Behavior in Magmatic Systems

    Science.gov (United States)

    Bavishi, D. K.; Metzger, E. P.; Miller, J. S.

    2010-12-01

    The Miocene Dowdy Range Andesite (DRA) of the Central California Coast Ranges is part of a northwestward-younging sequence of volcanic rocks that were apparently formed by northward movement of the Mendocino triple junction, formation of a slab window, and infilling by asthenospheric mantle. The highly porphyritic andesite contains plagioclase phenocrysts with a wide array of disequilibrium textures and zoning patterns, providing an opportunity to reconstruct andesite-forming processes in a tectonic environment that evolved from subduction to transform motion. The DRA encloses metasedimentary, granulitic, and gabbroic xenoliths (described elsewhere) and displays arc-like trace element chemistry. It features glomeroporphyritic, intersertal and hyalopilitic textures with plagioclase as the dominant phase both as phenocrysts and in the groundmass. Other groundmass minerals include orthopyroxene, clinopyroxene, and ilmenite. Plagioclase exhibits normal, reverse, oscillatory and patchy zoning patterns and sieve and sponge textures, with several populations of plagioclase crystals observed on the scale of a single thin section. The presence of abundant quartz xenocrysts rimmed by augite and absence of mafic enclaves suggest that incorporation of crustal material played an important role in forming the andesite. Preliminary examination of back-scattered electron images and electron microprobe analysis of zoned plagioclase shows both concordant and discordant relationships between An and FeO, suggesting that the andesite was formed by a combination of open and closed system magmatic processes. Plagioclase cores vary from An 45-65%. Clear rims surrounding spongy zones are common and show abrupt and significant (~10-50% An and 5-20% FeO) increases in both An and FeO, as expected for magma recharge by more mafic magma. Clear rim compositions are consistent from sample to sample, suggesting that the phenocrysts experienced a common history during later stages of

  12. The Impact of Micro-Finance on the Performance of Small-Scale ...

    African Journals Online (AJOL)

    2014-10-02

    Oct 2, 2014 ... Department of Planning and Management ... Keywords: Small-scale Enterprises, Micro-Financing, Micro-Credit, Sales Revenue, .... The Wa Municipality is often acclaimed as a private-sector business enclave in the Upper.

  13. The JMCIS Information Flow Improvement (JIFI) Assurance Strategy

    National Research Council Canada - National Science Library

    Moore, Andrew

    1997-01-01

    The Joint Maritime Command Information System (JMCIS) provides a common operating environment for Naval tactical decision aids that currently operates two distinct system high enclaves, one at SECRET/GENSER and one at TOP SECRET/SCI...

  14. ARTIKULASI IDENTITAS WONG SOLO DI EKS ENKLAVE SURAKARTA: KONSTRUKSI BAHASA DAN PEMERTAHANANNYA

    Directory of Open Access Journals (Sweden)

    Sulistyowati .

    2014-06-01

    Full Text Available Culturally Kotagede and Imogiri consist of the ex enclave regions of Surakarta which are called Kotagede SK and Imogiri SK. The community of the ex Surakarta enclave is also known as Wong Solo. This article describes the existence of Wong Solo in Surakarta ex enclave in maintaining its identities. The label of priyayi, courteous, alus, glamorous, and umuk attached to Wong Solo articulated through language practices and material culture. Historical and sociocultural perspective used to describe the verbal expression as identity markers and narratives elicited through etnographic work. It is assumed that the romanticism of the elite, class consciousness, and awareness of the preservation of tradition dominate retention Wong Solo. Cultural agencies, Surakarta and Yogyakarta Palace in the historical affinity presented by abdi dalem juru kunci of the kings of Mataram cemetery become binding factor of Wong Solo identity in Surakarta ex enclave.

  15. Maheshwari, Prof. Satish Chandra

    Indian Academy of Sciences (India)

    Delhi), FNA, FNASc. Date of birth: 4 October 1933. Specialization: Physiology & Biochemistry of Plant Growth & Development and Plant Molecular Biology Address: 251/56, Prathap Enclave, Haldighati Road, Jaipur 302 033, Rajasthan Contact ...

  16. New Fellows and Honorary Fellow

    Indian Academy of Sciences (India)

    ), FNA, FNASc. Date of birth: 29 October 1914. Date of death: 20 January 2002. Specialization: Medicinal Chemistry Last known address: B-1, Pamposh Enclave, Greater Kailash-1, New Delhi 110 048. YouTube; Twitter; Facebook; Blog ...

  17. Neighborhood context and the Hispanic health paradox: differential effects of immigrant density on children׳s wheezing by poverty, nativity and medical history.

    Science.gov (United States)

    Kim, Young-An; Collins, Timothy W; Grineski, Sara E

    2014-05-01

    Prior research suggests that immigrant enclaves provide respiratory health benefits for US Hispanic residents. We test if immigrant enclaves provide differential respiratory health benefits for Hispanic children in El Paso (Texas) based on individual-level factors. Results reveal that higher neighborhood immigrant density is associated with reduced odds of wheezing, but that the protective immigrant enclave effect is modified by poverty, general health status, body mass index (BMI), and caretaker nativity. Higher immigrant density is significantly more protective for poor children and those with foreign-born caretakers; conversely, it is significantly less protective for children in worse health and those with higher BMI. These findings foster a novel understanding of how immigrant enclaves may be differentially protective for Hispanic children based on individual-level factors. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Smart Push, Smart Pull, Sensor to Shooter in a Multi-Level Secure/Safe (MLS) Infrastructure

    Science.gov (United States)

    2006-05-04

    Communication Periods Processing Resource Sanitization Minimum Interrupt Servicing Semaphores Multi-Core Synchronization Primitives Timers And nothing else...Communities of Interest Secure Configuration of all Nodes in Enclave Bandwidth provisioning & partitioning Secure Clock Synchronization Suppression of

  19. 45 CFR 3.42 - Restricted activities.

    Science.gov (United States)

    2010-10-01

    ... take photographs, films or audiovisuals, for personal or news purposes on the grounds of the enclave or... by appropriate signs. Photographs and similar activities for advertising or commercial purposes may...

  20. MALIKI JURISPRUDENCE AND BOKO HARAM IDEOLOGY ...

    African Journals Online (AJOL)

    Dean SPGS NAU

    in selected enclaves, namely, Indonesia, Pakistan and Malaysia. The ... Hence, the consensus of opinion in Medina regarding any Islamic tradition was seen as a ... materials and in propaganda videos that are regularly released to the public.

  1. A Model of Network Porosity

    Science.gov (United States)

    2016-11-09

    Figure 1. We generally express such networks in terms of the services running in each enclave as well as the routing and firewall rules between the...compromise a server, they can compromise other devices in the same subnet or protected enclave. They probe attached firewalls and routers for open ports and...spam and malware filter would prevent this content from reaching its destination. Content filtering provides another layer of defense to other controls

  2. Using Mobile Platforms for Sensitive Government Business

    Science.gov (United States)

    2013-01-01

    install call, text and data monitoring software within the corporate enclave(s), in order to meter professional usage separately. Personal usage could be...Available from: http://www.3gpp.org/ftp/Specs/archive/33_series/33.908/33908- 400 .zip. 27. Geiger, H. NFC Phones Raise Opportunities, Privacy And...Available from: http://www.pcworld.com/article/212192/protect_your_android_phone_with_sec urity_apps.html. 74. German, K. Sprint offers McAfee

  3. Granitoid magmatism of Alarmaut granite-metamorphic dome, West Chukotka, NE Russia

    Science.gov (United States)

    Luchitskaya, M. V.; Sokolov, S. D.; Bondarenko, G. E.; Katkov, S. M.

    2009-04-01

    ]. Analyses of cores of some zircons from granodiorites of Lupveem batholith indicate Precambrian age of protolith (717, 1070.4 and 1581.5 m.a.) [15]. 40Ar-39Ar age of synmetamorphic biotite varies from 108 to 103 m.a. [15]. Intrusive rocks of Alarmaut dome are represented by wide spectrum of rocks: diorites, Q diorites, Q monzodiorites, granodiorites, tonalites, granites. Granodiorites and granites contain mafic enclaves of monzonites and Q monzonites. SiO2 contents in rocks of Alarmaut dome varies from 58,55% in diorites to 71,3% in granites; in enclaves - from 54,6% in monzonites to 61.89% in Q monzonites. Granitoids are normal and subalkaline rocks according to SiO2 vs K2O+Na2O and belong to high-K calc-alkaline and shoshonite series according to K2O vs SiO2. They are mainly metaluminous rocks (ASI intermediate rocks are characterized by LREE enrichment, HREE depletion and insignificant negative Eu-anomaly (LaN/YbN=8,42-15,69; Eu/Eu*=0,66-0,94). Granodiorites and granites REE patterns are more enriched in LREE, more depleted in HREE and have deeper negative Eu-anomaly (LaN/YbN=11,48-45,6; Eu/Eu*=0,47-0,81). REE patterns of monzonites from enclaves in granites and granodiorites are similar to patterns of host rocks. REE patterns of intermediate rocks and granodiorites are well correlated with those of "mafic root" rocks of K2 Kigluaik pluton from the core part of the same name gneiss dome, Seward Peninsula, Alaska [16], and K1-2 granitoids of Chauna fold zone, West Chukotka [17]. Spidergrams of granitoids and enclaves are similar and characterized by LILE, LREE enrichment and Nb, Sr, P, Ti depletion, typical for supra-subduction magmatites. On F1-F2 diagram [18], separating granitoids by geodynamic settings, granitoids fall in the field of collisional granites; on Rb vs Y+Nb diagram, along the boundary between the fields of syncollisional granites and volcanic arc granites, but within the field of postcollisional [19]. Geochronological and structural data indicate temporal

  4. Evolución metamórfica de los gabros coroníticos de El Arenal, faja máfica-ultramáfica El Destino-Las Águilas, sierra de San Luis Metamorphic evolution of the coronitic gabbrons of the El Arenal, El Destino-Las Aguilas, mafic-ultramafic belt, Sierra de San Luis

    OpenAIRE

    N. Brogioni; G. Cruciani; M. Franceschelli; O. Vaselli

    2007-01-01

    Las meta-melagabronoritas coroníticas se localizan en uno de los cuerpos de El Arenal, pertenecientes a la faja máfica-ultramáfica El Destino-Las Aguilas del flanco oriental de la sierra de San Luis. Son rocas de grano fino y representan fraccionados poco evolucionados, con alto contenido de Cr-Ni y [Mg/Mg+FeT++] comprendidas entre 0,72 y 0,75, derivados de un magma toleítico olivínico de bajo Ti, cuyo emplazamiento precedió a la deformación penetrativa y metamorfismo famatinianos. Las microe...

  5. ANALISIS FAKTOR INTEGRATIF NYAMA BALI-NYAMA SELAM, UNTUK MENYUSUN BUKU PANDUAN KERUKUNAN MASYARAKAT DI ERA OTONOMI DAERAH

    Directory of Open Access Journals (Sweden)

    I Made Pageh

    2014-02-01

    Full Text Available Penelitian ini bertujuan untuk (1 memahami latar belakang sejarah Enclave Nyama Bali–Nyama Selam di Bali; (2 menganalisis faktor integratif Enclave Nyama Bali-Nyama Selam, untuk mengembangkan kerukunan antarumat beragama di Bali; (3 mendapatkan materi penenulisan Model Buku Panduan integrasi sosial pada Enclave Nyama Selam-Nyama Bali di Era Otonomi Daerah. Penelitian ini menggunakan metode penelitian ilmu sosial dengan pendekatan sejarah sosial. Dengan demikian prosedur penelitian ini mengikuti prosedur ilmu sosial (etnografi koneksitas antar situs, dari penentuan informan, pengumpulan data sampai analisis data,  dengan teknik analisis deskriptif kualitatif. Hasil penelitian menunjukkan. latar belakang sejarah kearifan enclave Nyama Bali- Nyama Selam, terutama yang berkaitan dengan menumbuhkembangkan integrasi dan harmoni sosial di era otonomi daerah, tidak dapat dilepaskan dari sejarah masuknya agama Islam ke Bali terkait perdagangan di pinggir pantai, seperti Islam di pinggir pelabuhan Buleleng, Sangsit, Temukus kemudian menyebar ke pedalaman bertani seperti Islam di Pancasari, Tegalinggah, dan Batu Gambir, beberapa islam di pedalaman Karangasem. Enclave Islam  terkait dengan politik kerajaan, tinggal di sekitar kerajaan dan atau di pedalaman membentuk enclave tersendiri (Nyama Selam Pegarayaman, Karangasem, Kepaon, Serangan, Loloan Negara, hubungan nyama selam dengan kerajaan adalah hubungan “patro-klient, tautan kaula gusti. dan migrasi berantai dalam perdagangan sektor informal. Faktor Integratif Enclaves Nyama Bali- Nyama Islam dengan kerajaan, dapat dipahami dari latar belakang sejarah politik kerajaan, dengan menempatkan penduduk muslim mengelilingi puri, sebagai benteng, kasus ini dapat dijumpai pada masa kerajaan Karangasem, Klungkung, Badung, Buleleng dan Jemberana, diikuti dengan perkawinan politik (kasus badung dengan enclave Kepaon. Bentuknya di Bidang Sosial (Perkawinan lintas agama, meminjam identitas etnik magibung, ngejot

  6. Trust Management Considerations For the Cooperative Infrastructure Defense Framework: Trust Relationships, Evidence, and Decisions

    Energy Technology Data Exchange (ETDEWEB)

    Maiden, Wendy M.

    2009-12-01

    Cooperative Infrastructure Defense (CID) is a hierarchical, agent-based, adaptive, cyber-security framework designed to collaboratively protect multiple enclaves or organizations participating in a complex infrastructure. CID employs a swarm of lightweight, mobile agents called Sensors designed to roam hosts throughout a security enclave to find indications of anomalies and report them to host-based Sentinels. The Sensors’ findings become pieces of a larger puzzle, which the Sentinel puts together to determine the problem and respond per policy as given by the enclave-level Sergeant agent. Horizontally across multiple enclaves and vertically within each enclave, authentication and access control technologies are necessary but insufficient authorization mechanisms to ensure that CID agents continue to fulfill their roles in a trustworthy manner. Trust management fills the gap, providing mechanisms to detect malicious agents and offering more robust mechanisms for authorization. This paper identifies the trust relationships throughout the CID hierarchy, the types of trust evidence that could be gathered, and the actions that the CID system could take if an entity is determined to be untrustworthy.

  7. Magma mixing in granitic rocks of the central Sierra Nevada, California

    Science.gov (United States)

    Reid, John B.; Evans, Owen C.; Fates, Dailey G.

    1983-12-01

    The El Capitan alaskite exposed in the North American Wall, Yosemite National Park, was intruded by two sets of mafic dikes that interacted thermally and chemically with the host alaskite. Comparisons of petrographic and compositional data for these dikes and alaskite with published data for Sierra Nevada plutons lead us to suggest that mafic magmas were important in the generation of the Sierra Nevada batholith. Specifically, we conclude that: (1) intrusion of mafic magmas in the lower crust caused partial melting and generation of alaskite (rhyolitic) magmas; (2) interaction between the mafic and felsic magmas lead to the observed linear variation diagrams for major elements; (3) most mafic inclusions in Sierra Nevada plutons represent chilled pillows of mafic magmas, related by fractional crystallization and granitoid assimilation, that dissolve into their felsic host and contaminate it to intermediate (granodioritic) compositions; (4) vesiculation of hydrous mafic magma upon chilling may allow buoyant mafic inclusions and their disaggregation products to collect beneath a pluton's domed ceiling causing the zoning (mafic margins-to-felsic core) that these plutons exhibit.

