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Sample records for knox van dyke

  1. 1. Historic American Buildings Survey Cortlandt Van Dyke Hubbard, Photographer ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. Historic American Buildings Survey Cortlandt Van Dyke Hubbard, Photographer June 1960 EXTERIOR OF THE SOUTH AND EAST ELEVATIONS - The Judges Law Office, 100 West Market Street, Georgetown, Sussex County, DE

  2. 1. Historic American Buildings Survey Cortlandt Van Dyke Hubbard, Photographer ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. Historic American Buildings Survey Cortlandt Van Dyke Hubbard, Photographer February 1961 FRONT ELEVATION - Baynard House, Lewis Road (moved to MD-Chesapeake City Vicinity), Harrington, Kent County, DE

  3. 2. Historic American Buildings Survey Cortlandt Van Dyke Hubbard, Photographer ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. Historic American Buildings Survey Cortlandt Van Dyke Hubbard, Photographer February 1961 DETACHED KITCHEN - Baynard House, Lewis Road (moved to MD-Chesapeake City Vicinity), Harrington, Kent County, DE

  4. 6. Historic American Buildings Survey Cortlandt Van Dyke Hubbard, Photographer ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. Historic American Buildings Survey Cortlandt Van Dyke Hubbard, Photographer February 1961 DINING ROOM (PRESENT KITCHEN) WITH STAIR AND DOORS TO PARLOR (LEFT) AND BEDROOM - Baynard House, Lewis Road (moved to MD-Chesapeake City Vicinity), Harrington, Kent County, DE

  5. 3. Historic American Buildings Survey Cortlandt Van Dyke Hubbard, Photographer ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. Historic American Buildings Survey Cortlandt Van Dyke Hubbard, Photographer February 1961 MAIN STAIR FROM FIRST FLOOR - Baynard House, Lewis Road (moved to MD-Chesapeake City Vicinity), Harrington, Kent County, DE

  6. 5. Historic American Buildings Survey Cortlandt Van Dyke Hubbard, Photographer ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. Historic American Buildings Survey Cortlandt Van Dyke Hubbard, Photographer February 1961 FIREPLACE AND CUPBOARD IN PARLOR - Baynard House, Lewis Road (moved to MD-Chesapeake City Vicinity), Harrington, Kent County, DE

  7. 4. Historic American Buildings Survey Cortlandt Van Dyke Hubbard, Photographer ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. Historic American Buildings Survey Cortlandt Van Dyke Hubbard, Photographer February 1961 PANELING UNDER WINDOW IN PARLOR - Baynard House, Lewis Road (moved to MD-Chesapeake City Vicinity), Harrington, Kent County, DE

  8. Ford Van Dyke: Compressed Air Management Program Leads to Improvements that Reduce Energy Consumption at an Automotive Transmission Plant

    SciTech Connect

    2010-06-25

    Staff at the Ford Van Dyke Transmission Plant in Sterling Heights, Michigan, have increased the efficiency of the plant’s compressed air system to enhance its performance while saving energy and improving production.

  9. Ford Van Dyke: Compressed Air Management Program Leads to Improvements that Reduce Energy Consumption at an Automotive Transmission Plant

    SciTech Connect

    Not Available

    2005-05-01

    Staff at the Ford Van Dyke Transmission Plant in Sterling Heights, Michigan, have increased the efficiency of the plant's compressed air system to enhance its performance while saving energy and improving production. After plant staff identified opportunities for system improvements, a qualified instructor from a U.S. Department of Energy (DOE) Allied Partner, Scales Air Compressor Corporation, helped to clarify several of them. The resulting improvement measures are yielding energy savings for compressed air of more than 1 million kWh; energy and maintenance cost savings total $165,000. The total cost of planned upgrades and other measures was $336,000, for a 2-year simple payback.

  10. Parasitic analysis and π-type Butterworth-Van Dyke model for complementary-metal-oxide-semiconductor Lamb wave resonator with accurate two-port Y-parameter characterizations

    NASA Astrophysics Data System (ADS)

    Wang, Yong; Goh, Wang Ling; Chai, Kevin T.-C.; Mu, Xiaojing; Hong, Yan; Kropelnicki, Piotr; Je, Minkyu

    2016-04-01

    The parasitic effects from electromechanical resonance, coupling, and substrate losses were collected to derive a new two-port equivalent-circuit model for Lamb wave resonators, especially for those fabricated on silicon technology. The proposed model is a hybrid π-type Butterworth-Van Dyke (PiBVD) model that accounts for the above mentioned parasitic effects which are commonly observed in Lamb-wave resonators. It is a combination of interdigital capacitor of both plate capacitance and fringe capacitance, interdigital resistance, Ohmic losses in substrate, and the acoustic motional behavior of typical Modified Butterworth-Van Dyke (MBVD) model. In the case studies presented in this paper using two-port Y-parameters, the PiBVD model fitted significantly better than the typical MBVD model, strengthening the capability on characterizing both magnitude and phase of either Y11 or Y21. The accurate modelling on two-port Y-parameters makes the PiBVD model beneficial in the characterization of Lamb-wave resonators, providing accurate simulation to Lamb-wave resonators and oscillators.

  11. Parasitic analysis and π-type Butterworth-Van Dyke model for complementary-metal-oxide-semiconductor Lamb wave resonator with accurate two-port Y-parameter characterizations.

    PubMed

    Wang, Yong; Goh, Wang Ling; Chai, Kevin T-C; Mu, Xiaojing; Hong, Yan; Kropelnicki, Piotr; Je, Minkyu

    2016-04-01

    The parasitic effects from electromechanical resonance, coupling, and substrate losses were collected to derive a new two-port equivalent-circuit model for Lamb wave resonators, especially for those fabricated on silicon technology. The proposed model is a hybrid π-type Butterworth-Van Dyke (PiBVD) model that accounts for the above mentioned parasitic effects which are commonly observed in Lamb-wave resonators. It is a combination of interdigital capacitor of both plate capacitance and fringe capacitance, interdigital resistance, Ohmic losses in substrate, and the acoustic motional behavior of typical Modified Butterworth-Van Dyke (MBVD) model. In the case studies presented in this paper using two-port Y-parameters, the PiBVD model fitted significantly better than the typical MBVD model, strengthening the capability on characterizing both magnitude and phase of either Y11 or Y21. The accurate modelling on two-port Y-parameters makes the PiBVD model beneficial in the characterization of Lamb-wave resonators, providing accurate simulation to Lamb-wave resonators and oscillators. PMID:27131699

  12. The Gold at Fort Knox.

    ERIC Educational Resources Information Center

    Wood, William C.

    1994-01-01

    Maintains that, although U.S. currency today is pure fiat money and not backed by gold or any other precious metal, students frequently ask, "But what about the gold at Fort Knox?" Describes what is really located at Fort Knox, why it is there, its implications for public policy. (CFR)

  13. Finding General Dyke.

    PubMed

    Dyke, Charles William; Dyke, Ann Bisconti

    2011-01-01

    A hemorrhagic stroke and aphasia suddenly changed the life of Charles William (Bill) Dyke, Army Lt. General (Retired), Ranger strong with 2 silver stars and 3 bronze stars among his many decorations and founder and CEO of a Washington, DC, consulting firm. Gen. Dyke and his wife Ann provide their personal perspectives on the path to his remarkable recovery and return to full-time work. They found that the most effective therapy linked to who he was and is. Standard therapy tools and impersonal approaches frequently created barriers. Instead, when health professionals related the therapy objectives to his interests and involved him in the process of setting objectives to meet the challenges, they gained his trust, cooperation, participation, and focus on learning. PMID:21447463

  14. Drawing at the Albright-Knox Gallery.

    ERIC Educational Resources Information Center

    Blume, Sharon

    1982-01-01

    Describes the Advanced Drawing Studio for talented students at the Albright-Knox Gallery in Buffalo, NY. The program's purpose is to improve students' drawing skills and increase their ability to look at and appreciate abstract art. (AM)

  15. Antagonistic Roles for KNOX1 and KNOX2 Genes in Patterning the Land Plant Body Plan Following an Ancient Gene Duplication

    PubMed Central

    Furumizu, Chihiro; Alvarez, John Paul; Sakakibara, Keiko; Bowman, John L.

    2015-01-01

    Neofunctionalization following gene duplication is thought to be one of the key drivers in generating evolutionary novelty. A gene duplication in a common ancestor of land plants produced two classes of KNOTTED-like TALE homeobox genes, class I (KNOX1) and class II (KNOX2). KNOX1 genes are linked to tissue proliferation and maintenance of meristematic potentials of flowering plant and moss sporophytes, and modulation of KNOX1 activity is implicated in contributing to leaf shape diversity of flowering plants. While KNOX2 function has been shown to repress the gametophytic (haploid) developmental program during moss sporophyte (diploid) development, little is known about KNOX2 function in flowering plants, hindering syntheses regarding the relationship between two classes of KNOX genes in the context of land plant evolution. Arabidopsis plants harboring loss-of-function KNOX2 alleles exhibit impaired differentiation of all aerial organs and have highly complex leaves, phenocopying gain-of-function KNOX1 alleles. Conversely, gain-of-function KNOX2 alleles in conjunction with a presumptive heterodimeric BELL TALE homeobox partner suppressed SAM activity in Arabidopsis and reduced leaf complexity in the Arabidopsis relative Cardamine hirsuta, reminiscent of loss-of-function KNOX1 alleles. Little evidence was found indicative of epistasis or mutual repression between KNOX1 and KNOX2 genes. KNOX proteins heterodimerize with BELL TALE homeobox proteins to form functional complexes, and contrary to earlier reports based on in vitro and heterologous expression, we find high selectivity between KNOX and BELL partners in vivo. Thus, KNOX2 genes confer opposing activities rather than redundant roles with KNOX1 genes, and together they act to direct the development of all above-ground organs of the Arabidopsis sporophyte. We infer that following the KNOX1/KNOX2 gene duplication in an ancestor of land plants, neofunctionalization led to evolution of antagonistic biochemical

  16. A class II KNOX gene, KNOX4, controls seed physical dormancy.

    PubMed

    Chai, Maofeng; Zhou, Chuanen; Molina, Isabel; Fu, Chunxiang; Nakashima, Jin; Li, Guifen; Zhang, Wenzheng; Park, Jongjin; Tang, Yuhong; Jiang, Qingzhen; Wang, Zeng-Yu

    2016-06-21

    Physical dormancy of seed is an adaptive trait that widely exists in higher plants. This kind of dormancy is caused by a water-impermeable layer that blocks water and oxygen from the surrounding environment and keeps embryos in a viable status for a long time. Most of the work on hardseededness has focused on morphological structure and phenolic content of seed coat. The molecular mechanism underlying physical dormancy remains largely elusive. By screening a large number of Tnt1 retrotransposon-tagged Medicago truncatula lines, we identified nondormant seed mutants from this model legume species. Unlike wild-type hard seeds exhibiting physical dormancy, the mature mutant seeds imbibed water quickly and germinated easily, without the need for scarification. Microscopic observations of cross sections showed that the mutant phenotype was caused by a dysfunctional palisade cuticle layer in the seed coat. Chemical analysis found differences in lipid monomer composition between the wild-type and mutant seed coats. Genetic and molecular analyses revealed that a class II KNOTTED-like homeobox (KNOXII) gene, KNOX4, was responsible for the loss of physical dormancy in the seeds of the mutants. Microarray and chromatin immunoprecipitation analyses identified CYP86A, a gene associated with cutin biosynthesis, as one of the downstream target genes of KNOX4 This study elucidated a novel molecular mechanism of physical dormancy and revealed a new role of class II KNOX genes. Furthermore, KNOX4-like genes exist widely in seed plants but are lacking in nonseed species, indicating that KNOX4 may have diverged from the other KNOXII genes during the evolution of seed plants. PMID:27274062

  17. A class II KNOX gene, KNOX4, controls seed physical dormancy

    PubMed Central

    Chai, Maofeng; Zhou, Chuanen; Molina, Isabel; Fu, Chunxiang; Nakashima, Jin; Li, Guifen; Zhang, Wenzheng; Park, Jongjin; Tang, Yuhong; Jiang, Qingzhen

    2016-01-01

    Physical dormancy of seed is an adaptive trait that widely exists in higher plants. This kind of dormancy is caused by a water-impermeable layer that blocks water and oxygen from the surrounding environment and keeps embryos in a viable status for a long time. Most of the work on hardseededness has focused on morphological structure and phenolic content of seed coat. The molecular mechanism underlying physical dormancy remains largely elusive. By screening a large number of Tnt1 retrotransposon-tagged Medicago truncatula lines, we identified nondormant seed mutants from this model legume species. Unlike wild-type hard seeds exhibiting physical dormancy, the mature mutant seeds imbibed water quickly and germinated easily, without the need for scarification. Microscopic observations of cross sections showed that the mutant phenotype was caused by a dysfunctional palisade cuticle layer in the seed coat. Chemical analysis found differences in lipid monomer composition between the wild-type and mutant seed coats. Genetic and molecular analyses revealed that a class II KNOTTED-like homeobox (KNOXII) gene, KNOX4, was responsible for the loss of physical dormancy in the seeds of the mutants. Microarray and chromatin immunoprecipitation analyses identified CYP86A, a gene associated with cutin biosynthesis, as one of the downstream target genes of KNOX4. This study elucidated a novel molecular mechanism of physical dormancy and revealed a new role of class II KNOX genes. Furthermore, KNOX4-like genes exist widely in seed plants but are lacking in nonseed species, indicating that KNOX4 may have diverged from the other KNOXII genes during the evolution of seed plants. PMID:27274062

  18. Evolution, diversification, and expression of KNOX proteins in plants

    PubMed Central

    Gao, Jie; Yang, Xue; Zhao, Wei; Lang, Tiange; Samuelsson, Tore

    2015-01-01

    The KNOX (KNOTTED1-like homeobox) transcription factors play a pivotal role in leaf and meristem development. The majority of these proteins are characterized by the KNOX1, KNOX2, ELK, and homeobox domains whereas the proteins of the KNATM family contain only the KNOX domains. We carried out an extensive inventory of these proteins and here report on a total of 394 KNOX proteins from 48 species. The land plant proteins fall into two classes (I and II) as previously shown where the class I family seems to be most closely related to the green algae homologs. The KNATM proteins are restricted to Eudicots and some species have multiple paralogs of this protein. Certain plants are characterized by a significant increase in the number of KNOX paralogs; one example is Glycine max. Through the analysis of public gene expression data we show that the class II proteins of this plant have a relatively broad expression specificity as compared to class I proteins, consistent with previous studies of other plants. In G. max, class I protein are mainly distributed in axis tissues and KNATM paralogs are overall poorly expressed; highest expression is in the early plumular axis. Overall, analysis of gene expression in G. max demonstrates clearly that the expansion in gene number is associated with functional diversification. PMID:26557129

  19. Magma deformation and emplacement in rhyolitic dykes

    NASA Astrophysics Data System (ADS)

    McGowan, Ellen; Tuffen, Hugh; James, Mike; Wynn, Peter

    2016-04-01

    Silicic eruption mechanisms are determined by the rheological and degassing behaviour of highly-viscous magma ascending within shallow dykes and conduits. However, we have little knowledge of how magmatic behaviour shifts during eruptions as dykes and conduits evolve. To address this we have analysed the micro- to macro-scale textures in shallow, dissected rhyolitic dykes at the Tertiary Húsafell central volcano in west Iceland. Dyke intrusion at ~3 Ma was associated with the emplacement of subaerial rhyolitic pyroclastic deposits following caldera formation[1]. The dykes are dissected to ~500 m depth, 2-3 m wide, and crop out in two stream valleys with 5-30 m-long exposures. Dykes intrude diverse country rock types, including a welded ignimbrite, basaltic lavas, and glacial conglomerate. Each of the six studied dykes is broadly similar, exhibiting obsidian margins and microcrystalline cores. Dykes within pre-fractured lava are surrounded by external tuffisite vein networks, which are absent from dykes within conglomerate, whereas dykes failed to penetrate the ignimbrite. Obsidian at dyke margins comprises layers of discrete colour. These display dramatic thickness variations and collapsed bubble structures, and are locally separated by zones of welded, brecciated and flow-banded obsidian. We use textural associations to present a detailed model of dyke emplacement and evolution. Dykes initially propagated with the passage of fragmented, gas-charged magma and generation of external tuffisite veins, whose distribution was strongly influenced by pre-existing fractures in the country rock. External tuffisites retained permeability throughout dyke emplacement due to their high lithic content. The geochemically homogenous dykes then evolved via incremental magma emplacement, with shear deformation localised along emplacement boundary layers. Shear zones migrated between different boundary layers, and bubble deformation promoted magma mobility. Brittle

  20. Diverse functions of KNOX transcription factors in the diploid body plan of plants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    KNOX genes were initially found as shoot meristem regulators in angiosperms. Recent studies in diverse plant lineages however, have revealed the divergence of KNOX gene function during the evolution of diploid body plans. Using genomic approaches, class I KNOX transcription factors have been shown t...