  8. The diagnosis and management of progressive dysfunction of health care organizations.

    Science.gov (United States)

    Chervenak, Frank A; McCullough, Laurence B

    2005-04-01

    This paper presents an ethically justified approach to the diagnosis and management of progressive dysfunction of health care organizational cultures. We explain the concept of professional integrity in terms of the ethical concept of the cofiduciary responsibility of physicians and health care organizations. We identify the ethical features of a healthy health care organization and the spectrum of progressive dysfunction of organizational cultures from cynical through wonderland and Kafkaesque to postmodern. Physicians should respond to cynical health care organizations by creating moral enclaves of professional integrity for the main purpose of confrontation and reform, to wonderland organizations by strengthening moral enclaves for the main purpose of resisting self-deception, to Kafkaesque organizations by strengthening moral enclaves still further for the main purpose of defending professional integrity (adopting a Machiavellian appearance of virtue as necessary), and to postmodern organizations by creating moral fortresses and, should these fail, quitting.

  9. Postwar Industrial areas as agents for sustainable urban transformation

    DEFF Research Database (Denmark)

    Boye, Anne Mette

    2017-01-01

    Only 30-40 years old, postwar industrial enclaves in Denmark change character. Vacancies, new investments in high technology and new civic programs are recorded even within the same enclaves. These postwar industrial areas represent a generic typology – a legacy of the functionalistic paradigm sh...... international projects, the paper pinpoints a selection of spatial transformation strategies addressing uncertainty. Through this, the paper contributes to the discussion on how to recycle the postwar urban landscape and planning in uncertain conditions....... are cleared for redevelopment or ignored. However, both reactions dismiss the possible qualities of the existing morphology and activities. This paper argues that this might close an opportunity to consider how recycling these enclaves can be utilized to shape future sustainable urban environments...

  10. Three tier transition of Neoarchean TTG-sanukitoid magmatism in the Beit Bridge Complex, Southern Africa

    Science.gov (United States)

    Rajesh, H. M.; Belyanin, G. A.; Van Reenen, D. D.

    2018-01-01

    Neoarchean TTG-sanukitoid associations of contrasting scales occur within the Beit Bridge Complex terrane of the Limpopo Complex in southern Africa. These include the smaller 2.65-2.63 Ga Avoca granitoid and the voluminous 2.73-2.64 Ga Alldays granitoid. This study characterizes the wide compositional spectrum preserved in these two granitoids. The elliptical Avoca pluton consists of a biotite-amphibole-orthopyroxene ± clinopyroxene-bearing core that is dominantly trondhjemite with less dominant tonalite and granodiorite variants, and a thin amphibole-biotite-bearing granite rim, with local occurrence of two-pyroxene-bearing metabasite boudins. While both the core and rim rocks exhibit a linear fabric, the granite in addition preserves a penetrative foliation. Field relations of granite enclaves in the core rocks together with available ages indicate that the core rocks intruded the granite. The foliated biotite ± amphibole-bearing Alldays granitoid contains inclusions of older supracrustals and rocks of the Messina layered intrusion, and is widely distributed. Compositionally, it include tonalites and granodiorites and to a lesser extent trondhjemites. Both the Avoca core and rim rocks are characterized by difference in mineral chemistry, with the mafic minerals Mg-rich in the TTG core, while they are Fe-rich in the granite and metabasite. In comparison, biotite is Mg-rich and amphibole is Fe-rich in the Alldays granitoid. Two groups of Alldays TTG can be delineated in terms of whole-rock geochemical characteristics, and are comparable to the low- to medium-pressure TTG groups delineated by Moyen (2011), while the Avoca TTG is similar to the high-pressure TTG group. The lowest silica samples from each group of granitoid have geochemical characteristics comparable to Archean sanukitoids, with those from the Avoca granitoid similar to low-Ti sanukitoids, and those from the Alldays granitoid similar to low-Ti and high-Ti sanukitoids. Separate petrogenetic models

  11. Cryogenian alkaline magmatism in the Southern Granulite Terrane, India: Petrology, geochemistry, zircon U-Pb ages and Lu-Hf isotopes

    Science.gov (United States)

    Santosh, M.; Yang, Qiong-Yan; Ram Mohan, M.; Tsunogae, T.; Shaji, E.; Satyanarayanan, M.

    2014-11-01

    The Southern Granulite Terrane (SGT) in India preserves the records of the formation and recycling of continental crust from Mesoarchean through Paleoproterozoic to Neoproterozoic and Cambrian, involving multiple subduction-accretion-collision associated with major orogenic cycles. A chain of unmetamorphosed and undeformed alkaline magmatic intrusions occurs along the northern margin of the SGT aligned along paleo-suture zones. Here we investigate two representative plutons from this suite, the Angadimogar syenite (AM) and the Peralimala alkali granite (PM) through field, petrological, geochemical, zircon U-Pb and Lu-Hf studies. Magma mixing and mingling textures and mineral assemblages typical of alkaline rocks are displayed by these plutons. The whole-rock major and trace element data characterize their alkaline nature. In trace element discrimination diagrams, the AM rocks straddle between the VAG (volcanic-arc granites) and WPG (within plate granites) fields with most of the samples confined to the VAG field, whereas the PM rocks are essentially confined to the WPG field. The diversity in some of the geochemical features between the two plutons is interpreted to be the reflection of source heterogeneities. Most zircon grains from the AM and PM plutons display oscillatory zoning typical of magmatic crystallization although some grains, particularly those from the PM pluton, show core-rim structures with dark patchy zoned cores surrounded by irregular thin rims resulting from fluid alteration. The weighted mean 206Pb/238U ages of the magmatic zircons from three samples of the AM syenite are in the range of 781.8 ± 3.8 Ma to 798 ± 3.6 Ma and those from two samples of the PM alkali granite yield ages of 797.5 ± 3.7 Ma and 799 ± 6.2 Ma. A mafic magmatic enclave from the AM pluton shows weighted mean 206Pb/238U age of 795 ± 3.3 Ma. The AM and PM plutons also carry rare xeneocrystic zircons which define upper intercept concordia ages of 3293 ± 13 Ma and 2530

  12. Origin of dioritic magma and its contribution to porphyry Cu-Au mineralization at Pulang in the Yidun arc, eastern Tibet

    Science.gov (United States)

    Cao, Kang; Yang, Zhi-Ming; Xu, Ji-Feng; Fu, Bin; Li, Wei-Kai; Sun, Mao-Yu

    2018-04-01

    The giant Pulang porphyry Cu-Au deposit in the Yidun arc, eastern Tibet, formed due to westward subduction of the Garze-Litang oceanic plate in the Late Triassic. The deposit is hosted in an intrusive complex comprising primarily coarse-grained quartz diorite and cored quartz monzonite. Here, we investigate a suite of simultaneous (216.6 ± 1.9 Ma) diorite porphyries within the complex. The diorite porphyries are geochemically similar to mafic magmatic enclaves (MME) hosted in coarse-grained quartz diorite, and both are characterized by low SiO2 (59.4-63.0 wt%) and high total alkali (Na2O + K2O = 7.0-9.2 wt%), K2O (3.5-6.4 wt%), MgO (3.2-5.5 wt%), and compatible trace element (e.g., Cr = 72-149 ppm) concentrations. They are enriched in large-ion lithophile and light rare earth elements (LILE and LREE, respectively), but depleted in high field-strength and heavy rare earth elements (HFSE and HREE, respectively), and yield variably high (La/Yb)N ratios (17-126, average 65) with weak to negligible Eu anomalies. Furthermore, they yield low (87Sr/86Sr)i ratios (0.7054-0.7067), weakly negative εNd(t) (-2.8 to -0.8) values, and variable zircon εHf(t) (-5.4 to +0.8) and δ18O (6.0‰-6.7‰) values. These geochemical features indicate that the diorite porphyry and MME formed through crustal assimilation of a magma produced during low-degree partial melting of metasomatized phlogopite-rich subcontinental lithospheric mantle. In contrast, the coarse-grained quartz diorite and quartz monzonite have relatively high concentrations of SiO2 (61.1-65.3 wt%), K2O (4.1-5.4 wt%), and total alkali (Na2O + K2O = 7.1-8.1 wt%), and low concentrations of MgO (generally Y ratios (50-63) that indicate an adakitic affinity, and are enriched in LILE, depleted in HFSE, and yield lower (La/Yb)N values (13-20, average 17) than the diorite porphyry and MME. They yield low (87Sr/86Sr)i ratios (0.7046-0.7066), negative εNd(t) (-3.3 to -1.7) values, and zircon εHf(t) and δ18O values of -2.9 to

  13. Zarzalejo granite (Spain). A nomination for 'Global Heritage Stone Resource'

    Science.gov (United States)

    Freire Lista, David Martin; Fort, Rafael; José Varas-Muriel, María

    2015-04-01

    Zarzalejo granite is quarried in the Sierra de Guadarrama (Spanish Central System) foothills, in and around Zarzalejo village, in the province of Madrid, Spain. It is an inequigranular monzogranite medium-to-coarse grained, with a slight porphyritic texture (feldspar phenocrysts) and mafic micro-grained enclaves. In this abstract the candidacy of Zarzalejo granite as a "Global Heritage Resource Stone" (GHSR) is presented. This stone ideally fits the newly proposed designation as it has been used in many heritage buildings and its good petrophysical properties and durability have allowed well preserved constructions such as a Roman road, San Pedro Church in Zarzalejo (1492), Descalzas Reales Monastery in Madrid (1559-1564) and the San Lorenzo del Escorial Royal Monastery (1563-1584), to be declared a World Heritage Site by UNESCO. This level of construction has been a landmark in the extraction and proliferation of historic quarries created due to the high demand that such colossal monuments and buildings with granite, have required for their construction. In the mid-20th century, More, Zarzalejo granite has also been used in restoration works including the Royal Palace and the Reina Sofía Museum (2001-2005), both buildings in Madrid, Spain. Extraction of granite ashlars from tors has been a very frequent activity in the Zarzalejo neighbourhood until mid-twentieth century. So there is also a need to preserve these historic quarries. This type of stone has created a landscape that has been preserved as an open-air museum today where you can see the marks left in the granite due to historic quarry operations. The granite industry has been one of the main pillars of the Zarzalejo regional economy. For centuries, the local community have been engaged in quarrying and have created a cultural landscape based on its building stone. A quarryman monument has been erected in Zarzalejo in honor of this traditional craft as well as an architecture museum at San Lorenzo del

  14. El turismo urbano y la geografía de la ciudad

    Directory of Open Access Journals (Sweden)

    Dennis R. Judd

    2003-08-01

    Full Text Available Para la literatura urbana post-estructuralista, las ciudades aparecen como paisajes fracturados en enclaves protegidos y excluyentes, los cuales colonizan y reemplazan los lugares locales. Consecuentemente, se considera que los enclaves turísticos facilitan el control autoritario del espacio urbano, modificando el consumo y reemplazando y suprimiendo la cultura local con "ambientes Disney". Este artículo plantea que si bien dentro de los enclaves turísticos se intenta -y generalmente se alcanza- un régimen no democrático, directivo y autoritario, incluso en estos espacios el control social no es total; el análisis que aquí se propone respecto de los espacios turísticos revela que la fractura de los espacios de las metrópolis postmodernas puede crear diversidad y diferencia, más que monotonía y uniformidad. Se concluye que, para los visitantes de las ciudades, la distopia urbana predicha por los post-estructuralistas no ha sido aún materializadaFor post-structuralist urban literature, cities appear as landscapes fractured in protected and exclusionary enclaves, which colonize and replace local places. Consequently, it is considered that tourist enclaves facilitate the authoritarian control of urban space, modifying the consumption and replacing and suppressing local culture with Disney-like environments. This article argues that, even when within tourist enclaves a non-democratic, directive and authoritarian regime is attempted -and generally achieved-, in this spaces social control in not complete; the analysis that this article proposes of tourist spaces reveals that the fracture of post-modern metropolises spaces is able to create diversity and difference, more than monotony and uniformity. It is conclude that, for the city visitors, the urban dystopia predicted by post-structuralist scholars has not been materialized yet

  15. Enacting Trust

    OpenAIRE

    Campbell, Brian

    2012-01-01

    Small and removed from the Spanish mainland, the Enclave of Ceuta has always depended\\ud on flows of goods and labour out of the Moroccan hinterland, with individuals from\\ud different ethnic and religious groups forming informal, flexible and personal economic\\ud bonds based on mutual ‘confianza’ (trust). Since its entry into the European Union in 1986,\\ud the Spanish government has erected a border-wall around the enclave, and introduced new\\ud migration policies branding many informal work...

  16. Explanations for Special Neighbourhood Preferences among Ethnic Minorities

    DEFF Research Database (Denmark)

    Andersen, Hans Skifter

    2015-01-01

    In this paper is examined if preferences exist among ethnic minorities for living close to an ethnic social network, in so-called ethnic enclaves, or living in neighbourhoods with many residents belonging to different ethnic minorities. It is analysed to what extent these preferences can be expla......In this paper is examined if preferences exist among ethnic minorities for living close to an ethnic social network, in so-called ethnic enclaves, or living in neighbourhoods with many residents belonging to different ethnic minorities. It is analysed to what extent these preferences can...

  17. Spatial Assimilation in Denmark?

    DEFF Research Database (Denmark)

    Andersen, Hans Skifter

    2010-01-01

    market and discrimination, which limits the housing possibilities for ethnic minorities. Another explanation could be that immigrants for different reasons choose to settle in so-called ethnic enclaves where they can find an ethnic social network, which can support them in their new country....... In traditional research literature about immigration it has been shown that for many immigrants living in enclaves has been a temporary situation. The 'spatial assimilation theory' says that this situation ends when the family has become more integrated in the new society and then moves to other parts...

  18. Depositional model for Rival and Midale subintervals (Mississippian), north-central Burke County, North Dakota

    Energy Technology Data Exchange (ETDEWEB)

    Harris, T.L.

    1988-07-01

    The Rival and Midale subintervals (Charles Formation, Upper Mississippian), north-central Burke County, North Dakota, represent two relative sea level fluctuations. Updip (northeast), the Rival subinterval contains fine to medium-bedded and chicken-wire anhydrite with interbedded algal bindstone that was deposited on supratidal flats. Basinward (southwest), the lithology changes to oncolitic, peloidal, intraclastic grainstone/packstone that was deposited in intertidal and subtidal restricted lagoonal environments. Evaporites precipitated in the sediment of the intertidal to shallow subtidal restricted lagoonal environment. Overlying the Rival subinterval is skeletal wackestone and packstone of the lower Midale subinterval. The presence of normal-marine fauna (crinoids, brachiopods, trilobites, rugose and tabulate coral) indicates a significant relative sea level transgression occurred following deposition of the Rival. The middle and upper Midale subinterval consists of intensely burrowed dolowackestone and dolomudstone that contain a less diversified faunal assemblage. Overlying the Midale carbonates is a transitional zone of calcareous shale and dolomite that grades upward into mottled (burrowed.) and finely laminated microgranular dolomite and anhydrite. The upper Midale section represents a relative sea level regression (shoreline progradation). Updip (northeast) reservoirs produce from the Midale carbonates, which are sealed laterally and vertically by calcarous shale and microgranular dolomitic anhydrite of the Midale Evaporite. Downdip (southwest), the Rival produces from porous grainstone, which is sealed laterally by intertidal/supratidal carbonates and evaporites, resulting in a stratigraphic trap. Vuggy and intergranular porosity are the major porosity types in the Rival grainstone, and moldic and intercrystalline porosity are dominant in the Midale dolowackestone.

  19. Vesuvianite–wollastonite–grossular-bearing calc-silicate rock near ...

    Indian Academy of Sciences (India)

    Felsic layers are white in colour, whereas mafic layers range from green, brown to grey colour depending on the modal abundance of different mafic minerals. Layers rich in diopside are green coloured and those rich in garnet are brown. Keywords. Vesuvianite; wollastonite; grossular; diopside; calc-silicate rock. J. Earth ...

  20. Shear wave velocity structure of the Bushveld Complex, South Africa

    CSIR Research Space (South Africa)

    Kgaswane, EM

    2012-07-01

    Full Text Available crustal layers may be as high as 3.7–3.8 km/s, consistent with the presence of mafic lithologies. These results favor a continuous-sheet model for the Bushveld Complex in which the outcropping mafic layers of the western and eastern limbs are continuous...

  1. No Moho uplift below the Baikal Rift Zone

    DEFF Research Database (Denmark)

    Nielsen, Christoffer; Thybo, Hans

    2009-01-01

    .4-7.6 ± 0.2 km/s), slightly offset to the northeast from the rift axis. We interpret this feature as resulting from mafic intrusions. Their presence may explain the flat Moho by compensation of lower crustal thinning by intrusion of mafic melts. The Pn wave velocities (8.15-8.2 km/s) are normal for the area...

  2. Soil diversity and hydration as observed by ChemCam at Gale Crater, Mars

    NARCIS (Netherlands)

    Meslin, P.-Y.; Gasnault, O.; Forni, O.; Schröder, S.; Cousin, A.; Berger, G.; Clegg, S.M.; Lasue, J.; Maurice, S.; Sautter, V.; Le Mouélic, S.; Wiens, R.C.; Fabre, C.; Goetz, W.; Bish, D.; Mangold, N.; Ehlmann, B.; Lanza, N.; Harri, A.-M.; Anderson, R.; Rampe, E.; McConnochie, T.H.; Pinet, P.; Blaney, D.; Léveillé, R.; Archer, D.; Barraclough, B.; Bender, S.; Blake, D.; Blank, J.G.; Bridges, N.; Clark, B.C.; DeFlores, L.; Delapp, D.; Dromart, G.; Dyar, M.D.; Fisk, M.; Gondet, B.; Grotzinger, J.; Herkenhoff, K.; Johnson, J.; Lacour, J.-L.; Langevin, Y.; Leshin, L.; Lewin, E.; Madsen, M.B.; Melikechi, N.; Mezzacappa, A.; Mischna, M.A.; Moores, J.E.; Newsom, H.; Ollila, A.; Perez, R.; Renno, N.; Sirven, J.-B.; Tokar, R.; De La Torre, M.; D'Uston, L.; Vaniman, D.; Yingst, A.; MSL Science Team, the

    2013-01-01

    The ChemCam instrument, which provides insight into martian soil chemistry at the submillimeter scale, identified two principal soil types along the Curiosity rover traverse: a fine-grained mafic type and a locally derived, coarse-grained felsic type. The mafic soil component is representative of

  3. Behaviour of the Sm-Nd and Rb-Sr systems of the mafic-ultramafic layered sequence from Ribeirao dos Motas (Archaean), meridional craton Sao Francisco: evidences of mantle source enrichment and isotopic fractionation; Comportamento dos sistemas Sm-Nd e Rb-Sr da sequencia acamadada mafico-ultramafico Ribeirao dos Motas (Arqueano), craton Sao Francisco Meridional: evidencias de enriquecimento mantelico e fracionamento isotopico

    Energy Technology Data Exchange (ETDEWEB)

    Carneiro, Mauricio Antonio; Carvalho Junior, Irneu Mendes de; Oliveira, Arildo Henrique de [Ouro Preto Univ., (UFOP), MG (Brazil). Dept. de Geologia]. E-mail: mauricio@degeo.ufop.br; Teixeira, Wilson [Sao Paulo Univ., SP (Brazil). Inst. de Geociencias. Dept. de Mineralogia e Geotectonica; Pimentel, Marcio Martins [Brasilia Univ., DF (Brazil). Inst. de Geociencias. Lab. de Geocronologia

    2004-10-15

    The Ribeirao dos Motas layered sequence (SARM) crops out in the southern part of the Sao Francisco Craton, Brazil. This sequence comprises phaneritic meta ultramafic and metamafic rocks, which, although slightly deformed and metamorphosed, retain primary igneous layers. Porphyritic rocks with idiomorphic pyroxene crystals and heteradcumulate and adcumulate textures are also present. Eighteen isotopic analyses were performed in the SARM, comprising rocks with primary (relict) textures, as well as rocks in amphibolite facies and retro-metamorphosed to green-schist facies. Seven samples yield a Sm/Nd isochron age of 2.79 +- 0.30 Ga (MSWD=1.2 e epsilon {sub Ndt}=+0.48), constraining the accretion time of the SARM rocks. The positive epsilon {sub Ndt} value coupled with the Rb/Sr evidence is consistent with mantle source relatively enriched in Nd and Sr isotopes. Nevertheless, some SARM samples display isotopic fractionation and disturbance, which can be ascribed to the following processes or their combinations: a) mobilization of the incompatible elements due to regional high grade metamorphism; b) isotopic changes during upper amphibolite facies overprint; c) isotopic resetting by low-grade fluids associated to the Claudio Shear zone, which is located nearby the SARM. (author)

  4. Markov Chain Monte Carlo Methods

    Indian Academy of Sciences (India)

    Author Affiliations. K B Athreya1 Mohan Delampady2 T Krishnan3. School of ORIE Rhodes Hall Cornell University, Ithaca New York 14853, USA; Indian Statistical Institute 8th Mile, Mysore Road Bangalore 560059, India. Systat Software Asia-Pacific Ltd. Floor 5, 'C' Tower Golden Enclave, Airport Road Bangalore 560 017, ...

  5. 122 DEMYSTIFICATION OF MYTHIC MONSTERS AND THE ...

    African Journals Online (AJOL)

    Tracie1

    are known in oral tradition or written record in too ... pattern of narration or performance” (Okpewho 3). ... dynamic rendering of historical alternatives to give .... In a ritual contest enacted with charms music .... live and rule society from such evil enclaves. The .... different conception of the relationship Лetween drama.

  6. Browse Title Index

    African Journals Online (AJOL)

    ... the management of congestive heart failure in sub-Saharan Africa: experience of the ... aigue du poumon en rapport avec un myxome enclavé dans la valve mitrale ... carcinoma complicating a repetitive injury by the dental prosthesis: a case ...

  7. Classical and quantum mechanics of complex Hamiltonian systems ...

    Indian Academy of Sciences (India)

    Vol. 73, No. 2. — journal of. August 2009 physics pp. 287–297. Classical and quantum mechanics of complex. Hamiltonian systems: An extended complex phase space ... 1Department of Physics, Ramjas College (University Enclave), University of Delhi,. Delhi 110 ... 1.1 Motivation behind the study of complex Hamiltonians.

  8. 45 CFR 3.23 - Parking.

    Science.gov (United States)

    2010-10-01

    ... DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL ADMINISTRATION CONDUCT OF PERSONS AND TRAFFIC ON THE NATIONAL INSTITUTES OF HEALTH FEDERAL ENCLAVE Traffic Regulations § 3.23 Parking. (a) A person may not stand (vehicle... sign, crosswalk, or traffic control signal; (5) In a double-parked position; (6) At a curb painted...

  9. Reconstructing modalities of magma storage in the crust by thermo-rheological modelling

    Science.gov (United States)

    Caricchi, L.; Annen, C.; Rust, A.; Blundy, J.

    2012-04-01

    During my PhD I worked under the supervision of Luigi Burlini studying the rheological behaviour of magma. Luigi was not only a great teacher and friend but he was also able to project the science he was performing beyond the obvious applications. This aspect of Luigi's approach shaped my approach to research and brought me to think to ways of applying the studies we performed together to unravel the complexity of nature that impassioned and inspired him. This contribution comes from the motivation and interest that Luigi created in me during the short, but truly memorable journey we shared together. This study combines petrology, thermal modelling and magma rheology to characterise timescales and modalities of magma emplacement in the Earth's crust. Thermal modelling was performed to determine the influence of magma injection rates in the crust on the temperature evolution of a magmatic body. The injected tonalitic magma was considered to contain dioritic enclaves, common in plutons. The contrast in chemical composition between host and enclaves leads to different crystallinities of these magmas during cooling and produce a rheological contrast that permits reciprocal deformation only in restricted temperature ranges. Characterising the thermal and rheological evolution of host magma and enclaves, we traced the evolution of strain recorded by these inclusions during the construction of an intrusion, showing that the strain recorded by enclaves distributed in different portions of a pluton can be used to constrain thermal evolution in time, magmatic fluxes and timescale of assemblage of magmatic bodies in the crust.

  10. Arora, Dr Baldev Raj

    Indian Academy of Sciences (India)

    Date of birth: 10 October 1947. Specialization: Electromagnetic Geophysics, Seismotectonics and Geomagnetism Address: 36, Janakpuri, Engineers Enclave, Phase III, GMS Road, Dehra Dun 248 001, Uttarakhand Contact: Residence: 98712 87209. Mobile: 98973 91661. Email: arorabr47@gmail.com. YouTube; Twitter ...

  11. New Fellows and Honorary Fellow

    Indian Academy of Sciences (India)

    Elected: 1975 Section: Physics. Venkataraman, Prof. Balu Ph.D. (Columbia). Date of birth: 17 December 1929. Date of death: 28 October 2010. Specialization: Chemical Physics Last known address: A-4/1, Century Enclave, 54(Old), 8(New), Kalakshetra Road, Thiruvanmiyur, Chennai 600 041. YouTube; Twitter; Facebook ...

  12. The political economy of local content in African extractives

    DEFF Research Database (Denmark)

    Buur, Lars; Hansen, Michael; Kjær, Mette

    Extractive foreign direct investment (FDI) is heralded as the new development opportunity in Africa. But extractive FDI has a record of producing enclaves in host countries with few linkages to the local economy. Only if it creates local content will extractive FDI become a catalyst of development...

  13. New Fellows and Honorary Fellow

    Indian Academy of Sciences (India)

    Date of birth: 15 February 1904. Date of death: 23 February 1991. Specialization: Insect Parasitism, Biological Control of Insect Pests & Noxious Weeds, Apiculture, Sericulture and General Entomology Last known address: Sri Girija Shankar Nivas, B-122, Sravodaya Enclave, Sri Aurobindo Marg, New Delhi 110 017.

  14. Decontrolled by solidarity: understanding recreational violence in moral holidays

    NARCIS (Netherlands)

    Weenink, D.

    2013-01-01

    This paper seeks to develop an understanding of ‘recreational’ youth violence against strangers in ‘moral holidays’. These are enclaves in which youth seek to enjoy disorder and disruption. Drawing on Eliasian theory and Collins’s micro-sociology of violence, it is argued that violent moral holidays

  15. Thuiswedstrijd in een vreemd land : Een sociaal wetenschappelijke analyse van voetbal in eigen kring

    NARCIS (Netherlands)

    Ramsahai, S.

    2008-01-01

    The object of this study is to examine the processes that have lead to the establishment and significance of soccer clubs of immigrants in The Netherlands. Further, a comparison has been made between the immigrant soccer players who are involved in ethnic enclave sport and immigrant soccer players

  16. Culturally Responsive Contexts: Establishing Relationships for Inclusion

    Science.gov (United States)

    Berryman, Mere; Ford, Therese; Nevin, Ann; SooHoo, Suzanne

    2015-01-01

    As our education systems become more culturally, ethnically and linguistically diverse, rather than benefiting and learning from each other, we still expect all students to be represented within the same curriculum, pedagogy and testing regimen or we form separate enclaves resulting in marginalizaton. When diverse students have physical and/or…

  17. Author Details

    African Journals Online (AJOL)

    Kola-Oladiji, KI. Vol 9, No 2 (2011) - Articles Effect of Pre-Treatments on the Germination Capacity and Early Growth of Dacryodes Edulis at Nursery Stage Abstract · Vol 12, No 2 (2014) - Articles Gender analysis of non-timber forest products (NTFPs) collection, processing and marreting in rural enclaves of Omo biosphere, ...

  18. Untitled

    Indian Academy of Sciences (India)

    Geological Survey of India, 27, Jawaharlal Nehru Road, Calcutta, 700016 ... In the eastern belt these occur as a long, linear enclave within the ... One of the groups shows a tholeiitic trend and include samples mostly from the eastern belt while ...

  19. NATO Education and Training Network

    Science.gov (United States)

    2012-02-01

    Federated Battle Laboratories Network (CFBLNet) .............................................. 15  5.1  History ...CFBLNet countries, NATO nations and Partners perspective (January 2009) 5.1 History In April 1999, the US made a proposal to the NATO C3 Board to...permanent subscription provides standard access to the: • CFBLNet Blackbone ( IPv4 (IPv6) transport network) • CFBLNet CUE (Unclassified Enclave all

  20. 75 FR 9548 - Reduction of Use of Social Security Numbers (SSN) in the Department of Defense (DoD)

    Science.gov (United States)

    2010-03-03

    ... privileges. Examples include office automation, electronic mail, Web services, and major functional or... enclave responsible for connecting computing environments by providing short-haul data transport capabilities such as local or campus area networks, or long- haul data transport capabilities such as...

  1. 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,.

  2. New Fellows and Honorary Fellow

    Indian Academy of Sciences (India)

    ... FNA, FTWAS Council Service: 1968-85; Vice-President: 1971-73; President: 1974-76. Date of birth: 28 August 1928. Date of death: 22 November 2016. Specialization: Cosmic Rays, Particle Physics Last known address: C-178, First Floor, Sarvodaya Enclave, New Delhi 110 017, U.T.. YouTube; Twitter; Facebook; Blog ...

  3. Culturally Responsive Peace Education: A Case Study at One Urban Latino K-8 Catholic School

    Science.gov (United States)

    Buck, Brandon

    2016-01-01

    This paper presents a case study of a yearlong research-based peace education program at one urban K-8 private Catholic school situated in a community plagued by structural violence in an enclave of a large Midwestern city. To frame the analysis, the author employs concepts central to culturally responsive pedagogy (including cultural competence,…

  4. Mothers' Parenting Dimensions and Adolescent Externalizing and Internalizing Behaviors in a Low-Income, Urban Mexican American Sample

    Science.gov (United States)

    Manongdo, Jennifer A.; Garcia, Jorge I. Ramirez

    2007-01-01

    The relation between adolescent-reported parenting behaviors and mother-reported youth externalizing and internalizing behaviors was examined among 91 Mexican American mother-adolescent (ages 13-17) dyads recruited from an immigrant enclave in a large midwestern metropolitan area. Two major dimensions of mothers' parenting emerged: supportive…

  5. New Fellows and Honorary Fellow

    Indian Academy of Sciences (India)

    Kanungo, Prof. Madhu Sudan Ph.D. (Illinois), FNA, FNASc, FAMS. Date of birth: 1 April 1927. Date of death: 26 July 2011. Specialization: Biochemistry & Molecular Biology of Development & Ageing and Neuroscience Last known address: 9GF, Old Medical Enclave, Banaras Hindu University Campus, Varanasi 221 005.