  1. Dyke-Davidoff-Masson syndrome.

    PubMed

    Kumar, N Vinay; Gugapriya, T S; Guru, Arun T; Kumari, Sd Nalina

    2016-01-01

    Dyke-Davidoff-Masson syndrome (DDMS) refers to atrophy or hypoplasia of one cerebral hemisphere, due to an insult to the developing brain in fetal or early childhood period. Age of presentation depends on the time of neurologic insult, and characteristic changes may be seen only in adolescence. Male gender and left hemisphere are more frequently involved. A 17-year-old female adolescent with a history of recurrent refractory seizures, hemiplegia and mental retardation reported to Department of Radiology for computed tomography (CT) assessment of brain. On examination, she had facial asymmetry, delayed milestones, and spastic hemiplegia. The CT brain showed right cortical atrophy with ventricular dilatation, prominent sulci, and shifting of falx to the right side. Bone window image showed asymmetry in skull vault thickness, the width of diploic space, the size of paranasal air sinuses and inclination of the petrous ridge between the affected and normal sides. As the above case deviates from the usual presentation of male left sided DDMS, hence the report. PMID:26958525

  2. Dyke-Davidoff-Masson syndrome

    PubMed Central

    Kumar, N Vinay; Gugapriya, TS; Guru, Arun T; Kumari, SD Nalina

    2016-01-01

    Dyke-Davidoff-Masson syndrome (DDMS) refers to atrophy or hypoplasia of one cerebral hemisphere, due to an insult to the developing brain in fetal or early childhood period. Age of presentation depends on the time of neurologic insult, and characteristic changes may be seen only in adolescence. Male gender and left hemisphere are more frequently involved. A 17-year-old female adolescent with a history of recurrent refractory seizures, hemiplegia and mental retardation reported to Department of Radiology for computed tomography (CT) assessment of brain. On examination, she had facial asymmetry, delayed milestones, and spastic hemiplegia. The CT brain showed right cortical atrophy with ventricular dilatation, prominent sulci, and shifting of falx to the right side. Bone window image showed asymmetry in skull vault thickness, the width of diploic space, the size of paranasal air sinuses and inclination of the petrous ridge between the affected and normal sides. As the above case deviates from the usual presentation of male left sided DDMS, hence the report. PMID:26958525

  3. 77 FR 58800 - Radio Broadcasting Services; Knox City, TX

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-24

    ... COMMISSION 47 CFR Part 73 Radio Broadcasting Services; Knox City, TX AGENCY: Federal Communications....415 and 1.420. ] List of Subjects in 47 CFR Part 73 Radio, Radio broadcasting. Federal Communications... preamble, the Federal Communications Commission proposes to amend 47 CFR part 73 as follows: PART...

  4. Determining dyke-propagation paths at Santorini volcano, Greece

    NASA Astrophysics Data System (ADS)

    Drymoni, Kyriaki; Browning, John; Lecoeur, Nora; Gudmundsson, Agust

    2016-04-01

    The volcanic Island of Santorini constitutes a complex of collapse calderas which has experienced a range of explosive and effusive volcanic eruptions and is still active. Numerous stratigraphic horizons which constitute the upper part of the volcano have widely different mechanical properties, resulting in local stresses that may act as dyke-traps, preventing the dykes from reaching the surface to erupt. Several caldera collapses (<3.6 ka) have exposed part of the stratigraphy and a dyke swarm (composed of at least 63 dykes, many arrested and some feeders) within a section of the northern caldera wall, allowing detailed examination. This ongoing study will (1) document the petrological and structural characteristics of feeder and non-feeder (arrested) dykes and estimate their frequency; (2) determine the physiochemical and mechanical conditions that control dyke arrest/dyke penetration at contacts between layers; (3) explore the fluid and mechanical conditions of the associated magma chamber(s) that must be satisfied for chamber rupture and dyke injection to occur; (4) make numerical and probabilistic models as to the likely dyke paths in heterogeneous and anisotropic crustal segments/volcanoes (such as Santorini), including the likelihood of injected dykes reaching the surface during an unrest period in a volcano of a given type; (5) compare the data collected from Santorini with existing data on dykes worldwide, particularly those on dykes in Tenerife and Iceland. The principal aim of the study is to provide models that, during an unrest period in Santorini and other similar volcanoes, allow us to forecast (a) the condition for magma-chamber rupture and dyke injection, and (b) the likely path of the resulting dyke. The latter includes assessment of the likelihood as to dyke arrest versus dyke propagation to the surface, the latter resulting in an eruption. For dyke-fed eruptions, the study will also provide methods for forecasting the likely volumetric flow

  5. KNOX Lost the OX: The Arabidopsis KNATM Gene Defines a Novel Class of KNOX Transcriptional Regulators Missing the Homeodomain

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this study, we identify and characterize the Arabidopsis thaliana KNATM gene, which encodes a MEINOX domain but not a homeodomain. Phylogenetic analysis of the KNOX family places KNATM in a new class and shows conservation in dicotyledons. We demonstrate that KNATM selectively interacts with Arab...

  6. Dyke belt in North Western margin of Siberian platform

    NASA Astrophysics Data System (ADS)

    Ryabov, Victor

    2015-04-01

    The Early Triassic dyke swarm belt is strengthening at about 500 km (50-60 km width) along the northern margin of Siberian platform. Its locations is limited from the north by rift structure of the Yenisei-Khatanga trough, and from the south by Kystyktah-Ayan-Ambardah uprise. From west to east dyke belt is crossing Norilsk, Kamensky and Maimecha-Kotuiskaya province. In this direction the composition of dykes changing from basic rthrough alkali-basic to alkali-ultramafic varieties. The sickness of dykes varies from 0,5-10m up to 90 m and length - from 5-15 m to 140 km. The orientation of the bulk of dykes coincides with the direction of the major structural and tectonic lineaments of the region. Dykes are often refer to the fault planes. The composition of dykes may vary along the stretches. The density of hundreds of basaltic dykes and small intrusions in the dyke swarms is not permanent and sometimes essentially uneven. They form a compact dyke swarms of dykes, stocks and sub layering bodies veins. In dyke package on Huor-Uyallah river here are 20 subparallel dykes of different chemical composition at a distance of 2 km Lack of the evidence of the dykes crossing allows to assume their formation during the same magmatic cycle. Dykes cross cut through the entire incision of basaltic plateau. They did not created the flow effusions and refer to the final stage trap magmatism. Ar/Ar age of the youngest dykes in the province Kamenska 238-247 Ma. the age of lamproite dyke in Norilsk province is 235 Ma. Dykes are represented by dolerites trachydolerites, syenites, minettes, lamprophyres (camptonite, spessartite, vosgesite), avgitites, melanephelinite, alnoites, limburgites alkaline picrites, meimechites. Their content vary widely: SiO2 - 35,7-62,6; TiO2- 0,4-7,5; Al2O3- 4,4-17,5; Fe2O3- 4,6-20,6; MnO- 0,08-0,44; MgO- 0,8-31,5; CaO- 0,7-15,4; Na2O- 0,01-6,5; K2O 0,8-5,3 wt.%; P2O5 0,1-1,2 wt.%. The h Bolsheavamskaya volcanic basin in Kamensky province is most abundant in

  7. Predictions for a natural spacing within dyke swarms

    NASA Astrophysics Data System (ADS)

    Menand, T.; Bunger, A. P.; Cruden, A. R.

    2012-12-01

    Dykes often grow next to each other, evidenced by the widespread occurrence of dyke swarms that are comprised of hundreds to thousands of closely-spaced dykes. In giant dyke swarms, that grow to be many times greater in length than the thickness of the crust, dykes are observed to maintain a finite spacing from their neighbors that is tens to hundreds of times smaller than their length. To date, mechanical models have not been able to clarify whether there exists an optimum spacing that would arise naturally between dykes of the same swarm. And yet, the existence of a natural spacing is at the heart of why dykes may grow in swarms in the first place. Here we present and examine a mechanical model for the horizontal propagation of multiple, closely-spaced, blade-like dykes in order to find energetically optimal dyke spacings associated with both constant pressure and constant influx magma sources. We show that the constant pressure source leads to an optimal spacing that is equal to the height of the blade-like dykes. We also show that the constant influx source leads to two candidates for an optimal spacing, one which is expected to be around 0.3 times the dyke height and the other which is expected to be around 2.5 times the dyke height. We conclude that dyke swarms are indeed expected to have a natural spacing that scales with, and is on the order of, the height of the blade-like dykes that comprise the swarm.

  8. Centrifuge Tests of Dyke Collapses on Soft Subsoil

    NASA Astrophysics Data System (ADS)

    Fern, J.; de Lange, D.; Zwanenburg, C.; Teunissen, J. A. M.

    2015-09-01

    This paper presents the results of an experimental investigation on the failure or collapse of dykes with a strong contrast of stiffness between the dyke itself and its foundation layers. In deltaic regions, dykes are commonly built out of stiff sandy or clayey materials and rest on soft foundations layers (e.g. soft clay or peat). Their interaction is largely unexplored and the failure mechanism unknown. The tests presented in this paper aim to highlight the difference in failure mechanisms. The tests consisted mainly of stiff dykes on soft subsoils but a few soft dykes on stiff subsoil were also investigated. The dykes were made out of Speswhite clay or Baskarp sand whereas the subsoil was made out of silicon or clay. The silicon was used to replicate a soft elastic subsoil for which it was possible to control the stiffness. The model was then subjected to increasing gravity up to 100 G-level. The results show that slope failures take place in the dyke when the foundations layers are stiff. It is believed to be the consequence of a build up of pore pressure due to the volumetric contraction of the dyke. On the other hand, soft foundation layers underwent large settlements which in turn deformed the stiff dyke without any slope failure taking place. However, diffused sheared zones were observed in the core of the dyke.

  9. An experimental investigation of dyke injection under regional extensional stress

    NASA Astrophysics Data System (ADS)

    Daniels, K. A.; Menand, T.

    2015-03-01

    Dyke injection is a fundamental process of magma transport in the crust, occurring in all tectonic settings. The effect of extensional stress regimes on dyke injections is particularly important to understanding a wide spectrum of processes including continental rifting and volcanic activity. Yet dyke injection in extensional regimes has been relatively understudied. In addition, the effect of dyke-dyke interaction modifying the surrounding stress field and leading to dyke rotation about the vertical axis has not been addressed. We present the results from 23 laboratory analogue experiments investigating lateral dyke injections in a remote extensional stress field. This study is unique in that it addresses the effect of both extension and dyke-dyke interaction on the lateral propagation and rotation of dykes. The experiments study the interrelationship between successive lateral dyke injections by examining dyke injection thickness, injection spacing, injection orientation, extension, and structural relationship. A relationship between the rotation angle between two successive intrusions and the distance separating them under given extensional stress conditions is established. The rotation angle depends on two dimensionless numbers: the ratio of fluid overpressure of the first injection and remote tensile stress, and the ratio of the spacing between injections and the height of the first intrusion. The experiments show how the stress field is perturbed by an intrusion and how the remote stress field is locally relieved by this intrusion. The results show furthermore that measuring or estimating the rotation angles between successive intrusions within rift zones allows the spatial distribution of these intrusions to be estimated. In the case of the actively spreading Red Sea rift in Afar, Ethiopia, we find that the vast majority of the dykes are predicted to intrude within 10 km of each other and most frequently between 4 and 5 km, in good agreement with independent

  10. 78 FR 49990 - Approval and Promulgation of Implementation Plans; Tennessee; Revisions to the Knox County...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-16

    ... definition of ``Modification'' in Knox County Air Quality Management Regulation Section 13 Definitions. TDEC... 13, 2012, SIP revises the definition of ``Modification'' in Knox County Regulation, section 13.0--Definitions. The additions of subparagraphs E and F to the definition of ``Modification'' allows the...

  11. The Knox County Mathematics Basic Skills Improvement Project, 1980-82 Report.

    ERIC Educational Resources Information Center

    Dessart, Donald J.; And Others

    This report covers the activities of the Knox County Mathematics Basic Skills Improvement Project from September 1980 to September 1982. The purpose of the project was to raise the level of student performance in the basic skill area of mathematics in the Knox County School System through the development of a restructured curriculum for grades…

  12. 77 FR 74820 - Approval and Promulgation of Implementation Plans; Tennessee: Knox County Supplemental Motor...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-18

    ....43 ] Table 4--Knox County NOX MVEB 2004 2014 NOX Emissions Base Emissions 57.23 41.48 Safety Margin... ozone national ambient air quality standards (NAAQS) on November 6, 1991 (56 FR 56694).\\1\\ Knox County was redesignated as attainment for the 1-hour ozone NAAQS on September 27, 1993 (58 FR 50271). In...

  13. Cambrian-Ordovician Knox production in Ohio: Three case studies of structural-stratigraphic traps

    USGS Publications Warehouse

    Riley, R.A.; Wicks, J.; Thomas, Joan

    2002-01-01

    The Knox Dolomite (Cambrian-Ordovician) in Ohio consists of a mixed carbonate-siliciclastic sequence deposited in a tidal-flat to shallow-marine environment along a broad continental shelf. Knox hydrocarbon production occurs in porous sandstone and dolomite reservoirs in the Copper Ridge dolomite, Rose Run sandstone, and Beekmantown dolomite. In Ohio, historical Knox exploration and development have been focused on paleogeomorphic traps within the prolific Morrow Consolidated field, and more recently, within and adjacent to the Rose Run subcrop. Although these paleogeomorphic traps have yielded significant Knox production, structural and stratigraphic traps are being largely ignored. Three Knox-producing pools demonstrate structural and stratigraphic traps: the Birmingham-Erie pool in southern Erie and southwestern Lorain counties, the South Canaan pool in northern Wayne County, and the East Randolph pool in south-central Portage County. Enhanced porosity and permeability from fractures, as evident in the East Randolph pool, are also an underexplored mechanism for Knox hydrocarbon accumulation. An estimated 800 bcf of gas from undiscovered Knox resources makes the Knox one of the most attractive plays in the Appalachian basin.

  14. 33 CFR 334.855 - Salt River, Rolling Fork River, Otter Creek; U.S. Army Garrison, Fort Knox Military Reservation...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ..., Otter Creek; U.S. Army Garrison, Fort Knox Military Reservation; Fort Knox, Kentucky; danger zone. 334..., Otter Creek; U.S. Army Garrison, Fort Knox Military Reservation; Fort Knox, Kentucky; danger zone. (a.... Otter Creek from Point D (latitude 37°51′31.77″ N; longitude 86°00′03.79″ W) located approximately...

  15. 33 CFR 334.855 - Salt River, Rolling Fork River, Otter Creek; U.S. Army Garrison, Fort Knox Military Reservation...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ..., Otter Creek; U.S. Army Garrison, Fort Knox Military Reservation; Fort Knox, Kentucky; danger zone. 334..., Otter Creek; U.S. Army Garrison, Fort Knox Military Reservation; Fort Knox, Kentucky; danger zone. (a.... Otter Creek from Point D (latitude 37°51′31.77″ N; longitude 86°00′03.79″ W) located approximately...

  16. 33 CFR 334.855 - Salt River, Rolling Fork River, Otter Creek; U.S. Army Garrison, Fort Knox Military Reservation...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ..., Otter Creek; U.S. Army Garrison, Fort Knox Military Reservation; Fort Knox, Kentucky; danger zone. 334..., Otter Creek; U.S. Army Garrison, Fort Knox Military Reservation; Fort Knox, Kentucky; danger zone. (a.... Otter Creek from Point D (latitude 37°51′31.77″ N; longitude 86°00′03.79″ W) located approximately...

  17. 33 CFR 334.855 - Salt River, Rolling Fork River, Otter Creek; U.S. Army Garrison, Fort Knox Military Reservation...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ..., Otter Creek; U.S. Army Garrison, Fort Knox Military Reservation; Fort Knox, Kentucky; danger zone. 334..., Otter Creek; U.S. Army Garrison, Fort Knox Military Reservation; Fort Knox, Kentucky; danger zone. (a.... Otter Creek from Point D (latitude 37°51′31.77″ N; longitude 86°00′03.79″ W) located approximately...

  18. 33 CFR 334.855 - Salt River, Rolling Fork River, Otter Creek; U.S. Army Garrison, Fort Knox Military Reservation...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ..., Otter Creek; U.S. Army Garrison, Fort Knox Military Reservation; Fort Knox, Kentucky; danger zone. 334..., Otter Creek; U.S. Army Garrison, Fort Knox Military Reservation; Fort Knox, Kentucky; danger zone. (a.... Otter Creek from Point D (latitude 37°51′31.77″ N; longitude 86°00′03.79″ W) located approximately...

  19. Cassava (Manihot esculenta Krantz) genome harbors KNOX genes differentially expressed during storage root development.