  6. Tandon, Prof. Prakash Narain

    Indian Academy of Sciences (India)

    Home; Fellowship. Fellow Profile. Elected: 1983 Section: Medicine. Tandon, Prof. Prakash Narain M.B.B.S. (Lucknow), M.S., D.Sc. (h.c.), FRCS, FNA, FNASc, FTWAS, FAMS. Date of birth: 13 August 1928. Specialization: Neurosciences and Neurosurgery Address: No. 1, Jagriti Enclave, Vikas Marg Extension, Delhi 110 092, ...

  7. Gas Flaring, Environmental Pollution and Abatement Measures in ...

    African Journals Online (AJOL)

    The environmental impact of gas flaring on the oil bearing enclave of the Niger Delta, Nigeria, was examined with a view to evaluating the abatement measures put in place by the Federal government of Nigeria and the oil producing companies. Primary and secondary information and data were analyzed during the study.

  8. Epidemiology of Snake Bites among Selected Communities in the ...

    African Journals Online (AJOL)

    Snake is one of the major group of games feared by people in many localities because of their venoms, yet snakes are equally afraid of human beings. This balance of terror apart from affecting both man and snakes has also led to their deaths. Epidemiology of snake bites among selected communities in the enclave of ...

  9. AFRICAN MIGRANTS IN SPITE OF “FORTRESS” EUROPE: AN ...

    African Journals Online (AJOL)

    user

    asylum seekers, and the so-called 'economic migrants.' It is surprising, however ... Spanish enclaves, etc., this paper seeks to underline the major thesis that Africa-to-Europe .... This is the horrible aspect of the African condition. Of his aspect ...

  10. Markov Chain Monte Carlo Methods

    Indian Academy of Sciences (India)

    K B Athreya1 Mohan Delampady2 T Krishnan3. School of ORIE Rhodes Hall Cornell University, Ithaca New York 14853, USA. Indian Statistical Institute 8th Mile, Mysore Rood Bangalore 560 059, India. Systat Software Asia-Pacific Ltd. Floor 5, 'C' Tower Golden Enclave, Airport Rood Bangalore 560 017, India.

  11. Primera cita y confirmación de reproducción de Gomphus vulgatissimus (Linnaeus, 1758 (Odonata: Gomphidae en Gipuzkoa (País Vasco, España.

    Directory of Open Access Journals (Sweden)

    Leire Paz

    2017-01-01

    Full Text Available Con la detección en 2016 de una larva de Gomphus vulgatisimus (Linnaeus, 1758 en el río Araxes se cita la especie por primera vez en el Territorio Histórico de Gipuzkoa (N Península Ibérica, confirmándose asimismo su reproducción en este enclave.

  12. El peñón de Salobreña. Pasado, presente y posibilidades de futuro

    OpenAIRE

    Sánchez Holgado, José Ramón

    2017-01-01

    Entre sus diversos usos a lo largo de los siglos, el peñón de Salobreña se utilizó desde cuando era un islote como un enclave geoestratégico fundamental para una posición avanzada de tropas, en el control diario de la navegación marítima costera

  13. The Effect of Trade Liberalization on Export-Oriented Output and FDI ...

    African Journals Online (AJOL)

    The export-processing zone in Mauritius has existed side-by-side with a highly protected importcompeting sector. The enclave status of an EPZ is supposed, in theory, to insulate the zone against the extra-zone protectionist regime. In that case, will trade liberalization affect EPZ activity? This is the question that the paper ...

  14. 1628-IJBCS-Article-Dan Guimbo

    African Journals Online (AJOL)

    hp

    diminuer le risque de dégradation de l'environnement immédiat du parc W du Niger. © 2012 International ... question de la gestion rationnelle des espèces végétales est de ..... zones enclavées, les véhicules de transports ne sont disponibles ...

  15. Trilingual Code-Switching Using Quantitative Lenses: An Exploratory Study on Hokaglish

    Science.gov (United States)

    Gonzales, Wilkinson Daniel Wong

    2016-01-01

    Adopting a quantitative approach, this paper highlights findings of an exploratory study on Hokaglish, initially describing it as a trilingual code-switching phenomenon involving Hokkien, Tagalog, and English in a Filipino-Chinese enclave in Binondo, Manila, the Philippines. Departing from the (socio)linguistic landscape of the archipelagic…

  16. Women Pursuing Higher Education in Ultra-Orthodox Society

    Science.gov (United States)

    Baum, Nehami; Yedidya, Tova; Schwartz, Chaya; Aran, Ofra

    2014-01-01

    The study reported in this article concerns the beginnings of higher education for women in the Haredi (ultra-Orthodox) enclave in Israel. Haredi Jews are a self-secluded fundamentalist group committed to particularly strict interpretation of Jewish religious law. In recent years, they have been compelled by poverty and other factors to allow…

  17. Assessment of the distribution and conservation status of the viviparous toad Nimbaphrynoides occidentalis on Monts Nimba, Guinea

    NARCIS (Netherlands)

    Hillers, A.; Loua, N.-S.; Rödel, M.-O.

    2008-01-01

    We investigated the distribution of the viviparous Nimba toad Nimbaphrynoides occidentalis throughout its potential range, the montane grasslands of the Monts Nimba massif, West Africa. Although predominantly part of a World Heritage Site, the Monts Nimba also comprise a mining enclave in the

  18. Petrology, geochronology, geochemistry and petrogenesis of Bajestan granitoids, North of Ferdows, Khorasan Razvi Province

    Directory of Open Access Journals (Sweden)

    Reyhaneh Ahmadirouhani

    2017-02-01

    isotopic compositions were also determined for the same samples (i.e. U-Pb samples using the whole-rock method. The samples were analyzed in the Laboratório de Geologia Isotópica da Universidade de Aveiro, Portugal. Results Granitoids in the study area have mostly monzogranite (biotite monzogranite, hornblende biotite monzogranite and pyroxene hornblende biotite monzogranite, granite, and syenogranite composition. Granular, micro-granular, and porphyritic textures are common textures in these rocks. Common mafic minerals in these rocks include biotite, hornblende and pyroxene. Based on mineralogy, low values of magnetic susceptibility, high aluminum saturation index, and high initial 87Sr/86Sr ratios (> 0.710 of the study of granitoid rocks belong to the ilmenite-series of the reduced S-type granitoids. These magmas originated from the upper continental crust at a syncollosion zone. Furthermore, the rocks normalizing spider diagrams showed characteristics of a crustal environment. The age of the granitoids based on zircon U–Pb age dating was determined, including granite porphyry (79±1 Ma, syenogranite (76±1 Ma, biotite monzogranite (76±1 Ma, all of which belong to the Upper Cretaceous (Campanian, except pyroxene hornblende biotite monzogranite with 30.7±1 Ma, Oligocene age (Rupelian has a different age. The ranges of their initial 87Sr/86Sr and 143Nd/144Nd ratios for Upper Cretaceous granitoids are 0.710897–0.717908 and 0.511995–0.512186, respectively while they are 0.713292 and 0.512186 for Oligocene intrusion. The initial єNd isotope values for the syenogranite, biotite monzogranite, and granite porphyry are -10.65, -7.38 and -9.51, respectively. The initial єNd isotope value for pyroxene hornblende biotite monzogranite is -8.06. The values of the igneous rocks could be considered as representative of continental crust derived from magma, and melt derived from psammite rocks is considered to have been the source of the granitoids. Discussion Based on the U

  19. Isotopic evidence for multiple contributions to felsic magma chambers

    DEFF Research Database (Denmark)

    Waight, Tod Earle; Wiebe, R.A.; Krogstad, E.J.

    2007-01-01

    The Gouldsboro Granite forms part of the Coastal Maine Magmatic Province, a region characterized by granitic plutons that are intimately linked temporally and petrogenetically with abundant co-existing mafic magmas. The pluton is complex and preserves a felsic magma chamber underlain...... with identical isotopic compositions to more mafic dikes suggest that closed system fractionation may be occurring in deeper level chambers prior to injection to shallower levels. The granitic portion of the pluton has the highest Nd isotopic composition (eNd=+3.0) of plutons in the region whereas the mafic...

  20. Physico-Chemical conditions of four calc-alkaline granitoid plutons ...

    Indian Academy of Sciences (India)

    63

    Centre), Indian Institute of Technology, Roorkee. An accelerating .... microcline which pinch out into more mafic matrix several millimeters from both ends of ..... In low oxygen fugacity, on the contrary, the introduction of Fe2+ is favoured in.

  1. Water - rock interaction in different rock environments

    International Nuclear Information System (INIS)

    Lamminen, S.

    1995-01-01

    The study assesses the groundwater geochemistry and geological environment of 44 study sites for radioactive waste disposal. Initially, the study sites were divided by rock type into 5 groups: (1) acid - intermediate rocks, (2) mafic - ultramafic rocks, (3) gabbros, amphibolites and gneisses that contain calc-silicate (skarn) rocks, (4) carbonates and (5) sandstones. Separate assessments are made of acid - intermediate plutonic rocks and of a subgroup that comprises migmatites, granite and mica gneiss. These all belong to the group of acid - intermediate rocks. Within the mafic -ultramafic rock group, a subgroup that comprises mafic - ultramafic plutonic rocks, serpentinites, mafic - ultramafic volcanic rocks and volcanic - sedimentary schists is also evaluated separately. Bedrock groundwaters are classified by their concentration of total dissolved solids as fresh, brackish, saline, strongly saline and brine-class groundwaters. (75 refs., 24 figs., 3 tabs.)

  2. Interaction between felsic granitoids and basic dykes in ...

    Indian Academy of Sciences (India)

    37

    Many workers gave detailed petrographical and geochemical data of the ... greenstone complex (Malviya et al., 2006; Kumar et al., 2013; Singh and ...... Mafic rock shows lobate shape pointing towards granitoids (marked by the white arrows);.

  3. Determination of some main elements and traces by x-ray fluorescence analysis in silicate rocks: a comparative study of two analytical techniques

    International Nuclear Information System (INIS)

    Andrade, M.D. de.

    1977-01-01

    The determinations of silicon, magnesium, iron, potassium, calcium, titanium, manganese, barium, strontium, rubidium, zirconium and scandium in felsic and mafic rocks, by X ray fluorescence analysis are presented. (author)

  4. Hydrothermal Gold Mineralization and Structural Controls near May ...

    African Journals Online (AJOL)

    Mickiale

    Structural data suggests four phases of deformations and NE-SW trending foliation is ... Hawzein area and reported presence of hydrothermal gold and base metal ..... coarse mafic and plagioclase minerals in fine grained ground mass matrix ...

  5. SUBJECT INDEX

    Indian Academy of Sciences (India)

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

    alkaline mafic dykes from Swangkre-Rongmil,. East Garo Hills, Shillong plateau, northeast. India. 683. Basalts. Chemical evolution, petrogenesis, and regional chem- ical correlations of the flood basalt sequence in the central Deccan Traps, India.

  6. Linking Orbital, Field, and Laboratory Analyses of Dolerites in the McMurdo Dry Valleys of Antarctica: Terrestrial Studies and Planetary Applications

    Science.gov (United States)

    Salvatore, M. R.; Mustard, J. F.; Head, J. W.; Marchant, D. R.; Wyatt, M. B.; Seeley, J.

    2012-03-01

    Primary igneous and secondary alteration signatures can be resolved using orbital spectroscopy over mafic regions of the McMurdo Dry Valleys. We assess the nature of these signatures and their link to surface stability and regional microclimates.

  7. Relative chronology in high-grade crystalline terrain of the Eastern Ghats, India: new insights

    Science.gov (United States)

    Bhattacharya, S.; Kar, R.; Saw, A. K.; Das, P.

    2011-01-01

    The two major lithology or gneiss components in the polycyclic granulite terrain of the Eastern Ghats, India, are the supracrustal rocks, commonly described as khondalites, and the charnockite-gneiss. Many of the workers considered the khondalites as the oldest component with unknown basement and the charnockite-protoliths as intrusive into the khondalites. However, geochronological data do not corroborate the aforesaid relations. The field relations of the hornblende- mafic granulite with the two gneiss components together with geocronological data indicate that khondalite sediments were deposited on older mafic crustal rocks. We propose a different scenario: Mafic basement and supracrustal rocks were subsequently deformed and metamorphosed together at high to ultra-high temperatures - partial melting of mafic rocks producing the charnockitic melt; and partial melting of pelitic sediments producing the peraluminous granitoids. This is compatible with all the geochronological data as well as the petrogenetic model of partial melting for the charnockitic rocks in the Eastern Ghats Belt.

  8. Lithology, monsoon and sea-surface current control on provenance, dispersal and deposition of sediments over the Andaman continental shelf

    Digital Repository Service at National Institute of Oceanography (India)

    Damodararao, K.; Singh, S.K.; Rai, V.K.; Ramaswamy, V.; Rao, P.S.

    , constrain their transport pathways and assess the factors influencing the erosion in the catchment and their dispersal and deposition over the Andaman Shelf region. Major elemental compositions of the shelf sediments suggest mafic lithology...

  9. Mahoma - Guaycuru project. Mining study possibilities around Mahoma - Guaycuru

    International Nuclear Information System (INIS)

    Coronel, N.; Techera, J.

    1991-01-01

    This work is about the mining study possibilities in Mahoma - Guaycuru mafic complex and the stratified ultramafic complex in the black hill area - San Jose and Colon ia town. These zones have good mining chances because of the geological environment

  10. CONNECTION OF THE NEO-TETHYAN OCEAN TO THE RISE OF ...

    Indian Academy of Sciences (India)

    Table of contents. CONNECTION OF THE NEO-TETHYAN OCEAN TO THE RISE OF THE HIMALAYAN MOUNTAIN BELT · Slide 2 · Slide 3 · Slide 4 · Slide 5 · Slide 6 · Slide 7 · Slide 8 · Slide 9 · Slide 10 · Slide 11 · LADAKH MAFIC MAGMATIC ROCKS (INDUS SUTURE ZONE) · Contrast in characteristics for the mafic ...

  11. Intrusion of basaltic magma into a crystallizing granitic magma chamber: The Cordillera del Paine pluton in southern Chile

    Science.gov (United States)

    Michael, Peter J.

    1991-10-01

    The Cordillera del Paine pluton in the southernmost Andes of Chile represents a deeply dissected magma chamber where mafic magma intruded into crystallizing granitic magma. Throughout much of the 10x15 km pluton, there is a sharp and continuous boundary at a remarkably constant elevation of 1,100 m that separates granitic rocks (Cordillera del Paine or CP granite: 69 77% SiO2) which make up the upper levels of the pluton from mafic and comingled rocks (Paine Mafic Complex or PMC: 45 60% SiO2) which dominate the lower exposures of the pluton. Chilled, crenulate, disrupted contacts of mafic rock against granite demonstrate that partly crystallized granite was intruded by mafic magma which solidified prior to complete crystallization of the granitic magma. The boundary at 1,100 m was a large and stable density contrast between the denser, hotter mafic magma and cooler granitic magma. The granitic magma was more solidified near the margins of the chamber when mafic intrusion occurred, and the PMC is less disrupted by granites there. Near the pluton margins, the PMC grades upward irregularly from cumulate gabbros to monzodiorites. Mafic magma differentiated largely by fractional crystallization as indicated by the presence of cumulate rocks and by the low levels of compatible elements in most PMC rocks. The compositional gap between the PMC and CP granite indicates that mixing (blending) of granitic magma into the mafic magma was less important, although it is apparent from mineral assemblages in mafic rocks. Granitic magma may have incorporated small amounts of mafic liquid that had evolved to >60% SiO2 by crystallization. Mixing was inhibited by the extent of crystallization of the granite, and by the thermal contrast and the stable density contrast between the magmas. PMC gabbros display disequilibrium mineral assemblages including early formed zoned olivine (with orthopyroxene coronas), clinopyroxene, calcic plagioclase and paragasite and later-formed amphibole

  12. Towards Reducing the Data Exfiltration Surface for the Insider Threat

    Energy Technology Data Exchange (ETDEWEB)

    Schlicher, Bob G [ORNL; MacIntyre, Lawrence Paul [ORNL; Abercrombie, Robert K [ORNL

    2016-01-01

    Unauthorized data exfiltrations from both insiders and outsiders are costly and damaging. Network communication resources can be used for transporting data illicitly out of the enterprise or cloud. Combined with built-in malware copying utilities, we define this as comprising the Data Exfiltration Surface (DXS). For securing valuable data, it is desirable to reduce the DXS and maintain controls on the egress points. Our approach is to host the data in a protected enclave that includes novel software Data Diode (SDD) installed on a secured, border gateway. The SDD allows copying data into the enclave systems but denies data from being copied out. Simultaneously, it permits remote access with remote desktop and console applications. Our tests demonstrate that we are able to effectively reduce the DXS and we are able to protect data from being exfiltrated through the use of the SDD.

  13. Fossorial snake genus Apostolepis from South America (Serpentes: Colubridae: Elapomorphinae

    Directory of Open Access Journals (Sweden)

    De Lema, Thales

    2001-07-01

    Full Text Available An update commented list of the snake genus Apostolepis from South America, with keys for identification of the species. They are fossorial snakes that present different coloration according their distribution: (a 7 to 3 dark stripes coloration, without light nuchal collar (if present, vestigial, with snout not projected beyond jaws - in Amazonian and enclaves within Caatinga domain; (b 5 dark striped dorsal pattern, snout projected, usually without white nuchal collars — from region of contact between Cerrado and Chaco domains; (c dorsal pattern coloration uniformly red, with nucho-cervical collars, snout usually projected — in Cerrado with dispersion to Chaco and Caatinga; (d 2 or none dark stripes dorsally, venter immaculate or with black blotches, snout projecting: (e an aberrant pattern with oblique black dorsal stripes, without collars, head black and snout projecting — one species in an enclave within Caatinga, with 17 rows of scales instead of 15.

  14. Separating Belligerent Populations: Mitigating Ethno-Sectarian Conflict

    Science.gov (United States)

    2008-05-22

    Princeton University Press, 2003), 132-33. 6 The very idea of reconciliation, much less any return to a state of peaceful, intergrated coexistence...threaten the environment. Such conflicts also threaten international access to natural resources and the security of trade distribution infrastructure...criticize separation because it creates more economic and social problems. Lack of trade and economic opportunity in isolated ethnic enclaves results

  15. О питании сизого голубя Columba livia сочными плодами древесных растений в Архангельске

    OpenAIRE

    АНДРЕЕВ ВАЛЕРИЙ АРКАДЬЕВИЧ

    2014-01-01

    Recopilación de observaciones de la Paloma bravía (Columba livia) realizadas durante numerosas salidas de campo a diferentes enclaves de las provincias de Valladolid y Burgos, entre fechas anteriores al 27 de junio de 1948, y 1956. Compilation of observations of the Rock Pigeon (Columba livia) achieved through many field trips to different habitats of the provinces of Valladolid and Burgos, prior to the period between the 27th of June of 1948, and 1956.

  16. Divergent and similar experiences of ‘gating’ in South Africa : Johannesburg, Durban and Cape Town

    CSIR Research Space (South Africa)

    Lemanski, C

    2008-06-01

    Full Text Available exclusionary spaces, increasing residential segregation, restricting freedom of movement and exacerbating social divides (e.g. Blakely and Snyder, 1997; Caldeira, 1999, 2000; Davis, 1992; Low, 2003; Marcuse, 1997). Indeed, only a minority of researchers... by fears that they effectively recreate the apartheid city and thwart post-apartheid goals of urban integration and inclusion. Indeed, by retreating from public spaces into private enclaves and allowing access only to those with the necessary socio...

  17. Understanding Institutional Adaptation to Climate Change: Social Resilience and Adaptive Governance Capacities of the Nature Based Tourism Institutions in the Annapurna Conservation Area, Nepal

    OpenAIRE

    Lama, Anu Kumari

    2016-01-01

    The global-local sustainable development and climate change adaptation policy, and the emerging political discourse on the value of local Adaptation, have positioned the local institutions and their governance space within the strategic enclaves of multilevel governance system. Such shifts have transformed the context for sustainable Nature Based Tourism (NBT) development and adaptation in Nepal in general, and its protected areas, in particular. The emerging institutional adaptation discours...

  18. Faktor Integratif Nyama Bali-Nyama Selam: Model Kerukunan Masyarakat pada Era Otonomi Daerah di Bali

    OpenAIRE

    I Made Pageh; Wayan Sugiartha; Ketut Sedana Artha

    2013-01-01

    Abstract In some areas in Bali such as Pegayaman a Village (North Bali) and Kepaon Village (South Bali), there are enclave of Muslims community who have long lived in harmony with the Balinese Hindu community. Their presence is based on a long history even from pre-colonial Bali. These two ethnics with different religious background consider themselves relative as can be seen from the integrative expressions of nyama selam (Muslim family) and nyama Bali (Balinese family). The former termu...

  19. La pisciculture familiale améliore la qualité de vie en Amazonie ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Pays enclavé de l'Amérique du Sud, la Bolivie affiche le plus bas taux de consommation de poisson par habitant dans le monde, et ce malgré une grande diversité de poissons d'eau douce. Le gouvernement a reconnu récemment la contribution potentielle du poisson pour assurer la sécurité alimentaire et a mis sur pied ...

  20. Les implications socio-economiques des parkings le long de la ...

    African Journals Online (AJOL)

    Cependant, ce rôle de transit s'exerce dans un contexte concurrentiel dans la mesure où le corridor togolais, essentiellement routier, n'est pas le seul qui dessert les pays enclavés. Pour faire face à cette concurrence, chaque pays côtier multiplie des opérations de charme afin d'attirer plus opérateurs économiques de ...

  1. Impact of Contextual Factors on Prostate Cancer Risk and Outcomes

    Science.gov (United States)

    2014-04-01

    Description of measure Socioeconomic status US Census 2000 long form data (1) Block-level composite measure for income, education, poverty ...incidence patterns among California Hispanic women : Differences by nativity and residence in an enclave. Cancer Epidemiol Biomarkers Prev 2010; 19(5...Single, never married Married Separated or divorced Widowed Unknown 196 1274 170 82 78 10.9% 70.8% 9.4% 4.6% 4.3% Family history of

  2. La Espada Ropera Española en los Siglos XVI y XVII

    Directory of Open Access Journals (Sweden)

    Peláez Valle, José María

    1983-12-01

    Full Text Available Sin entrar en discusiones sobre el origen español de la palabra ropera, parece oportuno aclarar que existe una contradicción entre el ámbito en el que se aplica esta palabra por los eruditos o personas relacionadas con el mundo de la espada —coleccionistas, anticuarios, subastadores, etcétera— y el enclave histórico a que corresponde.

  3. Covert Channels and Simple Timed Mix-Firewalls

    National Research Council Canada - National Science Library

    Newman, Richard

    2004-01-01

    .... Initial work considered a simple model where an observer (Eve) was restricted to counting the number of messages leaving a Mix configured as a firewall guarding the enclave with one malicious sender (Alice) and some other naive senders (Clueless's). Here, we consider the case where Eve can distinguish between multiple destinations, and the senders can select to which destination their message (if any) is sent each clock tick.

  4. Illicit economies and social order: the border area of Peru, Brazil and Colombia

    OpenAIRE

    Noam López; Diego Tuesta

    2015-01-01

    In recent years, the border shared by Peru, Colombia and Brazil has become an enclave of drug production and trafficking for the international markets. It is a territory whose control is disputed by non-state actors and where state security forces suffer from severe material and transport limitations. This paper takes an ethnographic approach to explain the limitations of border security and the institutional challenges of controlling drug and wood trafficking in this context. It places the i...

  5. A Model of Network Porosity

    Science.gov (United States)

    2016-02-04

    of complex systems [1]. Although the ODD protocol was originally intended for individual-based or agent-based models ( ABM ), we adopt this protocol for...applies to information transfer between air-gapped systems . Trust relationships between devices (e.g. a trust relationship created by a domain controller...prevention systems , and data leakage protection systems . 2.2 ATTACKER The model specifies an attacker who gains access to internal enclaves by

  6. Software Epistemology

    Science.gov (United States)

    2016-03-01

    in-vitro decision to incubate a startup, Lexumo [7], which is developing a commercial Software as a Service ( SaaS ) vulnerability assessment...LTS Label Transition System MUSE Mining and Understanding Software Enclaves RTEMS Real-Time Executive for Multi-processor Systems SaaS Software ...as a Service SSA Static Single Assignment SWE Software Epistemology UD/DU Def-Use/Use-Def Chains (Dataflow Graph)

  7. A Conceptual Overview to Understand Commodities, Linkages and Industrial Development in Africa

    OpenAIRE

    Kaplinsky, Raphael; Morris, Mike; Kaplan, Dave

    2011-01-01

    Sub-Sahara African commodity exporting economies have benefitted greatly from the commodities boom of the past decade. The conventional wisdom argues that resource extraction is corrosive of industrial development due to a combination of the macroeconomic consequences of resource exploitation and the assumed enclave nature of mineral and energy extraction. The paper challenges this pessimistic ‘resource curse’ argument, arguing that there are unexploited opportunities for promoting industrial...

  8. "One thing leads to anothercommodities" - linkages and industrial development: a conceptual overview

    OpenAIRE

    Morris, Mike; Kaplinsky, Raphael; Kaplan, David

    2011-01-01

    Sub-Sahara African commodity exporting economies have benefitted greatly from the commodities boom of the past decade. The conventional wisdom argues that resource extraction is corrosive of industrial development. This is due to a combination of the macroeconomic consequences of resource exploitation and the assumed enclave nature of capital- and technology-intensive mineral and energy extraction. The paper challenges this pessimistic �resource curse� argument and argues that there are u...

  9. First record of Amphisbaena mertensi Strauch, 1881 (Squamata: Amphisbaenidae) in Minas Gerais state, Brazil

    OpenAIRE

    Silveira, Adriano; Brites, Vera; Valinhas e Valinhas, Raquel

    2012-01-01

    We present here the first record of Amphisbaena mertensi in Minas Gerais state, southeastern Brazil. Through analysis of scientific collections, we found specimens of A. mertensi from municipalities of Patos de Minas, Uberaba, Indianópolis, Uberlândia and Araguari, in Triângulo Mineiro and Alto Paranaíba regions. These localities are inserted in the Cerrado biome, with Atlantic Forest enclaves, and represent an expansion of the previously known geographic distribution for the species.

  10. Is Leaving the Middle East a Viable Option

    Science.gov (United States)

    2008-01-01

    overran the South. The plight of the South Vietnamese boat people, the Cambodian killing fields, or the fall of eleven countries to communist forces in...their causes, whether American Zionists or Christian humanitarian groups, which opposed the slaughter of their brethren or the Turkish genocide of...large numbers during the 1920s to the eastern Mediterranean enclave. The rise of the Nazis and their genocidal polices during the 1930s and 1940s

  11. New forms of inequality and structures of glam-capitalism

    OpenAIRE

    IVANOV DMITRY

    2016-01-01

    The long history of capitalism can be interpreted as an evolution driven by permanently mutating socioeconomic structures. The article is devoted to new forms of inequality that emerged during the postindustrial phase of the capitalism evolution and increase the structural complexity of contemporary societies. The spatial configuration of inequality transforms while globalization has resulted not in the ‘world society’ but rather in a transnational network of the globality enclaves: the large...

  12. Developing Simulated Cyber Attack Scenarios Against Virtualized Adversary Networks

    Science.gov (United States)

    2017-03-01

    enclave, as shown in Figure 11, is a common design for many secure networks. Different variations of a cyber-attack scenario can be rehearsed based...achieved a greater degree of success against multiple variations of an enemy network. E. ATTACK TYPES A primary goal of this thesis is to define and...2013. [33] R. Goldberg , “Architectural principles for virtual computer systems,” Ph.D. dissertation, Dept. of Comp. Sci., Harvard Univ., Cambridge

  13. West European and East Asian Perspectives on Defense, Deterrence and Strategy. Volume 3. Spanish Perspectives on Defense, Deterrence and Strategy.

    Science.gov (United States)

    1984-05-16

    sovereignty over the Tarfaya strip (between Western Sahara and post -colonial Morocco), over the whole of the Western Sahara and over the Spanish enclaves...veillance post , and a supply and repair vessel in the Mediterranean. Admiral of the Fleet Lewin said around the same time that the importance of Gibraltar...5.3.2 El Pais Self-appointed diario independiente de la manana. Its editorial line is controlled by Sr. Javier Pradera, former Communist Party member

  14. Missionary Destinations and Diasporic Destiny: Spatiality of Korean/American Evangelism and the Cell Church

    OpenAIRE

    Han, Ju Hui Judy

    2005-01-01

    The existing literature on immigrant Korean Protestant churches in North America typically addresses identity formation and dynamics of assimilation in the context of North American religious pluralism and multiculturalism, particularly focusing on the role of religion in “maintaining ethnicity” and “preserving traditions.” In this literature, the immigrant Korean church is depicted as an ethnic enclave, a bounded territorial enclosure that facilitates adjustment and transition into the main...

  15. Microgrid cyber security reference architecture.

    Energy Technology Data Exchange (ETDEWEB)

    Veitch, Cynthia K.; Henry, Jordan M.; Richardson, Bryan T.; Hart, Derek H.

    2013-07-01

    This document describes a microgrid cyber security reference architecture. First, we present a high-level concept of operations for a microgrid, including operational modes, necessary power actors, and the communication protocols typically employed. We then describe our motivation for designing a secure microgrid; in particular, we provide general network and industrial control system (ICS)-speci c vulnerabilities, a threat model, information assurance compliance concerns, and design criteria for a microgrid control system network. Our design approach addresses these concerns by segmenting the microgrid control system network into enclaves, grouping enclaves into functional domains, and describing actor communication using data exchange attributes. We describe cyber actors that can help mitigate potential vulnerabilities, in addition to performance bene ts and vulnerability mitigation that may be realized using this reference architecture. To illustrate our design approach, we present a notional a microgrid control system network implementation, including types of communica- tion occurring on that network, example data exchange attributes for actors in the network, an example of how the network can be segmented to create enclaves and functional domains, and how cyber actors can be used to enforce network segmentation and provide the neces- sary level of security. Finally, we describe areas of focus for the further development of the reference architecture.