    PubMed

    Guo, D; Li, H L; Tang, X; Peng, S Q

    2014-01-01

    In plants, homeodomain proteins play a critical role in regulating various aspects of plant growth and development. KNOX proteins are members of the homeodomain protein family. The KNOX transcription factors have been reported from Arabidopsis, rice, and other higher plants. The recent publication of the draft genome sequence of cassava (Manihot esculenta Krantz) has allowed a genome-wide search for M. esculenta KNOX (MeKNOX) transcription factors and the comparison of these positively identified proteins with their homologs in model plants. In the present study, we identified 12 MeKNOX genes in the cassava genome and grouped them into two distinct subfamilies based on their domain composition and phylogenetic analysis. Furthermore, semi-quantitative reverse transcription polymerase chain reaction analysis was performed to elucidate the expression profiles of these genes in different tissues and during various stages of root development. The analysis of MeKNOX expression profiles of indicated that 12 MeKNOX genes display differential expressions either in their transcript abundance or expression patterns. PMID:25526192

  20. Dyke-Davidoff-Masson syndrome: a clinicoradiological amalgam

    PubMed Central

    Sharma, Bhawna; Nagpal, Kadam; Handa, Rahul; Bhana, Indu

    2014-01-01

    Dyke-Davidoff-Masson syndrome is a relatively rare syndrome with its typical clinical and radiological features including facial asymmetry, hemiplegia, cerebral hemiatrophy, mental retardation with calvarial thickening, hypertrophy of sinuses and elevated petrous ridge on imaging. We present here a case of congenital type Dyke-Davidoff-Masson syndrome with some additional features in the form of microcephaly, hypospadias and pachygyria. PMID:24891488

  1. Mesoscale pervasive felsic magma migration: alternatives to dyking

    NASA Astrophysics Data System (ADS)

    Weinberg, Roberto F.

    1999-03-01

    This paper reviews the literature on dyking as a mechanism of felsic magma extraction from a source and transport to shallower crustal levels, and review the recent literature suggesting a range of alternative mechanisms of magma migration in hot crustal zones which produce mesoscale pervasive granite sheet intrusions. Recent papers have strongly favoured dyking as the main mechanism controlling magma migration. However, the initiation of dykes from a felsic magma source is fraught with difficulties, even when magma is immediately available for transportation, as in magma chambers. Within a partially molten source, magma may reside in a range of structures with a wide range of shapes, sizes and degrees of connectivity. Whereas the growth of individual dykes within a partially molten zone, and the self-propagation of large dykes into subsolidus crust, have both been studied in some detail, little attention has been given to the crucial intermediate step of the growth of a dyke network capable of producing wide crustal scale dykes. The rarity of granite dyke swarms suggests that, if dyking is the preferred mechanism of magma transport, felsic magma sources produce only few major transporting dykes during their lifetime. Alternatively, dyking is not an important mechanism. The parameters controlling the volume of the catchment drained by one such dyke, as well as other basic geometrical parameters controlling the structure of the dyke network within the source, are unknown. The ability of dyking to drain a partially molten source depends crucially on these variables and particularly on the horizontal permeability of the source. The slow velocity of viscous felsic magmas traveling in rock pores implies that magma drained during dyking is mostly that previously extracted from the pores, and resident in irregular magma bodies or dyke networks. The observation that large volumes of buoyant magma are commonly present in migmatite zones, and that dyking in these zones plays

  2. Quantifying crystal-melt segregation in dykes

    NASA Astrophysics Data System (ADS)

    Yamato, Philippe; Duretz, Thibault; May, Dave A.; Tartèse, Romain

    2015-04-01

    The dynamics of magma flow is highly affected by the presence of a crystalline load. During magma ascent, it has been demonstrated that crystal-melt segregation constitutes a viable mechanism for magmatic differentiation. However, the influences of crystal volume fraction, geometry, size and density on crystal melt segregation are still not well constrained. In order to address these issues, we performed a parametric study using 2D direct numerical simulations, which model the ascension of crystal-bearing magma in a vertical dyke. Using these models, we have characterised the amount of segregation as a function of different quantities including: the crystal fraction (φ), the density contrast between crystals and melt (Δρ), the size of the crystals (Ac) and their aspect ratio (R). Results show that crystal aspect ratio does not affect the segregation if R is small enough (long axis smaller than ~1/6 of the dyke width, Wd). Inertia within the system was also found not to influence crystal-melt segregation. The degree of segregation was however found to be highly dependent upon other parameters. Segregation is highest when Δρ and Ac are large, and lowest for large pressure gradient (Pd) and/or large values of Wd. These four parameters can be combined into a single one, the Snumber, which can be used to quantify the segregation. Based on systematic numerical modelling and dimensional analysis, we provide a first order scaling law which allows quantification of the segregation for an arbitrary Snumber and φ, encompassing a wide range of typical parameters encountered in terrestrial magmatic systems.

  3. More wells will expand knowledge of Knox group, Black Warrior basin

    USGS Publications Warehouse

    Raymond, Dorothy E.

    1991-01-01

    The Cambrian-Ordovician Knox group of the Black Warrior basin in Alabama and Mississippi has attracted the interest of the oil industry because of recent significant discoveries of oil and gas in the age-equivalent Arbuckle group carbonates of the Arkoma, Ardmore, and Anadarko basins of Oklahoma. The geologic setting of these areas is described. Oil and gas potential is assessed and the Knox production history is given. Source rock potential is outlined.

  4. Hydrocarbon potential of Cambrian-Ordovician Knox Group in south-central Kentucky

    SciTech Connect

    Gooding, P.J.

    1987-09-01

    In the eastern US, the carbonate rocks of the Cambrian-Ordovician Knox Group were deposited on a broad, gently sloping continental shelf in shallow hypersaline waters. A major unconformity occurs at the top of the Knox Group. This regional unconformity developed when the Sauk Sea retreated at the close of the Early Ordovician. In south-central Kentucky, the paleotopographic surface is characterized by extensive paleokarst developed on the upper Knox surface. The study area is located on the crest of the Cincinnati arch, a major structural feature that separates the Appalachian basin to the east from the Illinois basin on the west. Oil and gas are being produced from Cambrian-Ordovician rocks throughout the US, and south-central Kentucky is no exception. In south-central Kentucky, the Knox is of considerable economic importance. Hydrocarbon entrapment occurs at or near the unconformity at the top of the Knox. Approximately 3500 oil and gas wells and mineral exploration holes have penetrated the upper Knox Group in south-central Kentucky. Over 32 million bbl of oil have been recovered from 11 relatively shallow stratigraphic zones in 120 oil pools. These stratigraphic zones are generally encountered at depths of less than 2000 ft. A substantial amount of oil has been recovered from pools that produce exclusively from the Knox. Brecciated and fractured zones at the top of the Knox have also served as the host rock for sulfide mineralization, and these deposits may contain significant amounts of lead, zinc, and barium resources for future exploitation.

  5. The propagation and seismicity of dyke injection, new experimental evidence

    NASA Astrophysics Data System (ADS)

    Bakker, Richard R.; Fazio, Marco; Benson, Philip M.; Hess, Kai-Uwe; Dingwell, Donald B.

    2016-03-01

    To reach the surface, dykes must overcome the inherent tensile strength of the country rock. As they do, they generate swarms of seismic signals, frequently used for forecasting. In this study we pressurize and inject molten acrylic into an encapsulating host rocks of (1) Etna basalt and (2) Comiso limestone, at 30 MPa of confining pressure. Fracture was achieved at 12 MPa for Etna basalt and 7.2 MPa for Comiso limestone. The generation of radial fractures was accompanied by acoustic emissions (AE) at a dominant frequency of 600 kHz. During "magma" movement in the dykes, AE events of approximately 150 kHz dominant frequency were recorded. We interpret our data using AE location and dominant frequency analysis, concluding that the seismicity associated with magma transport in dykes peaks during initial dyke creation but remains significant as long as magma movement continues. These results have important implications for seismic monitoring of active volcanoes.

  6. Giant radiating dyke swarms on Earth and Venus

    NASA Astrophysics Data System (ADS)

    Ernst, R. E.; Head, J. W.; Parfitt, E.; Grosfils, E.; Wilson, L.

    1995-09-01

    Concentrations of dykes of basic composition emplaced in the same igneous episode or along similar trends are known as mafic dyke swarms and they occur in a wide variety of environments and over a wide range of scales on Earth. Recent radar mapping of Venus has revealed families of linear features interpreted to be the surface expression of near-surface dyke swarms. The lack of significant erosion on Venus provides a view of the surface manifestation of dyke swarm emplacement, one which complements the terrestrial perspective of erosion to deeper levels. The goal of this review is to synthesize the information available on both planets in order to use the complementary and synergistic record of mafic dyke swarm emplacement to build toward a better understanding of this important phenomenon in planetary history. We focus on the formation and evolution of giant dyke swarms which cover tens to hundreds of thousands of square kilometres on both Earth and Venus. Mafic dyke swarms on Earth occur in a wide range of modes and are observed in environments ranging from volcanic edifices (e.g., Hawaii), to central complexes (e.g., Spanish Peaks Complex, USA; Ramon Swarm, Israel), spreading centres and ophiolite complexes, compressional plate boundaries in back-arc settings (Columbia River Basalts, USA) and in continent-continent collisions. One of the most impressive modes of occurrence is that linked to the formation and evolution of mantle plumes. Terrestrial examples include a giant radiating swarm covering 100° of azimuth (the Mackenzie swarm, Canada), a 360° giant radiating swarm (the Central Atlantic reconstructed swarm), deformed giant radiating swarms (the Matachewan swarm, Canada), rift-arm associated swarms (e.g., Grenville swarm, Canada; Yakutsk swarm, Siberia), and one consisting of widely separated dykes (e.g., the Abitibi swarm, Canada). We summarize the geometric, chemical and isotopic characteristics of terrestrial dyke swarms, including their size and

  7. The conserved KNOX domain mediates specificity of tobacco KNOTTED1-type homeodomain proteins.

    PubMed Central

    Sakamoto, T; Nishimura, A; Tamaoki, M; Kuba, M; Tanaka, H; Iwahori, S; Matsuoka, M

    1999-01-01

    Overproduction of the tobacco KNOTTED1-type homeodomain proteins NTH1, NTH15, and NTH23 in transgenic tobacco plants causes mild, severe, and no morphological alterations, respectively. The deduced amino acid sequences of the homeodomains and adjacent ELK domains are highly conserved, and the N-terminal KNOX domains also are moderately conserved. To investigate the contributions of both the conserved and divergent regions to the severity of morphological alterations, we generated chimeric proteins by exchanging different regions of NTH1, NTH15, and NTH23. The severity of the abnormal phenotype was dependent upon the synergistic action of both the N terminus, containing the KNOX domain, and the C terminus, containing the ELK homeodomain. Detailed analysis focusing on the C terminus revealed that the C-terminal half of the ELK domain is more effective in inducing the abnormal phenotypes than are the homeodomains. For the N terminus, severe morphological alterations were induced by exchanging a part of the KNOX domain of NTH1 with the corresponding region of NTH15. This limited region in the KNOX domain of all homeodomain proteins includes a predicted alpha-helical region, but only that in NTH15 is predicted to form a typical amphipathic structure. We discuss the possibility, based on these results, that the secondary structure of the KNOX domain is important for the induction of abnormal morphology in transgenic tobacco plants. PMID:10449577

  8. Relationship between paleotopographic surface of Cambrian-Ordovician Knox Group and oil and gas entrapment in Kentucky

    SciTech Connect

    Gooding, P.J.

    1987-09-01

    Cambrian-Ordovician dolostones of the Knox Group constitute one of the largest occurrences of this rock type known in the US. In Kentucky, the Knox carbonate sequence attains thicknesses of more than 3500 ft. Mudstone and wackestone are dominant in the upper Knox, with lesser amounts of packstone and grainstone. The Upper Cambrian to Lower Ordovician carbonate sequences in Kentucky resulted from carbonate sedimentation on a cratonic platform in shallow, low-energy marine environments. Relative structural quiescence existed during this time. The thick sequence of shallow-water carbonates suggests that the rate of deposition generally kept pace with subsidence of the craton. Geologic environments and climatic conditions during this period were similar to those of the Bahamas today. Warm climate, sporadic rainfall, and dry trade winds probably accounted for the net loss of water by evaporation and the resulting hypersaline conditions. The paleotopographic surface that developed on top of the Knox Group is of considerable economic importance because of potential hydrocarbon entrapment at or near the unconformity. Areas where permeable and porous zones developed on the exposed Knox surface due to erosion and weathering provide reservoir conditions; also, the unconformable surface of the Knox was sealed by an overlapping impermeable formation capable of entrapping hydrocarbons. Because of pressures exerted, hydrocarbons driven by fluids or gas may migrate along the eroded Knox surface laterally and upward onto paleotopographic highs. These conditions increase the probability of finding commercial oil and gas deposits in the Cambrian-Ordovician Knox in Kentucky.

  9. Genome-wide study of KNOX regulatory network reveals brassinosteroid catabolic genes important for shoot meristem function in rice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In flowering plants, knotted1-like homeobox (KNOX) transcription factors play crucial roles in establishment and maintenance of the shoot apical meristem (SAM), from which aerial organs such as leaves, stems, and flowers initiate. We report that a rice (Oryza sativa) KNOX gene Oryza sativa homeobox1...

  10. The Role of KNOX Genes in the Evolution of Morphological Novelty in StreptocarpusW⃞

    PubMed Central

    Harrison, Jill; Möller, Michael; Langdale, Jane; Cronk, Quentin; Hudson, Andrew

    2005-01-01

    The genus Streptocarpus comprises species with diverse body plans. Caulescent species produce leaves from a conventional shoot apical meristem (SAM), whereas acaulescent species lack a conventional SAM and produce only a single leaf (the unifoliate form) or clusters of leaves from the base of more mature leaves (the rosulate form). These distinct morphologies reflect fundamental differences in the role of the SAM and the process of leaf specification. A subfamily of KNOTTED-like homeobox (KNOX) genes are known to be important in regulating meristem function and leaf development in model species with conventional morphologies. To test the involvement of KNOX genes in Streptocarpus evolution, two parologous KNOX genes (SSTM1 and SSTM2) were isolated from species with different growth forms. Their phylogenetic analysis suggested a gene duplication before the subgeneric split of Streptocarpus and resolved species relationships, supporting multiple evolutionary origins of the rosulate and unifoliate morphologies. In S. saxorum, a caulescent species with a conventional SAM, KNOX proteins were expressed in the SAM and transiently downregulated in incipient leaf primordia. The ability of acaulescent species to initiate leaves from existing leaves was found to correlate with SSTM1 expression and KNOX protein accumulation in leaves and to reflect genetic differences at two loci. Neither locus corresponded to SSTM1, suggesting that cis-acting differences in SSTM1 regulation were not responsible for evolution of the rosulate and unifoliate forms. However, the involvement of KNOX proteins in leaf formation in rosulate species suggests that they have played an indirect role in the development of morphological diversity in Streptocarpus. PMID:15659624

  11. Sedimentological cross section of Cambro-Ordovician carbonate shelf (Knox group, Conassauga Formation) in central Alabama: facies, diagenesis, potential reservoirs

    SciTech Connect

    Sternbach, L.R.

    1984-04-01

    Cambro-Ordovician thrust-imbricated carbonates in central Alabama are the focus of renewed exploration interest. Samples from east-west-trending core holes within the surface-most thrust plates reconstruct the carbonate shelf and shelf-edge facies before deformation. The Upper Cambrian shelf margin now is in the subsurface of Talledega County; coeval dolostones in the western part of the state represent the former shelf interior. Rock analogs to former environments include the following. (1) Barrier shoals (Conasauga Formation) - dark colored, partially dolomitized ooid and skeletal grainstones. (2) Submerged back-barrier and offshelf dolomitized sediments (lower Knox Group) - western belt: finely crystalline algal thrombolites, fenestral dolopelmicrites, rippled beds; eastern belt: finely laminated dolostones, slope-derived pebbles and graded beds. (3) Tidal flats (upper Knox Group) - light-colored, crystalline dolostones, dolomitized pellet grainstones, algal laminites, pseudomorphs after sulfates and early diagenetic chertification. (4) Former emergent shelf -(Knox unconformity)-pelmicrite, skeletal wackestones, erosional chert pebble conglomerate. Multiple possibilities for hydrocarbon reservoirs appear throughout the sequence. Vuggy and intercrystalline dolostone porosity is primarily in the lower Knox formations. Primary interparticle pores are retained in lower Knox algal buildups. Breccia porosity occurs in the strata below the Knox unconformity through solution of the underlying Knox Group. Fractures in the subsurface are believed to enhance permeability in all porosity types.

  12. Sedimentological cross section of Cambro-Ordovician carbonate shelf (Knox group, Conasauga Formation) in central Alabama: facies, diagenesis, potential reservoirs

    SciTech Connect

    Sternbach, L.R.