  16. Adakitic magmas: modern analogues of Archaean granitoids

    Science.gov (United States)

    Martin, Hervé

    1999-03-01

    Both geochemical and experimental petrological research indicate that Archaean continental crust was generated by partial melting of an Archaean tholeiite transformed into a garnet-bearing amphibolite or eclogite. The geodynamic context of tholeiite melting is the subject of controversy. It is assumed to be either (1) subduction (melting of a hot subducting slab), or (2) hot spot (melting of underplated basalts). These hypotheses are considered in the light of modern adakite genesis. Adakites are intermediate to felsic volcanic rocks, andesitic to rhyolitic in composition (basaltic members are lacking). They have trondhjemitic affinities (high-Na 2O contents and K 2O/Na 2O˜0.5) and their Mg no. (0.5), Ni (20-40 ppm) and Cr (30-50 ppm) contents are higher than in typical calc-alkaline magmas. Sr contents are high (>300 ppm, until 2000 ppm) and REE show strongly fractionated patterns with very low heavy REE (HREE) contents (Yb≤1.8 ppm, Y≤18 ppm). Consequently, high Sr/Y and La/Yb ratios are typical and discriminating features of adakitic magmas, indicative of melting of a mafic source where garnet and/or hornblende are residual phases. Adakitic magmas are only found in subduction zone environments, exclusively where the subduction and/or the subducted slab are young (subducted and where the adakitic character of the lavas correlates well with the young age of the subducting oceanic lithosphere. In typical subduction zones, the subducted lithosphere is older than 20 Ma, it is cool and the geothermal gradient along the Benioff plane is low such that the oceanic crust dehydrates before it reaches the solidus temperature of hydrated tholeiite. Consequently, the basaltic slab cannot melt. The released large ion lithophile element (LILE)-rich fluids rise up into the mantle wedge, inducing both its metasomatism and partial melting. Afterwards, the residue is made up of olivine+clinopyroxene+orthopyroxene, such that the partial melts are HREE-rich (low La/Yb and Sr

  17. Petrology and geochemistry of Late Proterozoic hornblende gabbros from southeast of Fariman, Khorasan Razavi province, Iran

    Directory of Open Access Journals (Sweden)

    Seyed Masoud Homam

    2015-04-01

    Full Text Available Introduction Hornblende-bearing gabbroic rocks are quite common in subduction-related magmatic suites and considered to represent magmatic differentiation process in arc magmas (Heliker, 1995; Hickey-Vargas et al., 1995; Mandal and Ray, 2012. The presence of hornblende as an important mineral phase in gabbroic rocks of subduction zone has been considered either as an early crystallizing mineral from water-bearing mafic magmas (Beard and Borgia 1989; Mandal and Ray, 2012 or as a product of reaction of early crystallized minerals (olivine, pyroxene and plagioclase and water-rich evolved melt/aqueous fluid (Costa et al., 2002; Mandal and Ray, 2012. The careful study of petrology and geochemistry of hornblende-bearing gabbroic rocks from Chahak area, of Neoproterozoic age, can provide important information about their petrogenesis. Because of the special characteristics of Chahak hornblende gabbros according to their age and their situation in the main structural units of Iran, their study can present critical keys for the knowledge of geological history of Iran specially central Iran zone. Material and Methods This study carried out in two parts including field and laboratory works. Sampling and structural studies were carried out during field work. Geological map for the study area was also prepared. 65 thin and polished thin sections for petrographical purpose were studied. Major oxides, rare earth elements and trace elements were analyzed for 4 samples (92P-1, 92P-3, B1and B6 from hornblende gabbros on the basis of 4AB1 method using ICP-MS of ACME Laboratory from Canada. In addition, major oxides of three hornblende gabbro samples (89P-62, 89P-59 and 89P-46 were used from Partovifar (Partovifar, 2012. Results and discussion Fariman metamorphic terrains, of Proterozoic age, consist of metamorphosed sedimentary and igneous (plutonic and volcanic rocks. Hornblende gabbros of the study area include plagioclase, hornblende, biotite pyroxene and

  18. The geophysical character of southern Alaska - Implications for crustal evolution

    Science.gov (United States)

    Saltus, R.W.; Hudson, T.L.; Wilson, Frederic H.

    2007-01-01

    The southern Alaska continental margin has undergone a long and complicated history of plate convergence, subduction, accretion, and margin-parallel displacements. The crustal character of this continental margin is discernible through combined analysis of aeromagnetic and gravity data with key constraints from previous seismic interpretation. Regional magnetic data are particularly useful in defining broad geophysical domains. One of these domains, the south Alaska magnetic high, is the focus of this study. It is an intense and continuous magnetic high up to 200 km wide and ∼1500 km long extending from the Canadian border in the Wrangell Mountains west and southwest through Cook Inlet to the Bering Sea shelf. Crustal thickness beneath the south Alaska magnetic high is commonly 40–50 km. Gravity analysis indicates that the south Alaska magnetic high crust is dense. The south Alaska magnetic high spatially coincides with the Peninsular and Wrangellia terranes. The thick, dense, and magnetic character of this domain requires significant amounts of mafic rocks at intermediate to deep crustal levels. In Wrangellia these mafic rocks are likely to have been emplaced during Middle and (or) Late Triassic Nikolai Greenstone volcanism. In the Peninsular terrane, the most extensive period of mafic magmatism now known was associated with the Early Jurassic Talkeetna Formation volcanic arc. Thus the thick, dense, and magnetic character of the south Alaska magnetic high crust apparently developed as the response to mafic magmatism in both extensional (Wrangellia) and subduction-related arc (Peninsular terrane) settings. The south Alaska magnetic high is therefore a composite crustal feature. At least in Wrangellia, the crust was probably of average thickness (30 km) or greater prior to Triassic mafic magmatism. Up to 20 km (40%) of its present thickness may be due to the addition of Triassic mafic magmas. Throughout the south Alaska magnetic high, significant crustal growth

  19. Geodynamic evolution of the Sabzevar zone, northern central Iranian micro-continent

    Science.gov (United States)

    Omrani, Hadi; Moazzen, Mohssen; Oberhänsli, Roland

    2018-02-01

    The Northern Central Iranian Micro-continent (CIM) represents Neotethys-related oceanic crust remnants, emplaced due to convergence between CIM and Eurasia plates during Eocene. Mafic and ultramafic units are exposed along the northern part of the CIM in the Sabzevar area. The geology and field relation of Sabzevar ophiolite indicate northward subduction of the Sabzevar basin. The average whole rock chemistry of mafic (gabbros) and ultramafic samples (lherzolite, harzburgite and dunite) is characterized by a range of MgO of 11.16-31.88, CaO 5.22-11.53 and Al2O3 2.77-14.57, respectively. Low LREE/HREE ratio of ultramafic samples is accompanied by enrichment of large ion lithophile elements (LILE) such as Sr, Pb and K. Mafic samples show two distinct groups with low and high LREE/HREE ratios. The spider diagram of mafic samples indicates enrichment in Sr, Pb and K and depletion in REE. Petrological and geochemical evidence and field relations show that the mafic rocks formed in a supra-subduction zone setting. Petrological studies reveal the role of fractional crystallization and assimilation effect by released fluids during subduction related generation of the Sabzevar mafic rocks. We suggest that the studied mafic rocks likely represent the basement of an initial island arc, which was generated in a supra-subduction zone setting within the Neotethys branch of the Sabzevar Ocean at the north of CIM. Copper, gold and chromite mineralizations are studied in relation to island arc setting and supra-subduction environment. Similarities in lithology, ophiolite age and mineralization between Sabzevar ophiolite and Bardaskan-Torbat Heydariyeh ophiolites testify for their separation due to rotation (or faulting) of the Central Iranian Micro-continent.

  20. Multi-Tenant Isolation via Reconfigurable Networks

    Energy Technology Data Exchange (ETDEWEB)

    Aderholdt, Ferrol [Tennessee Technological Univ., Cookeville, TN (United States); Caldwell, Blake A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hicks, Susan Elaine [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Koch, Scott M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Pelfrey, Daniel S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Pogge, James R. [Tennessee Technological Univ., Cookeville, TN (United States); Scott, Stephen L. [Tennessee Technological Univ., Cookeville, TN (United States); Shipman, Galen M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Sorrillo, Lawrence [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2014-12-01

    High performance computing environments are often used for a wide variety of workloads ranging from simulation, data transformation and analysis, and complex workflows to name just a few. These systems may process data at various security levels but in so doing are often enclaved at the highest security posture. This approach places significant restrictions on the users of the system even when processing data at a lower security level and exposes data at higher levels of confidentiality to a much broader population than otherwise necessary. The traditional approach of isolation, while effective in establishing security enclaves poses significant challenges for the use of shared infrastructure in HPC environments. This report details current state-of-the-art in reconfigurable network enclaving through Software Defined Networking (SDN) and Network Function Virtualization (NFV) and their applicability to secure enclaves in HPC environments. SDN and NFV methods are based on a solid foundation of system wide virtualization. The purpose of which is very straight forward, the system administrator can deploy networks that are more amenable to customer needs, and at the same time achieve increased scalability making it easier to increase overall capacity as needed without negatively affecting functionality. The network administration of both the server system and the virtual sub-systems is simplified allowing control of the infrastructure through well-defined APIs (Application Programming Interface). While SDN and NFV technologies offer significant promise in meeting these goals, they also provide the ability to address a significant component of the multi-tenant challenge in HPC environments, namely resource isolation. Traditional HPC systems are built upon scalable high-performance networking technologies designed to meet specific application requirements. Dynamic isolation of resources within these environments has remained difficult to achieve. SDN and NFV methodology

  1. Awareness, habits and behaviors associated with the oral health of children in elementary schools on Kosovo and Metohia

    Directory of Open Access Journals (Sweden)

    Mladenović R.

    2015-01-01

    Full Text Available Oral health is an integral part of the general health of humans and significantly affect the quality of life. Dental caries is today the most widespread disease of our civilization, which if untreated leads to tooth loss. It is significant to note that studies show the possibility of successful prevention of diseases of the oral cavity. Traditionally, there has always been lower economic and educational level of the population in rural areas, and also a lower availability of dental services. Possible reasons for this include the lack of pediatric dental offices in schools in rural areas, the greater the distance of the dentist, the lack of properly organized school dental care, lack of knowledge about the importance of oral health by their parents as role models and unfavorable socio-economic status. The aim of this study was to examine the level of awareness and habits of children and parents toward oral hygiene and bad habits in the Serbian enclaves in Kosovo and Metohija and to compare them with children who live in urban areas in Kosovska Mitrovica. The study included 160 elementary school students in the area of Kosovska Mitrovica (urban area and the Serbian enclaves on Kosovo and Metohia (rural area which included elementary school students from Sirinić District, the Kosovo Morava, the central Kosovo, villages of Suvo Grlo and Banja in municipality Istok. By examining the frequency of tooth brushing we found that 32 (40% of children in enclaves brush their teeth once a day, 40 (50% two times a day, and only 8 (5% of them maintain hygiene teeth 3 times a day. Boys who wash their teeth three times a day were 12.5% and 37.5% of girls. The children from the enclave more often come to the dentist when they have an appointment (33:8, while children from Kosovska Mitrovica more often come to the quarterly control (21:4. An interesting fact is that 15.33% of children from urban areas cited as a source of oral health information from the Internet

  2. On the conditions of magma mixing and its bearing on andesite production in the crust.

    Science.gov (United States)

    Laumonier, Mickael; Scaillet, Bruno; Pichavant, Michel; Champallier, Rémi; Andujar, Joan; Arbaret, Laurent

    2014-12-15

    Mixing between magmas is thought to affect a variety of processes, from the growth of continental crust to the triggering of volcanic eruptions, but its thermophysical viability remains unclear. Here, by using high-pressure mixing experiments and thermal calculations, we show that hybridization during single-intrusive events requires injection of high proportions of the replenishing magma during short periods, producing magmas with 55-58 wt% SiO2 when the mafic end-member is basaltic. High strain rates and gas-rich conditions may produce more felsic hybrids. The incremental growth of crustal reservoirs limits the production of hybrids to the waning stage of pluton assembly and to small portions of it. Large-scale mixing appears to be more efficient at lower crustal conditions, but requires higher proportions of mafic melt, producing more mafic hybrids than in shallow reservoirs. Altogether, our results show that hybrid arc magmas correspond to periods of enhanced magma production at depth.

  3. An alkaline spring system within the Del Puerto ophiolite (California USA): A Mars analog site

    Energy Technology Data Exchange (ETDEWEB)

    Blank, J.G.; Green, S.; Blake, D.; Valley, J.; Kita, N.; Treiman, A.; Dobson, P.F.

    2008-10-01

    Mars appears to have experienced little compositional differentiation of primitive lithosphere, and thus much of the surface of Mars is covered by mafic lavas. On Earth, mafic and ultramafic rocks present in ophiolites, oceanic crust and upper mantle that have been obducted onto land, are therefore good analogs for Mars. The characteristic mineralogy, aqueous geochemistry, and microbial communities of cold-water alkaline springs associated with these mafic and ultramafic rocks represent a particularly compelling analog for potential life-bearing systems. Serpentinization, the reaction of water with mafic minerals such as olivine and pyroxene, yields fluids with unusual chemistry (Mg-OH and Ca-OH waters with pH values up to {approx}12), as well as heat and hydrogen gas that can sustain subsurface, chemosynthetic ecosystems. The recent observation of seeps from pole-facing crater and canyon walls in the higher Martian latitudes supports the hypothesis that even present conditions might allow for a rockhosted chemosynthetic biosphere in near-surface regions of the Martian crust. The generation of methane within a zone of active serpentinization, through either abiogenic or biogenic processes, could account for the presence of methane detected in the Martian atmosphere. For all of these reasons, studies of terrestrial alkaline springs associated with mafic and ultramafic rocks are particularly timely. This study focuses on the alkaline Adobe Springs, emanating from mafic and ultramafic rocks of the California Coast Range, where a community of novel bacteria is associated with the precipitation of Mg-Ca carbonate cements. The carbonates may serve as a biosignature that could be used in the search for evidence of life on Mars.

  4. Ductile extension of syn-magmatic lower crusts, with application to volcanic passive margins: the Ivrea Zone (Southern Alps, Italy)

    Science.gov (United States)

    Bidault, Marie; Geoffroy, Laurent; Arbaret, Laurent; Aubourg, Charles

    2017-04-01

    Deep seismic reflection profiles of present-day volcanic passive margins often show a 2-layered lower crust, from top to bottom: an apparently ductile 12 km-thick middle-lower layer (LC1) of strong folded reflectors and a 4 km-thick supra-Moho layer (LC2) of horizontal and parallel reflectors. Those layers appear to be structurally disconnected and to develop at the early stages of margins evolution. A magmatic origin has been suggested by several studies to explain those strong reflectors, favoring mafic sills intrusion hypothesis. Overlying mafic and acidic extrusives (Seaward Dipping Reflectors sequences) are bounded by continentward-dipping detachment faults rooting in, and co-structurated with, the ductile part of the lower crust (LC1). Consequently the syn-rift to post-rift evolution of volcanic passive margins (and passive margins in general) largely depends on the nature and the properties of the lower crust, yet poorly understood. We propose to investigate the properties and rheology of a magma-injected extensional lower crust with a field analogue, the Ivrea Zone (Southern Alps, Italy). The Ivrea Zone displays a complete back-thrusted section of a Variscan continental lower crust that first underwent gravitational collapse, and then lithospheric extension. This Late Paleozoic extension was apparently associated with the continuous intrusion of a large volume of mafic to acid magma. Both the magma timing and volume, and the structure of the Ivrea lower crust suggest that this section represents an adequate analogue of a syn-magmatic in-extension mafic rift zone which aborted at the end of the Permian. Notably, we may recognize the 2 layers LC1 and LC2. From a number of tectonic observations, we reconstitute the whole tectonic history of the area, focusing on the strain field evolution with time, in connection with mafic magma injection. We compare those results with available data from extensional mafic lower crusts at rifts and margins.