    1984-04-01

    Cambro-Ordovician thrust-imbricated carbonates in central Alabama are the focus of renewed exploration interest. Samples from east-west-trending core holes within the surface-most thrust plates reconstruct the carbonate shelf and shelf-edge facies before deformation. The Upper Cambrian shelf margin now is in the subsurface of Talledega County; coeval dolostones in the western part of the state represent the former shelf interior. Rock analogs to former environments include the following. (1) Barrier shoals (Conasauga Formation) - dark colored, partially dolomitized ooid and skeletal grainstones. (2) Submerged back-barrier and offshelf dolomitized sediments (lower Knox Group) - western belt: finely crystalline algal thrombolites, fenestral dolopelmicrites, rippled beds; eastern belt: finely laminated dolostones, slope-derived pebbles and graded beds. (3) Tidal flats (upper Knox Group) - light-colored, crystalline dolostones, dolomitized pellet grainstones, algal laminites, pseudomorphs after sulfates and early diagenetic chertification. (4) Former emergent shelf -(Knox unconformity)-pelmicrite, skeletal wackestones, erosional chert pebble conglomerate. Multiple possibilities for hydrocarbon reservoirs appear throughout the sequence. Vuggy and intercrystalline dolostone porosity is primarily in the lower Knox formations. Primary interparticle pores are retained in lower Knox algal buildups. Breccia porosity occurs in the strata below the Knox unconformity through solution of the underlying Knox Group. Fractures in the subsurface are believed to enhance permeability in all porosity types.

  13. 77 FR 66743 - Radio Broadcasting Services; Crowell, Knox City, Quanah, and Rule, TX

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-07

    ... MM Docket No. 00-148 are considered final. See Quanah, Texas, et al, 76 FR 42573, published July 19... COMMISSION 47 CFR Part 73 Radio Broadcasting Services; Crowell, Knox City, Quanah, and Rule, TX AGENCY... in 47 CFR Part 73 Radio, Radio broadcasting. Federal Communications Commission. Nazifa...

  14. Geochemical Modeling of CO2, Brine, and Reservoir Rock Interactions in the Knox Group, Western Kentucky

    NASA Astrophysics Data System (ADS)

    Zhu, J.; Parris, T. M.; Bowersox, J.; Harris, D. C.

    2011-12-01

    Regionally extensive dolostones and sandstones in the Cambrian-Ordovician Knox Group could provide commercial-scale CO2 storage capacity in the Illinois Basin of Kentucky, Illinois, and Indiana. This 1200 m thick interval of dolostone and less abundant quartz sandstone is a prospective sequestration target in the southern part of the Illinois Basin, where the Cambrian Mt. Simon Sandstone, a main sequestration target in the central part of the basin, is thin to absent, or deeply buried. The Kentucky Geological Survey (KGS) has successfully injected 690 tons of CO2 into the Knox Group through a 2477 m deep well (KGS #1 Blan well) at a test site in western Kentucky. To understand the long-term fate of CO2 stored in a saline reservoir in the Knox group, this study uses TOUGHREACT to model geochemical reactions among injected CO2, brine, and the reservoir rocks. Data collected in the KGS #1 Blan well, including rock cores, deep brine water samples, temperatures, and pressures, are the main data sources. A kinetic batch model is used first to simulate the impacts of dissolved CO2 on a mineral assemblage representing the Gunter Sandstone, a subgroup of the Knox Formation. The mineral assemblage consists of mainly quartz and dolomite with small amount of k-feldspar. The batch simulation results show precipitation of calcite, magnesite, illite, and quartz and dissolution of dolomite and k-feldspar. A 1-D radial reactive transport model is being constructed to simulate the injection test to evaluate the migration of the injected CO2, mineral dissolution and precipitation, and changes of porosity and permeability of formation rocks. The reactive model will be used to simulate hypothetical commercial scale injection scenarios to evaluate the long-term impacts of large scale CO2 injection on the Knox reservoir.

  15. Weibull-distributed dyke thickness reflects probabilistic character of host-rock strength.

    PubMed

    Krumbholz, Michael; Hieronymus, Christoph F; Burchardt, Steffi; Troll, Valentin R; Tanner, David C; Friese, Nadine

    2014-01-01

    Magmatic sheet intrusions (dykes) constitute the main form of magma transport in the Earth's crust. The size distribution of dykes is a crucial parameter that controls volcanic surface deformation and eruption rates and is required to realistically model volcano deformation for eruption forecasting. Here we present statistical analyses of 3,676 dyke thickness measurements from different tectonic settings and show that dyke thickness consistently follows the Weibull distribution. Known from materials science, power law-distributed flaws in brittle materials lead to Weibull-distributed failure stress. We therefore propose a dynamic model in which dyke thickness is determined by variable magma pressure that exploits differently sized host-rock weaknesses. The observed dyke thickness distributions are thus site-specific because rock strength, rather than magma viscosity and composition, exerts the dominant control on dyke emplacement. Fundamentally, the strength of geomaterials is scale-dependent and should be approximated by a probability distribution. PMID:24513695

  16. Weibull-distributed dyke thickness reflects probabilistic character of host-rock strength

    PubMed Central

    Krumbholz, Michael; Hieronymus, Christoph F.; Burchardt, Steffi; Troll, Valentin R.; Tanner, David C.; Friese, Nadine

    2014-01-01

    Magmatic sheet intrusions (dykes) constitute the main form of magma transport in the Earth’s crust. The size distribution of dykes is a crucial parameter that controls volcanic surface deformation and eruption rates and is required to realistically model volcano deformation for eruption forecasting. Here we present statistical analyses of 3,676 dyke thickness measurements from different tectonic settings and show that dyke thickness consistently follows the Weibull distribution. Known from materials science, power law-distributed flaws in brittle materials lead to Weibull-distributed failure stress. We therefore propose a dynamic model in which dyke thickness is determined by variable magma pressure that exploits differently sized host-rock weaknesses. The observed dyke thickness distributions are thus site-specific because rock strength, rather than magma viscosity and composition, exerts the dominant control on dyke emplacement. Fundamentally, the strength of geomaterials is scale-dependent and should be approximated by a probability distribution. PMID:24513695

  17. Dyke emplacement and propagation: a new laboratory approach

    NASA Astrophysics Data System (ADS)

    Bakker, R.; Benson, P.; Vinciguerra, S.

    2013-12-01

    It is well known that magma ascends trough the crust by the process of dyking. During dyke movement crustal rocks, specifically the volcano's basement rocks, fracture due to the stress imposed by the ascending magma, thus providing conduits for magma transport. Dykes are frequently seen in the field and have been reproduced via numerical and analogue studies. However, a number of assumptions regarding rock mechanical behavior frequently has to be made as such data are very hard to directly measure at the pressure/temperature conditions of interest: high temperatures at relatively shallow depths. Such data are key to simulating the magma intrusion dynamics through the lithologies that underlie the volcanic edifice. To bridge this gap, we have performed a suite of rock deformation experiments in both compressive and tensile regimes, using a Paterson-type triaxial apparatus on representative lithologies present in the basement of Mt. Etna. In the compressive regime, we find that sedimentary rocks present at a depth of aproximately 2 km show a B/D transition at around 300 degC and significant weakening with temperatures exceeding 400 degC. Volcanic rocks (basalt) shows a significant change in deformation behavior only at temperatures exceeding 800 degC. Such a large contrast in mechanical properties could be favorable for dyke deflection or dyke arrest. However, in the tensile regime, it remains a significant technical challenge to precisely reproduce the conditions of dyking in the lab. As a starting point, we are now testing an analogue material to replace the magma to avoid such high temperatures, relying of maintaining similar temperature/viscosity ratios between magma/country rock in the laboratory and the field. We chose PMMA (a.k.a. plexiglass) for this task as it displays a large range in viscosities (log(visc)range = 10 - 1) with temperatures between 100 and 300 degC, making it an excellent analogue material. In addition PMMA solidifies after the sample cools

  18. Geochemistry of eastern North American CAMP diabase dykes

    NASA Astrophysics Data System (ADS)

    Callegaro, S.; Marzoli, A.; Bertrand, H.; Reisberg, L. C.; Chiaradia, M.; Bellieni, G.

    2011-12-01

    The Piedmont area of the Appalachians and the coastal plains of eastern North America (ENA) were intruded between 202 and 195 Ma[1,2] by swarms of diabase (dolerite) dykes and a few sills of the Central Atlantic magmatic province (CAMP). Different trends are observed for the dykes, from NW (more frequent in the South), to N-S and NE, thus a radial pattern and a coeval emplacement driven by the bulging effect of a mantle plume were initially inferred[3]. Conversely, based on field data, an age progression can be defined from NW- to N- and NE-oriented dykes, supporting a diachronous northward rift-to-drift transition during Pangaea break-up. New geochemical data on 74 ENA dykes suggest a dominant lithospheric mantle source for these magmatic suite. A deep enriched mantle source is further discarded by the crystallization temperatures (ca.1350°C) calculated[4] for high-Fo (up to Fo89) olivines, which do not reflect very hot (i.e. mantle-plume) potential mantle temperatures. Incompatible trace element contents are fairly homogeneous and generally low, e.g. (La/Yb)Ch (0.54-2.39), typical of melts derived from a quite depleted shallow (spinel) mantle-source. However, isotopic compositions of ENA dykes display a considerable spread in initial isotopic signatures, do not show correlation with incompatible trace elements, and are independent of the orientation and age of the dykes, i.e. 87Sr/86Sr200Ma (0.7043-0.7088), ɛNd200Ma (-6.67-+2.42) and 206Pb/204Pb200Ma (17.46-18.61). Pb isotopic compositions plot above the NHRL, at positive Δ7/4 (10-17) and Δ8/4 (19-73), calling for an enriched ancient component in the mantle source. Unradiogenic 187Os/188Os200Ma ratios (0.127-0.144) argue for negligible amounts of crustal contamination and, coupled with the large range of Sr-Nd-Pb isotopic compositions, suggest generation from a strongly heterogeneous mantle source, probably metasomatized lithosphere. Lithospheric mantle underlying the Appalachian orogen may have undergone

  19. Dyke and sill injections: what mostly trigger volcano flank collapse?

    NASA Astrophysics Data System (ADS)

    Catry, Thibault; Cayol, Valérie; Michon, Laurent; Famin, Vincent; Romagnoli, Claudia; Chaput, Marie

    2010-05-01

    There is a large number of evidences that the morphostructural evolution of basaltic oceanic volcanoes (e.g. Stromboli, Hawaï and Canary Islands) results of alternating phases of growth and destruction. Among dismantling processes, flank collapses have been largely documented and interpreted as gravitational destabilization triggered by vertical injections of magma (dykes). In most cases, this interpretation has not been sustained by field observations because active volcanoes have poor occurrence of outcropped intrusions. From this point of view, Piton des Neiges volcano (La Réunion Island) represents a case in point because it has been deeply incised by erosion, providing large outcropped surfaces exhibiting the geometrical relationship between intrusions and host volcanic formations. The recent discovery of a highly deformed pile of sills at the interface between a debris avalanche deposit and a fossilized magma chamber brought to light the role of horizontal injections in the triggering of lateral collapses. The validation of this assumption rests on a digital model developed from the Mixed Boundary Element Method of elastic deformation field analysis. In this study, we modelled the intensity and the distribution of deformation and Coulomb stresses perturbation due to the injection of dykes along rift zones and a sill below the flank of a basaltic volcano. We quantified the influence of the intrusions in the mechanical state of the edifice, based on the deformation detected during an intrusion of magma at Piton de la Fournaise volcano. By comparing the deformation generated by sills to that generated by dykes, our modelling approach concludes that the area deformed by a sill injection is much wider than that deformed by a dyke injection. Moreover, we found that sill injection reaches higher intensities of lateral displacements. The combination of field data and our modelling results suggests therefore that repeated sill injection is an underestimated trigger

  20. Permanent groundwater storage in basaltic dyke fractures and termite mound viability

    NASA Astrophysics Data System (ADS)

    Mège, Daniel; Rango, Tewodros

    2010-04-01

    Many basaltic dykes of the Ethiopian flood basalt province are observed in the northwestern Ethiopian lowlands. In this area, the termites preferentially build their epigeous mounds on the top of dolerite dykes. The relationship between termite mounds and dykes is investigated from the analysis of their distribution along one of these dykes, of thickness 2-5 m, that we could follow over 2000 m. Termite mounds are periodically spaced (mean distance 63 m, R2 = 0.995), and located exclusively where the topographic relief of the dyke is not more than 2 m above the surrounding area. From these observations and from the geological context, a hydrological circuit model is proposed in which (1) dykes are preferential conduits for groundwater drainage during the rainy season due to pervasive jointing, (2) during the dry season, the portion of the dyke forming a local topographic relief area dries up more quickly than the surroundings, the elevation difference between the dyke summit and the surroundings being a factor restricting termite mound development. For dyke topographic relief >2 m, drying is an obstacle for maintaining the appropriate humidity for the termite colony life. Periodic termite mound spacing is unlikely to be related to dyke or other geological properties. It is more likely related to termite population behaviour, perhaps to clay shortage, which restricts termite population growth by limiting the quantity of building material available for mound extension, and triggers exploration for a new colonization site that will be located along the dyke at a distance from the former colony that may be controlled by the extent of the zone covered by its trail pheromones. This work brings out the importance of dykes in channelling and storing groundwater in semiarid regions, and shows that dykes can store groundwater permanently in such settings even though the dry season is half the year long. It contributes also to shedding light on water supply conditions

  1. Seismic footprints of shallow dyke propagation at Etna, Italy

    PubMed Central

    Falsaperla, Susanna; Neri, Marco

    2015-01-01

    One of the key issues in forecasting volcanic eruptions is to detect signals that can track the propagation of dykes towards the surface. Continuous monitoring of active volcanoes helps significantly in achieving this goal. The seismic data presented here are unique, as they document surface faulting processes close (tens to a few hundred meters) to their source, namely the dyke tip. They originated nearby - and under - a seismic station that was subsequently destroyed by lava flows during eruptive activity at Etna volcano, Italy, in 2013. On February 20, a ~600 m-long and ~120 m wide NW-SE fracture field opened at an altitude between 2750 and 2900 m. The consequent rock dislocation caused the station to tilt and offset the seismic signal temporarily. Data acquisition continued until the arrival of the lava flow that led to the breakdown of the transmission system. Shallow ground fracturing and repeated low-frequency oscillations occurred during two stages in which the seismic signal underwent a maximum offset ~2.57 × 104 nm/s. Bridging instrumental recordings, fieldwork and conceptual modelling, these data are interpreted as the seismic footprints of a magmatic dyke intrusion that moved at speed ~0.02 m/s (first stage) and 0.46 m/s (second stage). PMID:26173557

  2. Seismic footprints of shallow dyke propagation at Etna, Italy.

    PubMed

    Falsaperla, Susanna; Neri, Marco

    2015-01-01

    One of the key issues in forecasting volcanic eruptions is to detect signals that can track the propagation of dykes towards the surface. Continuous monitoring of active volcanoes helps significantly in achieving this goal. The seismic data presented here are unique, as they document surface faulting processes close (tens to a few hundred meters) to their source, namely the dyke tip. They originated nearby - and under - a seismic station that was subsequently destroyed by lava flows during eruptive activity at Etna volcano, Italy, in 2013. On February 20, a ~600 m-long and ~120 m wide NW-SE fracture field opened at an altitude between 2750 and 2900 m. The consequent rock dislocation caused the station to tilt and offset the seismic signal temporarily. Data acquisition continued until the arrival of the lava flow that led to the breakdown of the transmission system. Shallow ground fracturing and repeated low-frequency oscillations occurred during two stages in which the seismic signal underwent a maximum offset ~2.57 × 10(4) nm/s. Bridging instrumental recordings, fieldwork and conceptual modelling, these data are interpreted as the seismic footprints of a magmatic dyke intrusion that moved at speed ~0.02 m/s (first stage) and 0.46 m/s (second stage). PMID:26173557

  3. Dyke emplacement at the incipient Namibian margin - structural and anisotropy of magnetic susceptibility (AMS) studies in the Henties Bay - Outjo Dyke Swarm

    NASA Astrophysics Data System (ADS)

    Wiegand, Miriam; Trumbull, Robert; Greiling, Reinhard O.

    2010-05-01

    During the Cretaceous breakup of western Gondwana, the conjugate Namibian and South American margins were the site of flood basalts, mafic dyke swarms and subvolcanic intrusive complexes which make up the South Atlantic Large Igneous Province and the volcanic margin of northwestern Namibia. This contribution presents data on internal fabrics in mafic dykes (mostly subalkaline tholeiitic dolerites) from the major Henties Bay-Outjo dyke swarm (HOD) in coastal and inland NW Namibia, which are discussed in terms of magma emplacement. The HOD is some 100 km wide and extends at least 500 km from the continental margin. The dykes were emplaced in Neoproterozoic (Panafrican) Damara mobile belt, which is bounded by the Angola/Congo craton on the north and the Kalahari craton on the south. Field relations and radiometric dates indicate Early Cretaceous emplacement ages for the dykes. In coastal exposures north of the HOD, dolerite dykes are mainly coast-parallel (NNW-SSE) and syn-tectonic with normal faults that offset Etendeka lavas. Coast-parallel dykes are also common within the HOD, but the great majority of dykes strike NE-SW. We observed the latter dykes to crosscut coast-parallel ones. But the opposite relationship is also found locally. The dominant NE-SW strike of HOD indicates the influence of the Damara Belt structural grain at a regional scale, but locally the dykes commonly crosscut basement foliations and lithologic contacts. Depending on dyke thickness, which varies in the HOD from a few cm to about 50 m), the dykes are variably fine grained with chilled margins. Vesiculation is seldom observed. Typical textures are intersertal to subophitic, with plagioclase, clinopyroxene and olivine being the main mineral phases. Common minor minerals include opaque oxides and acicular apatite. Linear dykes are composed of segments, 10 m to some km in length, which are connected by transfer zones. Often a minor horizontal displacement can be observed between these segments

  4. Pre-Alleghenian (Pennsylvanian-Permian) hydrocarbon emplacement along Ordovician Knox unconformity, eastern Tennessee

    SciTech Connect

    Haynes, F.M.; Kesler, S.E.

    1989-03-01

    Cores taken during exploration for Mississippi Valley-type lead and zinc ores in the Mascot-Jefferson City zinc district of eastern Tennessee commonly contain hydrocarbon residues in carbonate rocks of the Knox Group immediately below the Lower Ordovician Knox unconformity. The location and number of these residue-bearing strata reveal information about the Paleozoic history of hydrocarbon emplacement in the region. Contour maps, generated from nearly 800 holes covering more than 20 km/sup 2/, indicate that zones with elevated organic content in the uppermost 30 m of the Lower Ordovician Mascot Dolomite show a strong spatial correlation with Middle Ordovician paleotopographic highs. These same zones show no spatial association with present-day structural highs, which were formed during Pennsylvanian-Permian Alleghenian tectonism. This suggests that the physical entrapment of hydrocarbons migrating through the upper permeable units of the Mascot must have occurred prior to the principal tectonism of the Alleghenian orogeny. 7 figures, 1 table.

  5. Ring the BELL and tie the KNOX: roles for TALEs in gynoecium development

    PubMed Central

    Arnaud, Nicolas; Pautot, Véronique

    2014-01-01

    Carpels are leaf-like structures that bear ovules, and thus play a crucial role in the plant life cycle. In angiosperms, carpels are the last organs produced by the floral meristem and they differentiate a specialized meristematic tissue from which ovules develop. Members of the three-amino-acid-loop-extension (TALE) class of homeoproteins constitute major regulators of meristematic activity. This family contains KNOTTED-like (KNOX) and BEL1-like (BLH or BELL) homeodomain proteins, which function as heterodimers. KNOX proteins can have different BELL partners, leading to multiple combinations with distinct activities, and thus regulate many aspects of plant morphogenesis, including gynoecium development. TALE proteins act primarily through direct regulation of hormonal pathways and key transcriptional regulators. This review focuses on the contribution of TALE proteins to gynoecium development and connects TALE transcription factors to carpel gene regulatory networks. PMID:24688486

  6. Giant radiating dyke swarms on Earth and Venus

    NASA Technical Reports Server (NTRS)

    Ernst, Richard E.; Head, James W.; Parfitt, Elisabeth; Wilson, Lionel; Grosfils, Eric

    1993-01-01

    On Earth, giant radiating dyke swarms are usually preserved as fan-shaped fragments which have been dismembered from their original configuration by subsequent plate tectonic rifting events. Analysis of the largest fragments and consideration of their original configuration has led to the idea that many swarms are plume related, and that dyke swarms radiate away from plume centers. Magellan radar data reveal abundant intact giant radiating swarms on Venus which are similar in scale and pattern to those on Earth. The absence of intense weathering and plate tectonic processes on Venus accounts for the preservation of the primary radiating patterns. It is characteristic of both Earth and Venus that giant radiating dikes are emplaced laterally for distances of at least 2000 km away from plume centers. At distances beyond the influence of the plume on both Earth and Venus, the radiating dyke pattern is often swept into a linear pattern aligned with the regional stress field. There is tremendous potential synergism between the characterization and analysis of terrestrial dyke swarms (where significant erosion has revealed their structure and emplacement directions at depth) and the giant swarms of Venus (where the complete circumferential structure is preserved, and the surface fracture systems above near surface dikes and the nature of the central source regions are revealed). In this study, we report on the characteristics of radial dyke swarms on Earth and Venus and draw some preliminary comparisons from the two perspectives. In summary, on both planets there is evidence for plume-related magmatic centers associated with vertical and lateral injection of magma over considerable distances (up to at least 2000 km). The abundance of very broadly radiating swarms on Venus supports the notion that the swarms on Earth were radiating over broad sectors at the time of intrusion but were dissected by later events. The Venus data show that a swarm can change from radiating

  7. Analysis and implications of the miscarriages of justice of Amanda Knox and Raffaele Sollecito.

    PubMed

    Gill, Peter

    2016-07-01

    The case of the 'murder of Meredith Kercher' has been the subject of intense media scrutiny since 2007 when the offence was committed. Three individuals were arrested and accused of the crime. Amanda Knox and Raffaele Sollecito were exonerated in March 2015. Another defendant, Rudy Guede, remains convicted as the sole perpetrator. He was implicated by multiple DNA profiles recovered from the murder room and the bathroom. However, the evidence against Guede contrasted strongly with the limited evidence against two co-defendants, Amanda Knox and Raffaele Sollecito. There were no DNA profiles pertaining to Amanda Knox in the murder room itself. She was separately implicated by a knife recovered remote from the crime scene (discovered in a cutlery drawer at Sollecito's apartment), along with DNA profiles in a bathroom that she had shared with the victim. Upon analysis a low level trace of DNA attributed to the murder victim was found on the blade of a knife, along with DNA profiles attributed to Amanda Knox from the handle. However, there was no evidence of blood on the knife blade itself. A separate key piece of evidence was a DNA profile attributed to Raffaele Sollecito recovered from a forcibly removed bra-clasp found in the murder room. There followed an extraordinary series of trials and retrials where the pair were convicted, exonerated, re-convicted and finally, in March 2015 they were finally exonerated (no further appeal is possible). Since Knox and Sollecito have been found innocent it is opportune to carry out an extensive review of the case to discover the errors that led to conviction so that similar mistakes do not occur in the future. It is accepted that the DNA profiles attributed to them were transferred by methods unrelated to the crime event itself. There is a wealth of material available from the judgements and other reports which can be analysed in order to show the errors of thinking. The final judgement of the case-the Marasca-Bruno motivation

  8. Geological consequences of the Saemangeum Dyke, mid-west coast of korea: A review

    NASA Astrophysics Data System (ADS)

    Lee, Hee Jun; Lee, Soo Hwan

    2012-12-01

    The Saemangeum Dyke is located in an estuarine setting, regulated in a complicated manner by a macrotidal regime, rivers, and winter monsoon. Accordingly, the constructed dyke resulted in a variety of artificial changes in geological characteristics in the estuary and its vicinity. To investigate those dyke-induced changes, the KORDI (Korea Ocean Research and Development Institute) performed sedimentological and sediment-dynamical observations from 2002 to 2010. On the basis of the KORDI results, the major geological changes and associated dynamical processes are reviewed. Five phenomena, among others, are focused on: depositional-channel creation; gap-related erosion; forced movements of surface sands; tidal-flat growth inside the dyke; and blanketing of mud over the sandy seafloor. These phenomena were unforeseen before the dyke construction, and reflect that the dyke could cause both erosion and deposition on an estuarine scale. The investigations conclude that the sediments in the dyke-influenced region were derived from the two rivers, Mangyeong and Dongjin, of the estuary. This is completely contrary to the offshore origin proposed before the dyke construction. As a result, the review supports the proposal that a thorough geological investigation and rational forecast is necessary prior to dyke construction to avoid economic loss and a fractious environmental debate.

  9. Geologic characterization and carbon storage resource estimates for the knox group, Illinois Basin, Illinois, Indiana and Kentucky

    SciTech Connect

    Harris, David; Ellett, Kevin; Rupp, John; Leetaru, Hannes

    2014-09-30

    Research documented in this report includes (1) refinement and standardization of regional stratigraphy across the 3-state study area in Illinois, Indiana, and Kentucky, (2) detailed core description and sedimentological interpretion of Knox cores from five wells in western Kentucky, and (3) a detailed calculation of carbon storage volumetrics for the Knox using three different methodologies. Seven regional cross sections document Knox formation distribution and thickness. Uniform stratigraphic nomenclature for all three states helps to resolve state-to-state differences that previously made it difficult to evaluate the Knox on a basin-wide scale. Correlations have also refined the interpretation of an important sandstone reservoir interval in southern Indiana and western Kentucky. This sandstone, a CO2 injection zone in the KGS 1 Blan well, is correlated with the New Richmond Sandstone of Illinois. This sandstone is over 350 ft (107 m) thick in parts of southern Indiana. It has excellent porosity and permeability at sufficient depths, and provides an additional sequestration target in the Knox. The New Richmond sandstone interval has higher predictability than vuggy and fractured carbonates, and will be easier to model and monitor CO2 movement after injection.

  10. Dyke Monitorin by the Means of Persistent Scattering Interferometry at the Coast of Northern Germany

    NASA Astrophysics Data System (ADS)

    Seidel, M.; Marzahn, P.; Ludwig, R.

    2016-06-01

    40 percent of the world's population are presently living in coastal areas or along the main rivers. Taking into account that the vulnerability of these areas is increasing due to sea-level rise and coastal hazards such as storm surges or extreme rainfall events accompanied with floods, the importance of safety structures such as dykes is increasing as well. Hence, a spatial distributed dyke monitoring should be part of a sustainable adaptation strategy. Due to increasing amount of SAR-data from various satellites with high spatial and temporal coverage, the means of SAR-interferometry could be an essential tool to ensure this kind of required monitoring. Given this prospect, Persistent Scattering Interferometry (PSI) will be a very suitable monitoring technique for dyke structures to identify dyke movement with the accuracy of few millimetres. This procedure focuses on pixels that show a stable scattering behaviour in a sequence of multiple SAR-scenes. In opposition to ground-measurements, the spatial coverage of this technique provides comparable results for different parts of the dyke; furthermore weak segments with particular high movements could be identified in advance. This could prevent future dyke crevasses and help to reduce risks in high-populated areas. This paper attempts to describe the potential of the PSI technique for a spatial distributed dyke monitoring at the coast in northern Germany. 21 ERS-2 scenes and 16 Envisat ASAR scenes were analysed. Those Scenes cover an area of a sea shore dyke including a flood regulation barrage and results point out the potential for this technique to monitor dyke structures. Even though the observed dyke doesn't show any significant deformation rates, the two datasets show the same signal for the whole dyke.

  11. Fault-related carbonate breccia dykes in the La Chilca area, Eastern Precordillera, San Juan, Argentina

    NASA Astrophysics Data System (ADS)

    Castro de Machuca, Brígida; Perucca, Laura P.

    2015-03-01

    Carbonate fault breccia dykes in the Cerro La Chilca area, Eastern Precordillera, west-central Argentina, provide clues on the probable mechanism of both fault movement and dyke injection. Breccia dykes intrude Upper Carboniferous sedimentary rocks and Triassic La Flecha Trachyte Formation. The timing of breccia dyke emplacement is constrained by cross cutting relationships with the uppermost Triassic unit and conformable contacts with the Early Miocene sedimentary rocks. This study supports a tectonic-hydrothermal origin for these breccia dykes; fragmentation and subsequent hydraulic injection of fluidized breccia are the more important processes in the breccia dyke development. Brecciation can be triggered by seismic activity which acts as a catalyst. The escape of fluidized material can be attributed to hydrostatic pressure and the direction of movement of the material establishes the direction of least pressure. Previous studies have shown that cross-strike structures have had an important role in the evolution of this Andean segment since at least Triassic times. These structures represent pre-existing crustal fabrics that could have controlled the emplacement of the dykes. The dykes, which are composed mostly of carbonate fault breccia, were injected upward along WNW fractures.

  12. Mapping Van

    NASA Technical Reports Server (NTRS)

    1994-01-01

    A NASA Center for the Commercial Development of Space (CCDS) - developed system for satellite mapping has been commercialized for the first time. Global Visions, Inc. maps an area while driving along a road in a sophisticated mapping van equipped with satellite signal receivers, video cameras and computer systems for collecting and storing mapping data. Data is fed into a computerized geographic information system (GIS). The resulting amps can be used for tax assessment purposes, emergency dispatch vehicles and fleet delivery companies as well as other applications.

  13. The Aiguablava dyke swarm: emplacement and paleostress in a fractured basement

    NASA Astrophysics Data System (ADS)

    Martínez-Poza, Ana Isabel; Druguet, Elena; Castaño, Lina Marcela; Carreras, Jordi

    2013-04-01

    A structural analysis has been performed in the Upper Permian lamprophyric dyke swarm of Aiguablava (NE Spain). Dyke emplacement is related to the presence of a widespread joint network, likely developed during the cooling and decompression of the late Variscan granitic host rocks. In order to characterize the patterns of both the joint system and the dyke swarm, a trend frequency analysis has been performed using the circular scanlines method (Mauldon et al., 2001). The sub-vertical joint pattern consists on two major orthogonal sets at ≈N23°, ≈N113° and secondary sets at ≈N0° and ≈N90°, among others. These four fracture sets are interpreted as previous to the lamprophyre intrusion event, because they are either exploited or cross-cut by the lamprophyres. The subvertical dykes have a mean N113° trend, which corresponds to the trend of one of the main joint sets. Despite this overall orientation of dykes, segmentation is a noticeable feature at the Dm- to cm-scale, and this is probably related to the localized dyke intrusion into the other pre-existing secondary joint sets. Dyke opening directions has been measured from matching dyke jogs or markers in the host rock, with a mean orientation of 021/04. A three-dimensional paleostress analysis has been carried out from dyke orientations, applying the Mohr circle construction of Jolly and Sanderson (1997), and the parameters R' (driving pressure ratio, R'= 0.156) and φ (stress ratio, φ = 0.45) were calculated. From this analysis, we have obtained a sub-vertical maximum (σ1) and a NNE-SSW minimum (σ3) stress axes, consistent with the sub-horizontal mean trend of dyke opening measured in the field. It is inferred that many of the pre-existing joint sets were exploited by magmatic dykes, being the ≈N113° joint set (normal to σ3) the most favourable for dyke emplacement. At that time, magmatic pressure related to dyke intrusion, Pm, was lower than the intermediate principal stress axis, σ2 . Our

  14. Microstructural indicators of convection in sills and dykes

    NASA Astrophysics Data System (ADS)

    Holness, Marian; Neufeld, Jerome; Gilbert, Andrew

    2016-04-01

    . In mafic sills, the average apparent aspect ratio (AR), as measured in thin-section, varies smoothly with model crystallization times (calculated assuming diffusive heat loss), consistent with in situ growth in solidification fronts. However, AR is invariant across individual mafic dykes, with decreasing values (i.e. more blocky grains) as the dyke width increases. This difference can be accounted for by the plagioclase in dykes growing as individual grains and clusters suspended in a convecting magma. Cooling at a vertical wall, as is the case for dykes, will always result in a gravitational convective instability, and therefore crystal-poor magma in dykes will always convect. As solidification proceeds, the increasing volume fraction of suspended crystals will eventually damp convection: the final stages of solidification occur in static crystal-rich magma, containing a well-mixed grain population. That the Shiant Isles Main Sill exhibits evidence for prolonged convection of sufficient vigour to suspend 5 mm olivine clusters, while other sills of comparable thickness contain plagioclase with grain shapes indicative of growth predominantly in solidification fronts, is most likely due to the composite nature of the Shiant. The 140m unit is underlain by 23m of picrite which intruded shortly before - this heat source would have acted as a strong driver for convection.