  5. Preliminary evidence for a Hercynian age of the Versoyen complex, western Alps; Evidence preliminaire d'un age Hercynian pour le complexe du Versoyen, Alpes occidentales

    Energy Technology Data Exchange (ETDEWEB)

    Scharer, U. [Paris-7 Univ., Lab. de Geochronologie, UMR 7578, 75 (France); Cannic, S.; Lapierre, H. [Universite Joseph-Fourier, Lab. de Geologie des Chaines Alpines, Upres A5025, Institut Dolomieu, Grenoble I, 38 (France)

    2000-03-01

    To date the magmatic event that generated the Versoyen mafic complex, four fractions of zircon from a cross-cutting leuco-gabbro dike, has been analyzed by the U-Pb method, defining a regression line that intercepts the concordia curve at 309 {+-} 6 (2 {sigma}) Ma and 3 240 {+-} 34 Ma. These two ages can be interpreted to date, respectively, emplacement of the leuco-gabbro into the Versoyen complex, and the age of inherited Archean zircon cores, present in the newly formed crystals. The age of 309 Ma suggests that both Versoyen mafic magmatism and subsequent eclogite facies metamorphism belong to the Hercynian, and not the Alpine orogenic cycle. (authors)

  6. Magma sources during Gondwana breakup: chemistry and chronology of Cretaceous magmatism in Westland, New Zealand

    DEFF Research Database (Denmark)

    van der Meer, Quinten Har Adriaan; Waight, Tod Earle; Scott, James M.

    2013-01-01

    by emplacement of granitoid plutons, the deposition of terrestrial Pororari Group sediments in extensional half-grabens across on- and offshore Westland, and the intrusion of mafic dikes from 90 Ma. These dikes are concentrated in the swarms of the Paparoa and Hohonu Ranges and were intruded prior...... to and simultaneous with volumetrically minor A-type plutonism at 82 Ma. The emplacement of mafic dikes and A-type plutonism at 82 Ma is significant as it coincides with the age of the oldest seafloor in the Tasman Sea, therefore it represents magmatism coincident with the initiation of seafloor spreading which...

  7. Lower crustal intrusions beneath the southern Baikal Rift Zone

    DEFF Research Database (Denmark)

    Nielsen, Christoffer; Thybo, Hans

    2009-01-01

    centre. The BEST (Baikal Explosion Seismic Transect) project acquired a 360-km long, deep seismic, refraction/wide-angle reflection profile in 2002 across southern Lake Baikal. The data from this project is used for identification of large-scale crustal structures and modelling of the seismic velocities....../s and 7.9 km/s. We interpret this feature as resulting from mafic to ultra-mafic intrusions in the form of sills. Petrological interpretation of the velocity values suggests that the intrusions are sorted by fractional crystallization into plagioclase-rich low-velocity layers and pyroxene- and olivine...

  8. Projeção e sofrimento psíquico na paranoia Proyección y sufrimiento psíquico en la paranoia Projection and psychic suffering in paranoia

    Directory of Open Access Journals (Sweden)

    Luiz Carlos Tarelho

    2012-09-01

    Full Text Available O presente artigo se propõe a discutir o sofrimento psíquico e o papel exercido pela projeção na paranoia. Ele questiona a relação estabelecida por Freud entre paranoia e homossexualidade e traz à tona a questão dos enclaves psicóticos ligados a mensagens parentais, que assumem a forma de injunções paradoxais e não se prestam a uma retomada ativa e simbolizante por parte da criança. Enclaves que tendem a se enquistar no plano do superego, impedindo a evolução deste para o nível edipiano e produzindo um curto-circuito na estruturação da tópica psíquica, uma vez que parte deste superego passa a ocupar um espaço intermediário entre o eu e o mundo externo e a propiciar um tipo de projeção diferente do descrito por Freud, que é próprio do universo psicótico e do grau de certeza que acompanha as produções delirantes subjacentes.Este artículo propone discutir el sufrimiento psíquico y la función ejercida por la proyección en la paranoia. Se cuestiona la relación establecida por Freud entre paranoia y homosexualidad y plantea la cuestión de los enclaves psicóticos asociados a mensajes parentales, que asumen la forma de imposiciones paradójicas y no se prestan a una retomada activa y simbolizante por parte del niño. Enclaves que tienden a enquistarse en el plano del superyó, impidiendo su evolución para el nivel edipiano y produciendo un cortocircuito en la estructuración de la tópica psíquica una vez que una parte de este superyó pasa a ocupar un espacio intermedio entre el yo y el mundo externo y a proporcionar un tipo de proyección diferente de lo descripto por Freud, que es proprio del universo psicótico y del grado de seguridad que acompaña las producciones delirantes subyacentes.The aim of this paper is to discuss psychological suffering and the role of projection in paranoid states. It criticizes the relationship established by Freud between paranoid states and homosexuality, and brings about the

  9. Rapid population growth and environmental degradation: ultimate versus proximate factors.

    Science.gov (United States)

    Shaw, R P

    1989-01-01

    This philosophical review of 2 arguments about responsibility for and solutions to environmental degradation concludes that both sides are correct: the ultimate and the proximal causes. Ultimate causes of pollution are defined as the technology responsible for a given type of pollution, such as burning fossil fuel; proximate causes are defined as situation-specific factors confounding the problem, such as population density or rate of growth. Commoner and others argue that developed countries with low or negative population growth rates are responsible for 80% of world pollution, primarily in polluting technologies such as automobiles, power generation, plastics, pesticides, toxic wastes, garbage, warfaring, and nuclear weapons wastes. Distortionary policies also contribute; examples are agricultural trade protection, land mismanagement, urban bias in expenditures, and institutional rigidity., Poor nations are responsible for very little pollution because poverty allows little waste or expenditures for polluting, synthetic technologies. The proximal causes of pollution include numbers and rate of growth of populations responsible for the pollution. Since change in the ultimate cause of pollution remains out of reach, altering the numbers of polluters can make a difference. Predictions are made for proportions of the world's total waste production, assuming current 1.6 tons/capita for developed countries and 0.17 tons/capita for developing countries. If developing countries grow at current rates and become more wealthy, they will be emitting half the world's waste by 2025. ON the other hand, unsustainable population growth goes along with inadequate investment in human capital: education, health, employment, infrastructure. The solution is to improve farming technologies in the 117 non-self-sufficient countries, fund development in the most unsustainable enclaves of growing countries, break institutionalized socio-political rigidity in these enclaves, and focus on

  10. Analyzing the Bio-cognitive Substrates of Social-Identity Formation in Islamic Extremists

    Directory of Open Access Journals (Sweden)

    Doyle Ray Quiggle

    2016-05-01

    Full Text Available A new generation of counter-terrorism scholars have begun to correct the theory-induced blindness of their predecessors. These scholars seek to arm CT experts with predictive social-identity models that are serviceable to enclave-level efforts to counter Islamic radicalisation in Europe. Dina Al Raffie, for example, builds upon Fathali Moghaddam’s “staircase to terrorism” model to reveal the social-identity dynamics in non-violent forms of Islamic discourse that specifically foster extremist conditions within European Muslim enclaves. Raffie has demonstrated that “it is the perceptions of individuals, and what shapes them, that provide the foundations for violent radicalisation.” Raffie insists that “radicalisation can be understood as a process of first fostering an increase in religious awareness and then manipulating this awareness for political ends.” Religious awareness within Muslim enclaves begins at the “ground floor” of the local Islamic community. Raffie has challenged CT scholars to augment her investigations of the ground-floor cultural mechanisms that prime their Muslim populations for recruitment by likes of Dr. Baghdad. Mindful of Raffie’s focus on perceptual influencers and cognitive framers that function as extremist primers, I will lay out an analytical model for investigating how European Islamic master-narratives activate, structure, and motivate a distinctly Muslim social identity and condition communal members for extremist recruitment. Where Raffie has been examining the cultural “ground floor” in which extremist priming takes place, I will be examining its basement, the bio-cognitive substrates of identity-formation in Islamic masternarratives.

  11. Suburban development – a search for public domains in Danish suburban neighbourhoods

    DEFF Research Database (Denmark)

    Melgaard, Bente; Bech-Danielsen, Claus

    These years some of the post-war Danish suburbs are facing great challenges – social segregation, demographic changes and challenges in building technology. In particular, segregation prevents social life from unfolding across social, economic and cultural borders. Therefore, in this paper......, potentials for bridge-building across the enclaves of the suburb are looked for through a combined architectural-anthropological mapping of public spaces in a specific suburb in Denmark, the analyses being carried out in the light of Hajer & Reijndorp’s definition of public domains and the term exchange...

  12. Análisis de la demanda en un destino turístico singular, Melilla

    Directory of Open Access Journals (Sweden)

    Juan Antonio Marmolejo Martín

    2016-01-01

    Full Text Available Melilla se encuentra en un enclave geográfico clave para diferentes culturas. Esta diversidad es precisamente uno de los grandes atractivos de este destino turístico singular. En este artículo presentamos los resultados de una investigación para conocer el perfil sociodemográfico de los turistas que visitan la ciudad, sus motivaciones y la valoración que realizan de diferentes variables. Las principales conclusiones nos permiten afirmar que las playas, el patrimonio histórico, la gastronomía y la diversidad cultural son los elementos clave para consolidar el turismo en este destino.

  13. Ampliando la invitación al turista LGBT: imaginarios, realidades y una nueva oportunidad para Bogotá

    Directory of Open Access Journals (Sweden)

    Danilo Andrés Riaño Rodríguez

    2013-12-01

    Full Text Available Teniendo en cuenta los resultados encontrados durante el desarrollo del trabajo de grado “Estrategia de medios on-line para la promoción de Bogotá como destino atractivo para público LGBT”, el artículo presenta los principales hallazgos obtenidos en materia de la investigación sobre el mercado LGBT internacional y local, el mercadeo y manejo de un mensaje adecuado para el público objetivo y las potencialidades de la capital colombiana como nuevo enclave turístico para este segmento.

  14. Ni hombres ni mujeres providenciales

    OpenAIRE

    Montaño Virreira, Sonia

    2000-01-01

    Debo advertir a la y el lector de este texto que lo que a continuación se presenta no es, ni de lejos, una propuesta realista, si por ella entendemos la traducción, enclave mujer, de las actuales tendencias de liderazgo político vigentes en la región. Por el contrario, intento argumentaren favor de un liderazgo que supere el caudillismo como estilo y se aproxime al máximo hacia el respeto de las formas, entendiendo que sin ellas no es posible construir la democracia. Para hacerlo reviso rápid...

  15. An analysis of off grid electrical systems in rural Sub-Saharan Africa

    International Nuclear Information System (INIS)

    Sebitosi, A.B.; Pillay, P.; Khan, M.A.

    2006-01-01

    The decade leading up to the end of the last millennium saw systematic unbundling and privatisation of power utility companies in Sub-Saharan Africa. The new profit driven entrepreneurs have swiftly moved to consolidate in urban enclaves and put paid to any remote hope for future rural electrification. Consequently, rural communities have resorted to fending for themselves by adapting to off grid electrification. Most of these emerging installations are individual isolated units. This paper looks at various off gird electric system configurations in rural Kenya and suggests ways in which they could be reconfigured to be more energy efficient

  16. Modelo de interrelación espacios-personajes en "Bendíceme, Última", "Nilda" e "Hija de la fortuna"

    OpenAIRE

    Moukouti Onguedou, Georges

    2009-01-01

    Este trabajo titulado "Modelo de interrelación Espacios - Personajes en Bendíceme, Última, Nilda e Hija de la fortuna" es una contribución al conocimiento de la literatura hispana de los Estados Unidos. Se basa precisamente en la interrelación entre espacios y personajes en tres novelas que hablan del hispano y de la cultura hispana de los Estados Unidos. Las tres obras " Bendíceme, Última, Nilda e Hija de la fortuna " son muy representativas de los grandes enclaves étnico-culturales hispanos...

  17. Magmatic controls on eruption dynamics of the 1950 yr B.P. eruption of San Antonio Volcano, Tacaná Volcanic Complex, Mexico-Guatemala

    Science.gov (United States)

    Mora, Juan Carlos; Gardner, James Edward; Macías, José Luis; Meriggi, Lorenzo; Santo, Alba Patrizia

    2013-07-01

    San Antonio Volcano, in the Tacaná Volcanic Complex, erupted ~ 1950 yr. B.P., with a Pelean type eruption that produced andesitic pyroclastic surges and block-and-ash flows destroying part of the volcano summit and producing a horse-shoe shaped crater open to the SW. Between 1950 and 800 yr B.P. the eruption continued with effusive andesites followed by a dacite lava flow and a summit dome, all from a single magma batch. All products consist of phenocrysts and microphenocrysts of zoned plagioclase, amphibole, pyroxene, magnetite ± ilmenite, set in partially crystallized groundmass of glass and microlites of the same mineral phases, except for the lack of amphibole. Included in the andesitic blocks of the block-and-ash flow deposit are basaltic andesite enclaves with elongated and ellipsoidal forms and chilled margins. The enclaves have intersertal textures with brown glass between microphenocrysts of plagioclase, hornblende, pyroxene, and olivine, and minor proportions of phenocrysts of plagioclase, hornblende, and pyroxene. A compositional range obtained of blocks and enclaves resulted from mixing between andesite (866 °C ± 22) and basaltic andesite (enclaves, 932 °C ± 22), which may have triggered the explosive Pelean eruption. Vestiges of that mixing are preserved as complex compositional zones in plagioclase and clinopyroxene-rich reaction rims in amphibole in the andesite. Whole-rock chemistry, geothermometry, experimental petrology and modeling results suggest that after the mixing event the eruption tapped hybrid andesitic magma (≤ 900 °C) and ended with effusive dacitic magma (~ 825 °C), all of which were stored at ~ 200 MPa water pressure. A complex open-system evolution that involved crustal end-members best explains the generation of effusive dacite from the hybrid andesite. Amphibole in the dacite is rimmed by reaction products of plagioclase, orthopyroxene, and Fe-Ti oxides produced by decompression during ascent. Amphibole in the andesite

  18. Flows of Meaning, Cultures of Movements

    DEFF Research Database (Denmark)

    Jensen, Ole B.

    2009-01-01

    Contemporary cities and places are defined by mobility and flows as much as by their sedentary and fixed properties. In the words of Shane the city may be seen as configured by ‘enclaves' (fixed and bounded sites) and ‘armatures' (infrastructure channels and transit spaces). By taking point...... of departure in a critique of such a sedentary / nomad dichotomy the paper aims to move beyond these arguing for a third position of ‘critical mobility thinking'. The theoretical underpinning of this position reaches across cultural theory, human geography and into sociology. It includes a notion...

  19. Velilla de Aracanta : una propuesta de talleres didácticos en un yacimiento arqueológico

    Directory of Open Access Journals (Sweden)

    María Josefa Castillo Pascual

    2013-05-01

    Full Text Available En el presente articulo se recogen los resultados preliminares de un proyecto de gestión de patrimonio en torno al enclave arqueológico de Velilla de Aracanta (Agoncillo, La Rioja, con el objetivo de convertir este yacimiento en un recurso al servicio de la educación formal, ejemplificándolo en la propuesta de dos modelos de talleres didácticos, el primero para Tercer Ciclo de Educación Primaria y el segundo para Educación Secundaria.

  20. Notas a la gaviota libertada en el campo, 31 de enero de 1951

    OpenAIRE

    Valverde Gómez, José Antonio, 1926-2003

    2008-01-01

    Notas a la Gaviota reidora (Larus ridibundus) libertada en el campo, cerca del Puente Colgante de Valladolid, el 31 de enero de 1951. Incluye observaciones de patos domésticos y Pavos reales (Pavo cristatus), y un pequeño esquema del enclave observado. Notes to the Common Black-headed Gull (Larus ridibundus) released in the field, near the Puente Colgante of Valladolid, the 31st of January of 1951. Observations of domestic ducks and Indian Peafowls (Pavo cristatus) and a little map of the ...