  15. GEOCHEMICAL INVESTIGATIONS OF CO₂-BRINE-ROCK INTERACTIONS OF THE KNOX GROUP IN THE ILLINOIS BASIN

    SciTech Connect

    Yoksoulian, Lois; Berger, Peter; Freiburg, Jared; Butler, Shane; Leetaru, Hannes

    2014-09-30

    Increased output of greenhouse gases, particularly carbon dioxide (CO₂), into the atmosphere from anthropogenic sources is of great concern. A potential technology to reduce CO₂ emissions is geologic carbon sequestration. This technology is currently being evaluated in the United States and throughout the world. The geology of the Illinois Basin exhibits outstanding potential as a carbon sequestration target, as demonstrated by the ongoing Illinois Basin – Decatur Project that is using the Mt. Simon Sandstone reservoir and Eau Claire Shale seal system to store and contain 1 million tonnes of CO₂. The Knox Group-Maquoketa Shale reservoir and seal system, located stratigraphically above the Mt. Simon Sandstone-Eau Claire Shale reservoir and seal system, has little economic value as a resource for fossil fuels or as a potable water source, making it ideal as a potential carbon sequestration target. In order for a reservoir-seal system to be effective, it must be able to contain the injected CO₂ without the potential for the release of harmful contaminants liberated by the reaction between CO₂-formation fluids and reservoir and seal rocks. This study examines portions of the Knox Group (Potosi Dolomite, Gunter Sandstone, New Richmond Sandstone) and St. Peter Sandstone, and Maquoketa Shale from various locations around the Illinois Basin. A total of 14 rock and fluid samples were exposed to simulated sequestration conditions (9101–9860 kPa [1320–1430 psi] and 32°–42°C [90°– 108°F]) for varying amounts of time (6 hours to 4 months). Knox Group reservoir rocks exhibited dissolution of dolomite in the presence of CO₂ as indicated by petrographic examination, X-ray diffraction analysis, and fluid chemistry analysis. These reactions equilibrated rapidly, and geochemical modeling confirmed that these reactions reached equilibrium within the time frames of the experiments. Pre-reaction sample mineralogy and postreaction fluid geochemistry from this

  16. Modeling Interventions in the Owned Cat Population to Decrease Numbers, Knox County, TN.

    PubMed

    Lancaster, Evan P; Lenhart, Suzanne; Ojogbo, Ejebagom J; Rekant, Steven I; Scott, Janelle R; Weimer, Heidi; New, John C

    2016-01-01

    To find management strategies for controlling the owned cat population in Knox County, TN, the authors formulated a mathematical model using biological properties of such nonhuman animals and spay actions on certain age classes. They constructed this discrete-time model to predict the future owned cat population in this county and to evaluate intervention strategies to surgically sterilize some proportion of the population. Using the predicted population size and the number of surgeries for specific scenarios, they showed that focusing on specific age classes can be an effective feature in spay programs. PMID:27152694

  17. The application aeromagnetic data for dyke swarm mapping (an example the Ladoga region, Russia)

    NASA Astrophysics Data System (ADS)

    Vasilieva, T.; Frank-Kamenetsky, D.

    2003-04-01

    Vasilieva T.I., Frank-Kamenetsky D.A., Zayonchek A.V. The main factor of the Fennoscandian evolution in Late Proterozoic was inter- and intracratonic rifting. However, products of magmatic activity were removed by erosion. Thus, only plutonic bodies and dyke swarms allow us to reconstruct the Fennoscandian shield tectono-magmatic evolution in Late Proterozoic. The rifting processes in southeastern Fennoscandia took place in Riphean. The earlier are several massifs of rapakivi-granite accompanied by mafic dyke swarms with age about 1.64 to 1.51 Ga were formed. The Middle Riphean is characterized by rift structure forming. They are known in Russia (White Sea rift system, northern Kola, Ladoga Lake, probably, Onega Lake), Finland (Muhos, Satakunta) and central Sweden. The age of mafic magmatic complexes, corresponding with these rift systems, is 1.24 Ga (Suominen, 1991). There are at least two stages of Riphean evolution and magmatic complexes in Ladoga Lake region. They are the Salminski and Vyborg rapakivi-granites at first, Salminski volcano-sedimentary suite, Valaam sill, Hopunvaara intrusion and several dolerites dykes at second. Our detailed studies based on magnetic geophysical data. A combination of geophysical methods and GIS provided effective mapping of dyke swarms in NW Ladoga. It has shown that the Fe-enriched olivine dolerite dykes, it was described on the NW coast of Ladoga Lake, are very locally developed forming narrow zone, which runs through Sortavala town and several islands. The dykes were clearly observed, because of their extremely high magnetic susceptibility. The dykes strike toward NW corresponding to the longest axis of the graben. Chemical identity of the dykes and Salminski lavas allows considering the age of this rifting about 1.35 Ga. The other dyke complexes were being described in North-West Ladoga region. It is dykes of fresh clinopyroxene dolerites. Probably, the dykes are accompanying by rapakivi-granites. Unfortunately, very

  18. Segmented lateral dyke growth in a rifting event at Bárðarbunga volcanic system, Iceland.

    PubMed

    Sigmundsson, Freysteinn; Hooper, Andrew; Hreinsdóttir, Sigrún; Vogfjörd, Kristín S; Ófeigsson, Benedikt G; Heimisson, Elías Rafn; Dumont, Stéphanie; Parks, Michelle; Spaans, Karsten; Gudmundsson, Gunnar B; Drouin, Vincent; Árnadóttir, Thóra; Jónsdóttir, Kristín; Gudmundsson, Magnús T; Högnadóttir, Thórdís; Fridriksdóttir, Hildur María; Hensch, Martin; Einarsson, Páll; Magnússon, Eyjólfur; Samsonov, Sergey; Brandsdóttir, Bryndís; White, Robert S; Ágústsdóttir, Thorbjörg; Greenfield, Tim; Green, Robert G; Hjartardóttir, Ásta Rut; Pedersen, Rikke; Bennett, Richard A; Geirsson, Halldór; La Femina, Peter C; Björnsson, Helgi; Pálsson, Finnur; Sturkell, Erik; Bean, Christopher J; Möllhoff, Martin; Braiden, Aoife K; Eibl, Eva P S

    2015-01-01

    Crust at many divergent plate boundaries forms primarily by the injection of vertical sheet-like dykes, some tens of kilometres long. Previous models of rifting events indicate either lateral dyke growth away from a feeding source, with propagation rates decreasing as the dyke lengthens, or magma flowing vertically into dykes from an underlying source, with the role of topography on the evolution of lateral dykes not clear. Here we show how a recent segmented dyke intrusion in the Bárðarbunga volcanic system grew laterally for more than 45 kilometres at a variable rate, with topography influencing the direction of propagation. Barriers at the ends of each segment were overcome by the build-up of pressure in the dyke end; then a new segment formed and dyke lengthening temporarily peaked. The dyke evolution, which occurred primarily over 14 days, was revealed by propagating seismicity, ground deformation mapped by Global Positioning System (GPS), interferometric analysis of satellite radar images (InSAR), and graben formation. The strike of the dyke segments varies from an initially radial direction away from the Bárðarbunga caldera, towards alignment with that expected from regional stress at the distal end. A model minimizing the combined strain and gravitational potential energy explains the propagation path. Dyke opening and seismicity focused at the most distal segment at any given time, and were simultaneous with magma source deflation and slow collapse at the Bárðarbunga caldera, accompanied by a series of magnitude M > 5 earthquakes. Dyke growth was slowed down by an effusive fissure eruption near the end of the dyke. Lateral dyke growth with segment barrier breaking by pressure build-up in the dyke distal end explains how focused upwelling of magma under central volcanoes is effectively redistributed over long distances to create new upper crust at divergent plate boundaries. PMID:25517098

  19. ANALYSIS OF FAULT SEAL POTENTIAL FOR KNOX RESERVOIRS IN THE SOUTHERN ILLINOIS BASIN

    SciTech Connect

    Hickman, John; Leetaru, Hannes

    2014-09-30

    The presence of known faults near potential geologic CO2 sequestration sites significantly raises the uncertainty of having a sufficient seal to prevent leakage along the fault plane from the intended reservoir. In regions where relocating a large sequestration project a considerable distance away from any known faults is impractical, a detailed analysis of the sealing potential of any faults within the projected future injection plume must be performed. In order to estimate the sealing potential of faults within the Late Cambrian-Early Ordovician Knox Supergroup in the Illinois Basin, two well-based cross sections were produced across two different regional fault systems (Rough Creek Fault Zone in Kentucky, and the unnamed core fault of the LaSalle Anticlinorium in Illinois) to calculate subsurface stratigraphic juxtapositions across each fault zone. Using this stratigraphic and lithologic data, three different algorithms were used to calculate the sealing potential of a theoretical Knox reservoir at each section location. These results indicate a high probability for sealing within the Rough Creek Fault Zone, but a much lower probability for a continuous seal within the LaSalle Anticlinorium.

  20. Refractory Seizure in Childhood: Dyke-Davidoff-Masson Syndrome Revisited.

    PubMed

    Dutta, Abhijit; Bose, Sagar; Sen, Kaushik; Pandit, Narayan; Sharma, Samarth

    2016-07-01

    Dyke-Davidoff-Masson syndrome (DDMS) is a rare disorder characterized by recurrent seizures, facial asymmetry, contralateral hemiplegia, radiologic features of cerebral hemiatrophy, and ipsilateral compensatory hypertrophy of the skull bone and sinuses. We describe three cases of children with DDMS, who initially presented with refractory seizure to the pediatric department of North Bengal Medical College and Hospital, India. In each case, the clinical features noted along with computed tomography or magnetic resonance imaging helped confirm the diagnosis of DDMS. DDMS should be considered as a differential diagnosis of refractory seizures in children. We seek to emphasize the importance of thorough clinical and neuroimaging workup of seizure disorder in children for the proper management of the condition. PMID:27403244

  1. Refractory Seizure in Childhood: Dyke-Davidoff-Masson Syndrome Revisited

    PubMed Central

    Dutta, Abhijit; Bose, Sagar; Sen, Kaushik; Pandit, Narayan; Sharma, Samarth

    2016-01-01

    Dyke-Davidoff-Masson syndrome (DDMS) is a rare disorder characterized by recurrent seizures, facial asymmetry, contralateral hemiplegia, radiologic features of cerebral hemiatrophy, and ipsilateral compensatory hypertrophy of the skull bone and sinuses. We describe three cases of children with DDMS, who initially presented with refractory seizure to the pediatric department of North Bengal Medical College and Hospital, India. In each case, the clinical features noted along with computed tomography or magnetic resonance imaging helped confirm the diagnosis of DDMS. DDMS should be considered as a differential diagnosis of refractory seizures in children. We seek to emphasize the importance of thorough clinical and neuroimaging workup of seizure disorder in children for the proper management of the condition. PMID:27403244

  2. Geochemistry of the Palitana flood basalt sequence and the Eastern Saurashtra dykes, Deccan Traps: clues to petrogenesis, dyke-flow relationships, and regional lava stratigraphy

    NASA Astrophysics Data System (ADS)

    Sheth, Hetu C.; Zellmer, Georg F.; Kshirsagar, Pooja V.; Cucciniello, Ciro

    2013-04-01

    Recent studies of large mafic dyke swarms in the Deccan Traps flood basalt province, India, indicate that some of the correlative lava flows reached several hundred kilometers in length. Here we present field, petrographic, mineral chemical, and whole-rock geochemical (including Sr-Nd isotopic) data on the Palitana lava sequence and nearby dykes in the Saurashtra region of the northwestern Deccan Traps. These rocks are moderately evolved, many with low-Ti-Nb characteristics. We infer that most dykes are notably (and systematically) less contaminated by ancient continental crust than the Palitana flows, but four dykes are equally or significantly more contaminated, with some of the most extreme Sr-Nd isotopic compositions seen in the entire Deccan Traps (initial ɛNd is as low as -18.0). A Bhimashankar-type and a Poladpur-type dyke are present several hundred kilometers from the type section of these magma types in the Western Ghats escarpment. We find no geochemical correlations between the Palitana sequence and three subsurface sequences in NE Saurashtra containing abundant picritic rocks, surface lavas previously studied from Saurashtra, or the Western Ghats sequence. Intriguingly, the Eastern Saurashtra dykes cannot have been feeders to any of these lava sequences. Feeder dykes of these sequences may be located in southwestern or central Saurashtra, or in the Dhule-Nandurbar-Dediapada areas across the Gulf of Cambay, 200-300 km east of Palitana. Our results indicate polycentric flood basalt eruptions not only on the scale of the Deccan Traps province, but also within the Saurashtra region itself.

  3. Detailled AMS analysis of recent dykes. Inferences about the flow regime and progression magnetic trends.

    NASA Astrophysics Data System (ADS)

    Pueyo Anchuela, Ó.; Gil Imaz, A.; Lago Sanjosé, M.; França, Z.; Forjaz, V. H.

    2009-04-01

    Anisotropy of Magnetic Susceptibility (AMS) has been applied to characterize the flow and emplacement conditions in tabular intrusions. The results in dykes have shown different models of relationship between the AMS ellipsoids and rock-fabric. These models include: a) imbrications during the flow observed in the margins of the intrusion (in the proximity of the dyke walls), b) magnetic lineation parallel to the flow, c) magnetic lineation normal to the flow (rolling of particles) or d) not evident relations between the flow and the magnetic axis. This complexity makes that, even when no mineralogical complexities exist, a contrast with outcrop evidences, shear indicators, orientation of grain, bubbles or vacuoles are needed. This complexity can be increased when this methodology is applied to old dykes, where not only the flow has influenced the AMS. In cases where the emplacement is syn-tectonic, or where deformational processes after the emplacement exist, the relation between flow regime and AMS can be more complex. To understand the changes and the model of emplacement in dykes, 12 recent dykes in sub-vertical position have been chosen to analyze the changes in orientation and the magnetic parameters along profiles border-center-border. The usual methodology recommends the sampling preferentially in the margin of the dykes. In this sense, the sampling has been focused in the margins but sampling also the whole extension. The average of cores for dyke is 54 (98 samples). The emplacement conditions of these dykes are related with a fracturation net parallel to the MAR in a passive manner. The dykes come from the Corvo and Flores islands, situated over North American Plate in the Western Azores (Portugal). Ten of the sampled dykes show clusters of axes and not significant variations in orientation of the magnetic ellipsoid between the sampling along the cross-sections border-center-border and the samples from both sides. Only two of the sampled dykes show

  4. Dyke Propagation Through a Partially Submerged Volcanic Edifice

    NASA Astrophysics Data System (ADS)

    Tait, S.; Taisne, B.; Limare, A.; Manga, M.; Pasquet, E.

    2014-12-01

    We have studied using analogue experiments the ascent of magma through a volcanic edifice. The edifice is simulated using a cone of gelatine and the magma is an aqueous solution. The latter is injected at the base of the cone and propagates through the edifice in hydraulic fractures that represent dykes. The buoyancy of the magma with respect to the edifice is varied by adjusting salt concentration in the aqueous solution and/or sugar concentration in the gelatine. The system is axisymmetric. After the gelatin is released from its mold, it is partially submerged in a layer of water that represents the surrounding ocean. Because the gelatin is denser than water, its weight generates an axisymmetric stress field in the edifice whose amplitude depends, for a given edifice density, on the depth of the water which represents ''sea-level''. We derive the geometry and amplitude of this stress field by using birefringence in the gelatin that results from its photoelasticity. We document the geometry of the dykes as they propagate and the elevation of eruptive fissures on the edifice as a function of the dimensionless parameters governing the system. Positive buoyancy of the magma tends to favour summit eruptions and increasing weight of the edifice (lower sea-level with respect to edifice height) tends to favour flank eruptions. We compare the experimental results with a dataset from Piton de la Fournaise, Reunion Island and draw some general conclusions about expected changes in eruptive behaviour as a volcanic island grows to greater and greater altitude above sea-level.

  5. Analysis of TALE superclass homeobox genes (MEIS, PBC, KNOX, Iroquois, TGIF) reveals a novel domain conserved between plants and animals.

    PubMed Central

    Bürglin, T R

    1997-01-01

    A new Caenorhabditis elegans homeobox gene, ceh-25, is described that belongs to the TALE superclass of atypical homeodomains, which are characterized by three extra residues between helix 1 and helix 2. ORF and PCR analysis revealed a novel type of alternative splicing within the homeobox. The alternative splicing occurs such that two different homeodomains can be generated, which differ in their first 25 amino acids. ceh-25 is an orthologue of the vertebrate Meis genes and it shares a new conserved domain of 130 amino acids with them. A thorough analysis of all TALE homeobox genes was performed and a new classification is presented. Four TALE classes are identified in animals: PBC, MEIS, TGIF and IRO (Iroquois); two types in fungi: the mating type genes (M-ATYP) and the CUP genes; and two types in plants: KNOX and BEL. The IRO class has a new conserved motif downstream of the homeodomain. For the KNOX class, a conserved domain, the KNOX domain, was defined upstream of the homeodomain. Comparison of the KNOX domain and the MEIS domain shows significant sequence similarity revealing the existence of an archetypal group of homeobox genes that encode two associated conserved domains. Thus TALE homeobox genes were already present in the common ancestor of plants, fungi and animals and represent a branch distinct from the typical homeobox genes. PMID:9336443

  6. EPA VAN OPERATIONAL MANUAL

    EPA Science Inventory

    The manual generally describes the EPA Van, and discusses both its energy control system and Van operation. The manual includes instructions for the Van's transportation, setup, safety, troubleshooting, and maintenance. The Van is a mobile research unit, designed for testing in v...

  7. Volcaniclastic dykes tell on fracturing, explosive eruption and lateral collapse at Stromboli volcano (Italy)

    NASA Astrophysics Data System (ADS)

    Vezzoli, Luigina; Corazzato, Claudia

    2016-05-01

    In the upper part of the Stromboli volcano, in the Le Croci and Bastimento areas, two dyke-like bodies of volcanic breccia up to two-metre thick crosscut and intrude the products of Vancori and Neostromboli volcanoes. We describe the lithofacies association of these unusual volcaniclastic dykes, interpret the setting of dyke-forming fractures and the emplacement mechanism of internal deposits, and discuss their probable relationships with the explosive eruption and major lateral collapse events that occurred at the end of the Neostromboli period. The dyke volcaniclastic deposits contain juvenile magmatic fragments (pyroclasts) suggesting a primary volcanic origin. Their petrographic characteristics are coincident with the Neostromboli products. The architecture of the infilling deposits comprises symmetrically-nested volcaniclastic units, separated by sub-vertical boundaries, which are parallel to the dyke margins. The volcanic units are composed of distinctive lithofacies. The more external facies is composed of fine and coarse ash showing sub-vertical laminations, parallel to the contact wall. The central facies comprises stratified, lithic-rich breccia and lapilli-tuff, whose stratification is sub-horizontal and convolute, discordant to the dyke margins. Only at Le Croci dyke, the final unit shows a massive tuff-breccia facies. The volcaniclastic dykes experienced a polyphasic geological evolution comprising three stages. The first phase consisted in fracturing, explosive intrusion related to magma rising and upward injection of magmatic fluids and pyroclasts. The second phase recorded the dilation of fractures and their role as pyroclastic conduits in an explosive eruption possibly coeval with the lateral collapse of the Neostromboli lava cone. Finally, in the third phase, the immediately post-eruption mass-flow remobilization of pyroclastic deposits took place on the volcano slopes.

  8. A Geochemical Investigation of the Early Cretaceous Ultrapotassic Dykes in the Raniganj Coalfields in Damodar Valley, India

    NASA Astrophysics Data System (ADS)

    Jude, T. A.

    2015-12-01

    The early Cretaceous ultrapotassic dyke rocks intruding the Permocarboniferous coal bearing Gondwana sediments of the Eastern Damodar Valley, Singhbum craton, are known for their petrographic and geochemical diversity. They remain a 'Pandora's box of petrological confusion' with a variety of exotic, and potentially diamondiferous, rocks such as lamprophyre, lamproite, orangeite and kimberlite being continuously reported from them for over one century or more. Intra-plate volcanism of this type discloses hidden information about the interior of the Earth. Samples from two dykes intruding Raniganj coalfield is studied here. The samples from Dyke1 are characterized by fine grained texture and phlogopite+apatite+K-feldspar+rutile+ankerite+dolomite+ chromite+chlorite+quartz assemblage while the samples from Dyke2 are characterized by coarse grained texture and phlogopite+ pseudomorphosed-olivine+apatite+ clinopyroxene +dolomite+ankerite+calcite+norsethite+talc+rutile+quartz+Ca-Mg-Fe-Zr silicate+K-feldspar+monazite+ perovskite assemblage. Based on the TiO2-Al2O3-FeO trends observed in phlogopites, the dykes seem to be a lamproite-orangeite transitional variety. The phlogopites observed in Dyke2 show two stages of crystallization defined by Ti-poor overgrowths on Ti-rich cores indicating that Dyke2 consolidated from a melt that fractionated from a magma which was initially emplaced at a different depth while the Dyke 1 phlogopites do not show any such sudden drop in Ti concentration in their rims indicating single stage crystallization. Ti-in-Quartz Thermometry yields temperatures between 769°C to 1115°C for Dyke1 and 779°C to 1019°C for Dyke2 which must corresponds to the emplacement and crystallization of these dykes. Trace element and isotopic ratios can be used to constrain particular mantle source characteristics of the dykes. Rb-Sr method can be used to determine the emplacement ages of these dykes.

  9. Mangrove forest against dyke-break-induced tsunami on rapidly subsiding coasts

    NASA Astrophysics Data System (ADS)

    Takagi, Hiroshi; Mikami, Takahito; Fujii, Daisuke; Esteban, Miguel; Kurobe, Shota

    2016-07-01

    Thin coastal dykes typically found in developing countries may suddenly collapse due to rapid land subsidence, material ageing, sea-level rise, high wave attack, earthquakes, landslides, or a collision with vessels. Such a failure could trigger dam-break tsunami-type flooding, or "dyke-break-induced tsunami", a possibility which has so far been overlooked in the field of coastal disaster science and management. To analyse the potential consequences of one such flooding event caused by a dyke failure, a hydrodynamic model was constructed based on the authors' field surveys of a vulnerable coastal location in Jakarta, Indonesia. In a 2 m land subsidence scenario - which is expected to take place in the study area after only about 10-20 years - the model results show that the floodwaters rapidly rise to a height of nearly 3 m, resembling the flooding pattern of earthquake-induced tsunamis. The depth-velocity product criterion suggests that many of the narrow pedestrian paths behind the dyke could experience strong flows, which are far greater than the safe limits that would allow pedestrian evacuation. A couple of alternative scenarios were also considered to investigate how such flood impacts could be mitigated by creating a mangrove belt in front of the dyke as an additional safety measure. The dyke-break-induced tsunamis, which in many areas are far more likely than regular earthquake tsunamis, cannot be overlooked and thus should be considered in disaster management and urban planning along the coasts of many developing countries.

  10. Triggered earthquakes suppressed by an evolving stress shadow from a propagating dyke

    NASA Astrophysics Data System (ADS)

    Green, Robert G.; Greenfield, Tim; White, Robert S.

    2015-08-01

    Large earthquakes can generate small changes in static stress: increases that trigger aftershock swarms, or reductions that create a region of reduced seismicity--a stress shadow. However, seismic waves from large earthquakes also cause transient dynamic stresses that may trigger seismicity. This makes it difficult to separate the relative influence of static and dynamic stress changes on aftershocks. Dyke intrusions do not generate dynamic stresses, so provide an unambiguous test of the stress shadow hypothesis. Here we use GPS and seismic data to reconstruct the intrusion of an igneous dyke that is 46 km long and 5 m wide beneath Bárðarbunga Volcano, central Iceland, in August 2014. We find that during dyke emplacement, bursts of seismicity at a distance of 5 to 15 km were first triggered and then abruptly switched off as the dyke tip propagated away from the volcano. We calculate the evolving static stress changes during dyke propagation and show that the stressing rate controls both the triggering and then suppression of earthquake rates in three separate areas adjacent to the dyke. Our results imply that static stress changes help control earthquake clustering. Similar small static stress changes may be important for triggering seismicity near geothermal areas, regions being hydrofractured and deflating oil and gas fields.

  11. Magnetic and plagioclase fabrics in Early Cretaceous mafic dykes from Namibia

    NASA Astrophysics Data System (ADS)

    Wiegand, M.; Greiling, R. O.; Kontny, A. M.; Trumbull, R. B.

    2011-12-01

    Mafic dyke swarms are major components of the South Atlantic Large Igneous Province, which originated during the Cretaceous break up of Africa and South America. We present data from the major Henties Bay-Outjo dyke swarm (HOD) in coastal and inland NW Namibia where dykes have been emplaced into the Neoproterozoic Damara mobile belt. Most of the dykes strike at a high angle to the coast (NE-SW), but minor proportions are coast-parallel (NNW-SSE), N-S or NNE-SSW. Depending on dyke thickness (ca. 0.1 m to >100 m), the rocks are variably fine- to medium grained with chilled margins. With few exceptions the dyke compositions are tholeiitic basalt to basaltic andesite. Main minerals are plagioclase, clinopyroxene, olivine, Fe-Ti oxides, and accessory apatite and sulphides. For the magnetic study, we investigated 1140 standard cylinders from 41 dykes. The samples were studied microscopically and the following magnetic properties were determined: bulk susceptibility, anisotropy of magnetic susceptibility (P'), field dependence, hysteresis, Natural Remanent Magnetization (NRM) and Anisotropy of Anhysteretic Remanent Magnetization (AARM). Magnetic susceptibilities vary between 0.16 and 151*10-3 SI units. Microscopic studies and measurements of the temperature-dependent susceptibility identify magnetite and titanomagnetite as the dominant magnetic minerals. Hysteresis loops show that the magnetic domain states of titanomagnetite are pseudo-single or a mixture of single and multi-domain. Anisotropy is mostly low, with P' values between 1.01 and 1.15. Rare values of up to 1.33 reflect a strong magmatic flow fabric. The shapes of the AMS ellipsoids range from prolate to neutral and oblate. Two main fabric types (normal and inverse) can be recognized. We used the normal fabric type samples to interpret magmatic flow fabrics and attribute steep magnetic lineations of normal fabrics to vertical magma flow and shallow magnetic lineations to horizontal flow along the dyke planes. In

  12. Experimental and numerical investigation of the effect of basaltic dykes on transient saltwater intrusion

    NASA Astrophysics Data System (ADS)

    Abdoulhalik, Antoifi; Ahmed, Ashraf; Hamill, Gerrard

    2015-04-01

    Heterogeneity in porous media is one of the major factors that control mixing zone and saltwater wedge dynamics. Basaltic dykes are natural geological structures that can significantly affect groundwater flow and solute transport in coastal aquifers. Few recent studies have investigated the effects of heterogeneity on the freshwater-saltwater mixing zone. However, most of these studies have focused on steady-state conditions. Furthermore, as per our knowledge no one has so far completed experiments to study the impact of basaltic dykes on transient saltwater intrusion. In this study, we have performed experiments in a laboratory-scale aquifer model to study saltwater intrusion process under different heterogeneous settings; a dyke was set at different locations and several values of thickness and permeability were tested. Using a variable-head groundwater system, a head difference was imposed across the porous media and images of the transient saltwater-wedge were recorded at thirty second intervals. The experimental data sets were simulated using the MODFLOW-family variable density flow code SEAWAT. The results show that under intruding-wedge conditions, the width of the mixing zone is almost two orders of magnitude larger in the presence of the dyke than it is in the homogeneous case, while it is more than ten times larger under receding-wedge conditions. A slight increase of the toe length was observed (around nine percent) in the presence of the dyke under intruding-wedge and receding-wedge conditions. When the permeability of the dyke is further reduced, it acts as an impervious barrier that almost prevents the progression of the saltwater wedge. Thus, saltwater is accumulated along the side boundary, and then forced to drain along the bottom boundary. The results highlight the significant effects of macroscopic variations in aquifer properties (such as volcanic dykes) in the temporal evolution of mixing zone dynamics (widening and narrowing) and the

  13. Detection of Magnetically Susceptible Dyke Swarms in a Fresh Coastal Aquifer

    NASA Astrophysics Data System (ADS)

    Khalil, Mohamed H.

    2014-08-01

    Groundwater constitutes the main source of freshwater in Shalatein, on the western coast of the Red Sea, in Egypt. The fresh aquifer of Shalatein is intensively dissected by shallow and deep faults associated with the occurrence of dykes and/or dyke swarms. In this context, synthesis of electrical resistivity, ground magnetics, and borehole data was implemented to investigate the freshwater aquifer condition, locate the intrusive dykes and/or dyke swarms, and demarcate the potential freshwater zones. Nine Schlumberger VES's with maximum current electrode half-spacing (AB/2) of 682 m were conducted. The subsurface was successfully delineated by general four layers. The fresh aquifer of the Quaternary and Pre-Quaternary alluvium sediments was effectively demarcated with true resistivities ranged from 30 to 105 Ωm and thickness ranged between 20 and 60 m. A ground magnetic survey comprised 35 magnetic profiles, each 7 km in length. Magnetic data interpretation of the vertical derivatives (first and second order), downward continuation (100 m), apparent susceptibility (depth of 100 m), and wavelength filters (Butterworth high-pass of wavelengths <100 m and Band-Pass of wavelengths 30-100 m) successfully distinguished the near surface structure with five major clusters of dyke swarms, whereas filters of the upward continuation (300 m) and Butterworth low-pass (wavelengths >300 m) clearly reflected the deep-seated structure. The computed depth by the 3D Euler deconvolution for geological contacts and faults (SI = 0) ranged from 14 to 545 m, whereas for dyke and sill (SI = 1), it ranged from 10 to 1,095 m. The western part of the study area is recommended as a potential freshwater zone as it is characterized by depths >100 m to the top of the dykes, higher thickness of the fresh aquifer (45-60 m), depths to the top of the fresh aquifer ranging from 25 to 40 m, and higher resistivities reflecting better freshwater quality (70-105 Ωm).

  14. Modulation of the Hormone Setting by Rhodococcus fascians Results in Ectopic KNOX Activation in Arabidopsis1[W][OA

    PubMed Central

    Depuydt, Stephen; Doležal, Karel; Van Lijsebettens, Mieke; Moritz, Thomas; Holsters, Marcelle; Vereecke, Danny

    2008-01-01

    The biotrophic actinomycete Rhodococcus fascians has a profound impact on plant development and a common aspect of the symptomatology is the deformation of infected leaves. In Arabidopsis (Arabidopsis thaliana), the serrated leaf margins formed upon infection resemble the leaf phenotype of transgenic plants with ectopic expression of KNOTTED-like homeobox (KNOX) genes. Through transcript profiling, we demonstrate that class-I KNOX genes are transcribed in symptomatic leaves. Functional analysis revealed that BREVIPEDICELLUS/KNOTTED-LIKE1 and mainly SHOOT MERISTEMLESS were essential for the observed leaf dissection. However, these results also positioned the KNOX genes downstream in the signaling cascade triggered by R. fascians infection. The much faster activation of ARABIDOPSIS RESPONSE REGULATOR5 and the establishment of homeostatic and feedback mechanisms to control cytokinin (CK) levels support the overrepresentation of this hormone in infected plants due to the secretion by the pathogen, thereby placing the CK response high up in the cascade. Hormone measurements show a net decrease of tested CKs, indicating either that secretion by the bacterium and degradation by the plant are in balance, or, as suggested by the strong reaction of 35S:CKX plants, that other CKs are at play. At early time points of the interaction, activation of gibberellin 2-oxidase presumably installs a local hormonal setting favorable for meristematic activity that provokes leaf serrations. The results are discussed in the context of symptom development, evasion of plant defense, and the establishment of a specific niche by R. fascians. PMID:18184732

  15. Regulation of the KNOX-GA Gene Module Induces Heterophyllic Alteration in North American Lake Cress[W

    PubMed Central

    Nakayama, Naomi; Seiki, Sumer; Kojima, Mikiko; Sakakibara, Hitoshi

    2014-01-01

    Plants show leaf form alteration in response to changes in the surrounding environment, and this phenomenon is called heterophylly. Although heterophylly is seen across plant species, the regulatory mechanisms involved are largely unknown. Here, we investigated the mechanism underlying heterophylly in Rorippa aquatica (Brassicaceae), also known as North American lake cress. R. aquatica develops pinnately dissected leaves in submerged conditions, whereas it forms simple leaves with serrated margins in terrestrial conditions. We found that the expression levels of KNOTTED1-LIKE HOMEOBOX (KNOX1) orthologs changed in response to changes in the surrounding environment (e.g., change of ambient temperature; below or above water) and that the accumulation of gibberellin (GA), which is thought to be regulated by KNOX1 genes, also changed in the leaf primordia. We further demonstrated that exogenous GA affects the complexity of leaf form in this species. Moreover, RNA-seq revealed a relationship between light intensity and leaf form. These results suggest that regulation of GA level via KNOX1 genes is involved in regulating heterophylly in R. aquatica. The mechanism responsible for morphological diversification of leaf form among species may also govern the variation of leaf form within a species in response to environmental changes. PMID:25516600

  16. Risk Evaluation for CO2 Geosequestration in the Knox Supergroup, Illinois Basin Final Report

    SciTech Connect

    Hnottavange-Telleen, Ken; Leetaru, Hannes

    2014-09-30

    This report describes a process and provides seed information for identifying and evaluating risks pertinent to a hypothetical carbon dioxide (CO2) capture and sequestration (CCS) project. In the envisioned project, the target sequestration reservoir rock is the Potosi Formation of the Knox Supergroup. The Potosi is identified as a potential target formation because (1) at least locally, it contains vuggy to cavernous layers that have very high porosity, and (2) it is present in areas where the deeper Mt. Simon Sandstone (a known potential reservoir unit) is absent or nonporous. The key report content is discussed in Section 3.3, which describes two lists of Features, Events, and Processes (FEPs) that should be considered during the design stage of such a project. These lists primarily highlight risk elements particular to the establishment of the Potosi as the target formation in general. The lists are consciously incomplete with respect to risk elements that would be relevant for essentially all CCS projects regardless of location or geology. In addition, other risk elements specific to a particular future project site would have to be identified. Sources for the FEPs and scenarios listed here include the iconic Quintessa FEPs list developed for the International Energy Agency Greenhouse Gas (IEAGHG) Programme; previous risk evaluation projects executed by Schlumberger Carbon Services; and new input solicited from experts currently working on aspects of CCS in the Knox geology. The projects used as sources of risk information are primarily those that have targeted carbonate reservoir rocks similar in age, stratigraphy, and mineralogy to the Knox-Potosi. Risks of using the Potosi Formation as the target sequestration reservoir for a CCS project include uncertainties about the levels of porosity and permeability of that rock unit; the lateral consistency and continuity of those properties; and the ability of the project team to identify suitable (i.e., persistently

  17. Risk Evaluation for CO{sub 2} Geosequestration in the Knox Supergroup

    SciTech Connect

    Leetaru, Hannes

    2014-01-31

    This report describes a process and provides seed information for identifying and evaluating risks pertinent to a hypothetical carbon dioxide (CO{sub 2}) capture and sequestration (CCS) project. In the envisioned project, the target sequestration reservoir rock is the Potosi Formation of the Knox Supergroup. The Potosi is identified as a potential target formation because (1) at least locally, it contains vuggy to cavernous layers that have very high porosity, and (2) it is present in areas where the deeper Mt. Simon Sandstone (a known potential reservoir unit) is absent or nonporous. The key report content is discussed in Section 3.3, which describes two lists of Features, Events, and Processes (FEPs) that should be considered during the design stage of such a project. These lists primarily highlight risk elements particular to the establishment of the Potosi as the target formation in general. The lists are consciously incomplete with respect to risk elements that would be relevant for essentially all CCS projects regardless of location or geology. In addition, other risk elements specific to a particular future project site would have to be identified. Sources for the FEPs and scenarios listed here include the iconic Quintessa FEPs list developed for the International Energy Agency Greenhouse Gas (IEAGHG) Programme; previous risk evaluation projects executed by Schlumberger Carbon Services; and new input solicited from experts currently working on aspects of CCS in the Knox geology. The projects used as sources of risk information are primarily those that have targeted carbonate reservoir rocks similar in age, stratigraphy, and mineralogy to the Knox-Potosi. Risks of using the Potosi Formation as the target sequestration reservoir for a CCS project include uncertainties about the levels of porosity and permeability of that rock unit; the lateral consistency and continuity of those properties; and the ability of the project team to identify suitable (i

  18. Thermal models of dyke intrusion during development of continent-ocean transition

    NASA Astrophysics Data System (ADS)

    Daniels, K. A.; Bastow, I. D.; Keir, D.; Sparks, R. S. J.; Menand, T.