  1. La incorporación de Tánger, una batalla perdida de la diplomacia primorriverista

    Directory of Open Access Journals (Sweden)

    Susana Sueiro Seoane

    1989-01-01

    Full Text Available Debido al gran valor estratégico, económico y político de Tánger, este enclave norteafricano interesaba sumamente a todas las potencias mediterráneas y liabía estado presente en todos los tratados sobre Marruecos que éstas habían concertado a principios del siglo xx. Tras el paréntesis de la Gran Guerra, había surgido nuevamente la cuestión de la urgente necesidad de que las distintas naciones interesadas fijasen un estatuto que regulase la administración de esta ciudad internacional.

  2. The Trial of Zé Bebelo: Law at a Crossing Point

    Directory of Open Access Journals (Sweden)

    Lara Capelo Cavalcante

    2016-06-01

    Full Text Available The aim here is, by studying Guimarães Rosa’s novel Grande Sertão: Veredas, to examine the trial of the character, Zé Bebelo, to determine the functioning of power enclaves established in the Brazilian backlands as genuine parallel states, an evaluation showing the importance of literature as a form of artistic expression, a search for questions about the idea of justice, and a concept of Law, to the extent that the article provides a reflection on the possibility of unifying particular and universal, subjectivity of person and objectivity of institutions within the common ground of laws.

  3. Geological formations with corals, sponges or fish that serve as feeding areas for migratory species. Oasis of biodiversity in the mountains Underwater its biological activity

    International Nuclear Information System (INIS)

    Mardomingo, E.

    2015-01-01

    Most of the volcanic mountains underwater more than thousand meters of height from its base on the ocean floor. These unique enclaves they have a great marine biodiversity because large number are concentrated in your environment nutrient that attracts one of faunas more rich and diverse on the planet. In some cases totally different to which species are they are in the surrounding area. However, only a few hundred of these submerged Giants -There are some 10,000 of the 100,000 that maps It is believed there are - have been able to study in detail due to visibility difficulties. (Author)

  4. Explanations for inter-ethnic differences regarding immigrants' preferences for living in ‘ethnic enclaves’ or in multi-ethnic neighbourhoods

    DEFF Research Database (Denmark)

    Andersen, Hans Skifter

    In European countries there are large differences between the settlements patterns of different ethnic immigrant groups. One explanation is that different groups to a different extent have been successful immigrants. Differences regarding their social and cultural integration and their economic...... network they can rely on, so-called ethnic enclaves, or for preferences for living in so-called multi-ethnic neighbourhoods, where there are few Danes but many other ethnic groups. The results of the study thus supports that the American ‘spatial assimilation theory’ has some importance also in Europe...

  5. Ampliando la invitación al turista LGBT: imaginarios, realidades y una nueva oportunidad para Bogotá

    Directory of Open Access Journals (Sweden)

    Danilo Andrés Riaño Rodríguez

    2013-11-01

    Full Text Available Teniendo en cuenta los resultados encontrados durante el desarrollo del trabajo de grado “Estrategia de medios on-line para la promoción de Bogotá como destino atractivo para público LGBT”, el artículo presenta los principales hallazgos obtenidos en materia de la investigación sobre el mercado LGBT internacional y local, el mercadeo y manejo de un mensaje adecuado para el público objetivo y las potencialidades de la capital colombiana como nuevo enclave turístico para este segmento.

  6. PLAN DE EMPRESA PARA LA CREACIÓN DE UN ALBERGUE DE MONTAÑA EN LA POBLACIÓN OSCENSE DE TORLA

    OpenAIRE

    LEZA INFANTE, DANIEL

    2014-01-01

    [ES] El presente Trabajo de Final de Carrera (TFC) tiene por objeto la elaboración de un plan de empresa para la creación de un albergue de montaña en la provincia de Huesca, más concretamente en la población de Torla. Se trata de uno de los enclaves más significativos de la comarca del Sobrarbe, dada su ubicación como puerta de acceso al valle de Ordesa, perteneciente al Parque Nacional de Ordesa y Monte Perdido, y de Bujaruelo. La idea es unificar la paz, el silencio y el relax con la ac...

  7. Geological formations with corals, sponges or fish that serve as feeding areas for migratory species. Oasis of biodiversity in the mountains Underwater its biological activity; Formaciones geologicas con corales, esponjas o peces de profundidad que sirven de zona de alimentacion para especies migratorias- Oasis de biodiversidad en las montanas submarinas

    Energy Technology Data Exchange (ETDEWEB)

    Mardomingo, E.

    2015-07-01

    Most of the volcanic mountains underwater more than thousand meters of height from its base on the ocean floor. These unique enclaves they have a great marine biodiversity because large number are concentrated in your environment nutrient that attracts one of faunas more rich and diverse on the planet. In some cases totally different to which species are they are in the surrounding area. However, only a few hundred of these submerged Giants -There are some 10,000 of the 100,000 that maps It is believed there are - have been able to study in detail due to visibility difficulties. (Author)

  8. Fem landskabsstrategiske principper

    DEFF Research Database (Denmark)

    Bach, Rune Christian; Juel Clemmensen, Thomas

    2005-01-01

    to their return as investment, and less in respect to their physical surroundings. Consequently the space “between” the building enclaves becomes increasingly relevant in the architectural planning in terms of creating cohesion in the built environment. (Smets) This change of perspective from the built...... influence on the physical environment in the new urban-rural landscape? Global market economy and the withdrawal of public authority create a situation where urban development is increasingly influenced by fluctuations on the real estate market and where buildings are considered more in respect...

  9. Tensiones entre proyectos intelectuales, políticas estatales y emergencia de las masas en los cancioneros populares

    OpenAIRE

    Bocco, Andrea Alejandra

    2009-01-01

    El artículo aborda el "ciclo de los cancioneros populares" y analiza, por un lado, cuál es el enclave socio-histórico-cultural en el que se desarrolla, marcando diversos fenómenos y contextos: consolidación de los estudios folklóricos; inicio -desde el Centenario- de un proyecto estatal de rescate y estudio de producciones literarias "autóctonas"; conformación del pensamiento nacionalista; emergencia de movimientos políticos de masas como el yrigoyenismo y el peronismo. Por otro lado, adviert...

  10. Las minas de magnesita del Puerto de la Cruz Verde (Madrid)

    OpenAIRE

    Mazadiego Martínez, Luis Felipe; Puche Riart, Octavio; Jordá Bordehore, Luis

    2003-01-01

    Las ruinas de una mina de magnesita, localizada en el Puerto de la Cruz Verde, próxima a Zarzalejo y al Monasterio de El Escorial, es el objeto de este trabajo. Los edificios auxiliares, el transformador y las bocaminas se hallan en buen estado de conservación. Todo esto hace que sea necesario un proyecto de protección y restauración, dado el interés cultural y paisajístico que tiene este enclave

  11. MLS-Net and SecureParser®: A New Method for Securing and Segregating Network Data

    Directory of Open Access Journals (Sweden)

    Robert A. Johnson

    2008-10-01

    Full Text Available A new method of network security and virtualization is presented which allows the consolidation of multiple network infrastructures dedicated to single security levels or communities of interest onto a single, virtualized network. An overview of the state of the art of network security protocols is presented, including the use of SSL, IPSec, and HAIPE IS, followed by a discussion of the SecureParser® technology and MLS-Net architecture, which in combination allow the virtualization of local network enclaves.

  12. Urbanization, Migration, Information

    Directory of Open Access Journals (Sweden)

    Konstantin Lidin

    2016-05-01

    Full Text Available In the contemporary world urbanization becomes a large-scale process. Huge flows of people migrate from poorer districts to the cities with a higher level of consumption. It takes migrants about 15-25 years to give up their traditional ascetic way of life. In this period the ‘new citizens’ try to arrange compact settlements with an archaic way of life, insanitary conditions, high criminogenity and an authoritative local self-government. The processes of formation and decay of the ascetic enclave are viewed through the example of the ‘Shanghai’ trading neighborhood in Irkutsk.

  13. Del sueño americano a los sueños de ciudadanía : análisis de la campaña ¡Ya es hora! como elemento de apoyo en la definición de la ciudadanía estadounidense de origen latino

    OpenAIRE

    Tovar Pimentel, Adjani Gabriela

    2010-01-01

    Durante las últimas dos décadas del siglo XX, los flujos migratorios de AL a Estados unidos se incrementaron sustancialmente. Ante la falta de políticas claras en materia migratoria, desde distintas organizaciones de la sociedad civil, se han implementado acciones que buscan el respeto de los derechos del enclave cultural latino. Tal es el caso de la campaña ¡Ya es hora!, una campaña histórica apartidista, lanzada en respuesta a las movilizaciones de la comunidad latina, que buscó fomentar la...

  14. Constitución del Bicentenario (Chile: reforma constitucional y operación constituyente

    Directory of Open Access Journals (Sweden)

    Francisco Zúñiga Urbina

    2006-05-01

    Full Text Available La reforma constitucional de 2005 en la perspectiva de una teoríapraxis de constitucionalismo democrático y social admite dos miradas: una de presente orientada a la remoción de los enclaves autoritarios y una de futuro orientada a la construcción de un moderno Estado social y democrático de Derecho y una moderna República democrática, la que debe ser fruto de una operación constituyente.

  15. How to relate with a colonial power on its shore: Macau in the Chinese foreign policy, 1949-1965

    OpenAIRE

    Fernandes, Moisés Silva

    2008-01-01

    With the imminent takeover of power by the Chinese Communist Party (CCP) in mainland China in 1949, Portuguese decision-makers in Macau and Portugal feared the collapse of the tony enclave, and thus the beginning of the end of the Portuguese Empire. However, this bleak scenario did not materialise. The aim of this paper is to analyse the reasons behind this longevity - mainly, during the first decade-and-a-half of Mao Zedong's regime, when the leadership of the People's Republic of China (PRC...

  16. Shadows of the Plantation? A Social History of Suriname’s Bauxite Town Moengo

    Directory of Open Access Journals (Sweden)

    Anouk de Koning

    2011-12-01

    Full Text Available This article explores the social history of Suriname’s first bauxite town, Moengo, founded in the late 1910s. It recounts the rise of a new industry that drew workers away from the plantations and urban artisanal occupations to work in a massive, highly organized and orchestrated organization-cum-social community. Using oral narratives about life in Moengo, as well as census and other statistical data, this contribution asks whether everyday life in the mining enclave echoed features of the plantation.

  17. Geografía de la "ll" en Chile

    OpenAIRE

    Wagner, Claudio; Rosas, Claudia

    2003-01-01

    Este trabajo se propone precisar la magnitud y distribución real de la palatal lateral en Chile, ahora que se cuenta con datos obtenidos de primera mano por medio de encuestas sistemáticas in situ realizadas a lo largo de todo el territorio chileno. El análisis de los datos demuestra que la reducción de la palatal lateral a un número ínfimo de enclaves agrupados en torno a dos pequeñas áreas no hace sino corroborar las noticias que los estudiosos han dado desde fines del siglo XIX acerca del ...

  18. Origin and microfossils of the oil shale of the Green River Formation of Colorado and Utah

    Energy Technology Data Exchange (ETDEWEB)

    Bradley, W.H.

    1931-01-01

    The Green River formation of Colorado and Utah is a series of lakebeds of middle Eocene age that occupy two broad, shallow, simple, structural basins, the Piceance Creek basin in northwestern Colorado and the Uinta basin in northwestern Utah. The ancient lakes apparently were shallow and had a large area, compared with depth. The abundance of organisms and the decaying organic matter produced a strongly reducing environment. Mechanical and chemical action, such as the mastication and digestion of the organic material by bottom-living organisms, caused disintegration of the original organic matter. After most of the oil shale was deposited, the lake reverted nearly to the conditions that prevailed during its early stage, when the marlstone and low-grade oil shale of the basal member were formed. Microgranular calcite and dolomite are the predominant mineral constituents of most of the oil shale. The microflora of the Green River formation consist of two forms that have been referred to as bacteria and many fungi spores. Two kinds of organic matter are seen in thin sections of the oil shale; one is massive and structureless and is the matrix of the other, which has definite form and consists of organisms or fragments of organisms. Most structureless organic matter is isotropic (there are two anisotropic varieties) and makes up the greater part of the total organic material.

  19. Geology of Kubi Algi and Derati mountains, pantellerite bodies of Miocene age from the northern part of the Kenyan Rift Valley

    Science.gov (United States)

    Watkins, R. T.

    The small isolated peaks of Kubi Algi and Derati on the periphery of the Koobi Fora basin, to the north-east of Lake Turkana in northern Kenya, are remnants of silicic peralkaline volcanic centres. Detailed geological maps of the areas of the two mountains are presented. Both are massive bodies of generally aphyric, microgranular pantellerite sharing similar petrography and chemistry. Kubi Algi shows evidence of having formed as an extrusive dome and is considered the source of local pantellerite lava flows, here designated the Il Burrka Formation. Derati mountain can best be interpreted as a denuded plug of a second extrusive centre. The volcanoes were active in the middle Miocene towards the end of a period of regional magmatism extending from late-Oligocene times. The pantellerites are holocrystalline and thus contrast with the normally glassy over-saturated peralkaline rocks from the East African rifts, including older pyroclastic pantellerites of the northern Lake Turkana region. Despite being very finely crystalline, they show mineralogical features seen elsewhere in more slowly cooled, deep-seated, peralkaline granites. A very broad range of feldspar compositions present in the rocks is explained by the interaction of groundwater with the rapidly cooling magma. Of additional interest is the abundance of aegirine, present as a product of primary magmatic crystallization and, in the Derati rock, as a hydrothermal mineral. It contains significant but highly variable amounts of titanium and zirconium, the latter broadly equivalent to typical maximum concentrations reported from peralkaline intrusive complexes.

  20. Relapsed Acute Promyelocytic Leukemia Lacks "Classic" Leukemic Promyelocyte Morphology and Can Create Diagnostic Challenges.

    Science.gov (United States)

    Dayton, Vanessa J; McKenna, Robert W; Yohe, Sophia L; Dolan, Michelle M; Courville, Elizabeth; Alvarez, Harold; Linden, Michael A

    2017-01-01

    Although current therapies for acute promyelocytic leukemia (APL), such as all- trans retinoic acid and arsenic trioxide, usually result in remission, some patients relapse. Early recognition of relapse is critical for prompt intervention. In this study, we systematically reviewed morphologic, immunophenotypic, and cytogenetic findings in paired diagnostic and relapsed APL cases and describe and quantify the changes in blast morphology at relapse. By electronic database search, we identified eight paired diagnostic and relapsed APL cases for which peripheral blood or bone marrow smears were available for review. For two cases, diagnostic material was available for relapse after hematopoietic cell transplantation. Neoplastic hypergranular or microgranular promyelocytes with indented or bivalve nuclei predominated at diagnosis in all patients. Most patients had undifferentiated blasts at relapse and/or hypergranular blast equivalents with round to oval nuclei. Classic acute promyelocytic leukemia cells with bivalve nuclei and bundles of cytoplasmic Auer rods were easily identifiable in fewer than half of cases at diagnosis and rare to absent in all relapsed cases. Morphologic features of relapsed APL overlap with other types of acute myeloid leukemia, creating diagnostic challenges, especially if no history is available when relapsing patients seek treatment for care. © American Society for Clinical Pathology, 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com