    2014-01-01

    A consensus has emerged in recent years from a variety of geoscientific disciplines that extension during continental rifting is achieved only partly by plate stretching: dyke intrusion also plays an important role. Magma intrusion can accommodate extension at lower yield stresses than are required to extend thick, strong, unmodified continental lithosphere mechanically, thereby aiding the breakup process. Dyke intrusion is also expected to heat and thereby weaken the plate, but the spatial extent of heating and the effect of different rates of magmatic extension on the timescales over which heating occurs are poorly understood. To address this issue, a numerical solution to the heat-flow equation is developed here to quantify the thermal effects of dyke intrusion on the continental crust during rifting. The thermal models are benchmarked against a priori constraints on crustal structure and dyke intrusion episodes in Ethiopia. Finite difference models demonstrate that magmatic extension rate exerts a first-order control on the crustal thermal structure. Once dyke intrusion supersedes faulting and stretching as the principal extensional mechanism the crust will heat and weaken rapidly (less than 1 Ma). In the Main Ethiopian Rift (MER), the majority of present-day extension is focused on ∼20 km-wide Quaternary-Recent axial magmatic segments that are mostly seismogenic to mid-crustal depths and show P-wave seismic velocities characteristic of heavily intruded continental crust. When reviewed in light of our models, these observations require that no more than half of the MER's extension since ∼2 Ma has been achieved by dyke intrusion. Magmatic heating and weakening of the crust would have rendered it aseismic if dyke intrusion accounted for the entire 6 mm/yr extension rate. In the older, faster extending (16 mm/yr) Red Sea rift (RSR) in Afar, dyke intrusion is expected to have had a more dramatic impact on crustal rheology. Accordingly, effective elastic plate

  19. Videographic GIS database documentation project for Ft. Knox, Kentucky: Planning and process

    SciTech Connect

    Sullivan, R.G.; Vogt, M.C.

    1992-06-01

    The Geographic Resource Analysis Support System (GRASS), a geographic information system (GIS), has been fielded at approximately 50 US Army training installations as a land-management decision-making tool. Use of the GRASS GIS requires the compilation of numerous digital maps of environmental parameters, including elevation, soils, and hydrography. One of the uses of the GRASS GIS is to create digital graphic images that portray geographic data. A recently emerging technology called computer videographics can be used to graphically enhance GRASS-generated images, thereby creating new ways to visualize GRASS analysis results. Furthermore, videographic tools can be used to convert GRASS images into standard graphic file formats that can be displayed on low-cost personal computers, using inexpensive application software to view the images. The pilot project described in this report demonstrated the capability of videographic tools to enhance GRASS imagery through improved graphic visualization (including three-dimensional visualization) and enhanced labeling. The project also developed self-running demonstrations of GRASS imagery from Ft. Knox, Kentucky, on DOS- and Macintosh-compatible diskettes, using low-cost slide-show software to display the images.

  20. Preliminary reliability and repeatability of the Brazilian version of the Revised Knox Preschool Play Scale.

    PubMed

    Pacciulio, Amanda M; Pfeifer, Luzia I; Santos, Jair L F

    2010-06-01

    The aim of this study was to create an adaptation of the Revised Knox Preschool Play Scale (RKPPS) for the Brazilian population, as well as to apply the instrument with statistical analysis to verify the preliminary intra-rater and inter-rater reliability and repeatability of the instrument. The instructions presented by Beaton et al. regarding adaptation of instruments were followed to perform a cross-cultural adaptation of the RKPPS. A preliminary test of the Portuguese version was performed on 18 children with no motor, cognitive or sensory impairment. The video recordings of this administration were analysed on two separate occasions by two examiners within a 5-month interval, using the scores suggested by Pfeifer. The Spearman's test was used in the statistical analysis of the obtained data. The author of the RKPPS agreed with the small necessary cultural adaptations. The Spearman test revealed a high correlation coefficient and good significance levels for both intra- and inter-raters values. This study demonstrated the reliability and repeatability of the Brazilian version of the RKPPS. This is a preliminary study and further studies are needed in order to validate the scale to be administered in the Brazilian population. PMID:20099245

  1. Early sexual origins of homeoprotein heterodimerization and evolution of the plant KNOX/BELL family.

    PubMed

    Lee, Jae-Hyeok; Lin, Huawen; Joo, Sunjoo; Goodenough, Ursula

    2008-05-30

    Developmental mechanisms that yield multicellular diversity are proving to be well conserved within lineages, generating interest in their origins in unicellular ancestors. We report that molecular regulation of the haploid-diploid transition in Chlamydomonas, a unicellular green soil alga, shares common ancestry with differentiation pathways in land plants. Two homeoproteins, Gsp1 and Gsm1, contributed by gametes of plus and minus mating types respectively, physically interact and translocate from the cytosol to the nucleus upon gametic fusion, initiating zygote development. Their ectopic expression activates zygote development in vegetative cells and, in a diploid background, the resulting zygotes undergo a normal meiosis. Gsm1/Gsp1 dyads share sequence homology with and are functionally related to KNOX/BELL dyads regulating stem-cell (meristem) specification in land plants. We propose that combinatorial homeoprotein-based transcriptional control, a core feature of the fungal/animal radiation, may have originated in a sexual context and enabled the evolution of land-plant body plans. PMID:18510927

  2. Dykes, cups, saucers and sills: Analogue experiments on magma intrusion into brittle rocks

    NASA Astrophysics Data System (ADS)

    Mathieu, L.; van Wyk de Vries, B.; Holohan, Eoghan P.; Troll, Valentin R.

    2008-07-01

    Magma is transported in the crust by blade-like intrusions such as dykes, sills, saucers, and also collects in thicker laccoliths, lopoliths and plutons. Recently, the importance and great number of shallow (< 5 km) saucer-shaped intrusions has been recognized. Lopoliths and cup-shaped intrusions have also been reported in many geological contexts. Our field observations indicate that many intrusions, especially those emplaced into breccias or fractured rocks, have bulging, lobate margins and have shear faults at their bulbous terminations. Such features suggest that magma can propagate along a self-induced shear fault rather than a hydraulic tension-fracture. To investigate this we use analogue models to explore intrusion propagation in a brittle country rock. The models consist of the injection of analogue magma (honey or Golden syrup) in a granular material (sand or sieved ignimbrite) that is a good analogue for brittle or brecciated rocks. These models have the advantage (over other models that use gelatin) to well represent the properties of brittle materials by allowing both shear-faults and tension fractures to be produced at suitable stresses. In our experiments we mainly obtain vertical dykes and inverted-cone like structures that we call cup-shaped intrusions. Dykes bifurcate into cup-shaped intrusions at depths depending on their viscosity. All cup-shaped intrusions uplift a central block. By injecting against a vertical glass plate we obtain detailed observations of the intrusion propagation style. We observe that dykes commonly split and produce cup-shaped intrusions near the surface and that shear zone-related intrusions develop at the dyke tip. We conclude that many dykes propagate as a viscous indenter resulting from shear failure of host rock rather than tensional hydraulic fracturing of host rocks. The shear propagation model provides an explanation for the shape and formation of cup-shaped intrusions, saucer-sills and lopoliths.

  3. The dykes and structural setting of the volcanic front in the Lesser Antilles island arc

    NASA Astrophysics Data System (ADS)

    Wadge, G.

    1986-12-01

    The orientations of dykes from many of the islands of the Lesser Antilles island arc have been mapped. Most of these dykes can be interpreted in terms of local or regional swarms derived from specific volcanoes of known age, with distinct preferred orientations. Dykes are known from all Cenozoic epochs except the Palaeocene, but are most common in Pliocene, Miocene and Oligocene rocks. A majority of the sampled dykes are basaltic, intrude volcaniclastic host rocks and show a preference for widths of 1 1.25 m. Locally, dyke swarms dilate their hosts by up to 9% over hundreds of metres and up to 2% over distances of kilometres. The azimuths of dykes of all ages show a general NE-SW preferred orientation with a second NW-SE mode particularly in the Miocene rocks of Martinique. The regional setting for these minor intrusions is a volcanic front above a subduction zone composed of three segments: Saba-Montserrat, Guadeloupe-Martinique, St. Lucia-Grenada. The spacing of volcanic centres along this front is interpreted in terms of rising plumes of basaltic magma spaced about 30 km apart. This magma is normally intercepted at crustal depths by dioritic plutons and andesitic/dacitic magma generated there. Plumes which intersect transverse fracture systems or which migrate along the front can avoid these crustal traps. Throughout its history the volcanic front as a whole has migrated, episodically, towards the backarc at an average velocity of about 1 km/Ma. The local direction of plate convergence is negatively correlated with the local preferred orientation of dykes. The dominant NE-SW azimuth mode corresponds closely to the direction of faulting in the sedimentary cover of the backarc and the inferred tectonic fabric of the oceanic crust on which the arc is founded. A generalised model of the regional stress field that controls dyke intrusion outside of the immediate vicinity of central volcanic vents is proposed, in which the maximum horizontal stress parallels the

  4. Late Cretaceous -Early Tertiary dyke swarm of North Greenland it's age, origins and tectonic significance

    NASA Astrophysics Data System (ADS)

    Manby, Geoffrey

    2014-05-01

    North Greenland is characterized by N-S, NW-SE and E-W trending swarms of mafic dykes which pre- and post date Kap Washington suite of bimodal lavas, ash flows and tuffs. Both rock groups are over-thrust by north vergent thrust sheets of Early Palaeozoic age rocks which record low grade Ellesmerian (Carboniferous) metamorphism and deformation. Laser ablation Ar/Ar ages of 58Ma and 62Ma obtained from thrust fault generated mylonites suggest that magmatism must have effectively ceased by then as no undeformed dykes have been found to cross the thrust planes. High resolution PMAP aeromagnetic surveys for 1989 and 1997-98 show that linear magnetic anomalies parallel to the dense N-S trending dyke swarm of Nansen Land can be traced out onto the Lincoln Sea platform suggesting the dykes are part of the predominantly offshore failed rift magmatic domain which lies central to the southern ends of Alpha ridge, the Lomonosov Ridge, the Markarov Basin, the Amundsen Basin and the Morris-Jessup Plateau. In addition the dykes to the SW of the Mascart Inlet appear to extend undisturbed by faulting 150km onto the Lincoln Sea platform north of Ellesmere Island. The curved ca EW deep negative anomaly which truncates the dyke swarm offshore to the north of the Kap Canon Fault zone together with a similar anomaly along the Harder fjord Fault Zone and its western continuation to the Kap Ramsey Fault appear to constitute the limits of Eurekan thrust belt of North Greenland. Stress tensor analyses of all Eurekan fault plane populations show a consistent N-S to NNW-SSE pure compression pattern orthogonal to the main thrust faults and near parallel to the main dyke trend. Rb/Sr, and Ar/Ar ages obtained from biotite separates, with U/Th ages from apatite-feldspar pairs suggest the dykes range in age from ca 103Ma to 69Ma. The peralkaline affinity of the dyke swarm is similar to that of many other rift generated basalts. Nd, Sr and a small number of Pb isotope ratios have been determined for

  5. Dyke-path formation in relation to the eruptions of Eyjafjallajökull 2010 and Bardarbunga-Holuhraun 2014

    NASA Astrophysics Data System (ADS)

    Gudmundsson, Agust

    2015-04-01

    Dykes are extension fractures and form when the magmatic overpressure is high enough to rupture (break) the host rock. Their formation is entirely analogous to that of many joints and human-made hydraulic fractures, such as are used to increase permeability in reservoirs. When generating their paths, dykes use existing weaknesses (e.g., cooling joints) in the host rock. The maximum depth of large tension fractures below the surface of a rift zone, however, is mostly less than a few hundred metres. If the fractures extend to greater depths, they must change into closed normal faults which are generally not used as magma paths. There are thus no large tension fractures or wide-open faults at great depths ready to be filled with magma to form a dyke. While magma flow in dykes, as in other fluid-driven fractures, is at any point in various directions dyke segmentation may indicate the overall large-scale flow direction. Thus, dykes composed of large-spaced disconnected segments in lateral sections are primarily formed in vertical magma flow at segmentation depth whereas those composed of large-spaced disconnected segments in vertical sections are primarily formed in lateral magma flow. The far-field displacement and stress fields of segmented dykes are similar to those generated by single, continuous dykes of similar dimensions, particularly when the distances between the nearby tips of the segments become small in comparison with segment lengths. Most dykes become arrested and never supply magma to eruptions. Feeder-dykes normally reach the surface only along parts of their lengths (strike-dimensions). The volumetric flow or effusion rate of magma through a feeder-dyke or volcanic fissure depends on the aperture (opening) of the dyke or fissure in the 3rd power. All these theoretical and observational results are here applied to the dyke emplacements associated with the eruptions of Eyjafjallajökull 2010 and Bardarbunga-Holuhraun 2014. The results make it possible to

  6. Formation conditions of leucogranite dykes and aplite-pegmatite dykes in the eastern Mt. Capanne plutonic complex (Elba, Italy): fluid inclusion studies in quartz, tourmaline, andalusite and plagioclase

    NASA Astrophysics Data System (ADS)

    Bakker, Ronald J.; Schilli, Sebastian E.

    2016-02-01

    Leucogranite and aplite-pegmatite dykes are associated with the Mt. Capanne pluton (Elba) and partly occur in the thermally metamorphosed host rock (serpentinites). Crystallization conditions of these dykes in the late magmatic-hydrothermal stage are estimated from fluid inclusion studies and mineralogical characterisation, obtained from detailed microthermometry, Raman spectroscopy, and electron microprobe analyses. Fluid inclusion assemblages are analysed in andalusite, quartz, and plagioclase from the leucogranite dykes, and in tourmaline and quartz from the aplite-pegmatite dykes. The fluid inclusion assemblages record multiple pulses of low salinity H2O-rich magmatic and reduced metamorphic fluid stages. Magmatic fluids are characterized by the presence of minor amounts of CO2 and H3BO3, whereas the metamorphic fluids contain CH4 and H2. The highly reduced conditions are also inferred from the presence of native arsenic in some fluid inclusions. Several fluid inclusion assemblages reveal fluid compositions that must have resulted from mixing of both fluid sources. In leucogranite dykes, magmatic andalusite contains a low-density magmatic CO2-rich gas mixture with minor amounts of CH4 and H2. Accidentally trapped crystals (mica) and step-daughters (quartz and diaspore) are detected in some inclusions in andalusite. The first generation of inclusions in quartz that crystallized after andalusite contains a highly reduced H2O-H2 mixture and micas. The second type of inclusions in quartz from the leucogranite is similar to the primary inclusion assemblage in tourmaline from the aplite-pegmatite, and contains up to 4.2 mass% H3BO3, present as a sassolite daughter crystal or dissolved ions, in addition to a CO2-CH4 gas mixture, with traces of H2, N2, H2S, and C2H6. H2O is the main component of all these fluids ( x = 0.91 to 0.96) with maximally 7 mass% NaCl. Some accidentally trapped arsenolite and native arsenic are also detected. These fluids were trapped in the

  7. Dyke-Davidoff-Masson syndrome: imaging features with illustration of two cases

    PubMed Central

    Rani, Jyotsna Y.

    2015-01-01

    Dyke-Davidoff-Masson syndrome is a rare entity characterized by hemi cerebral atrophy/hypoplasia secondary to brain insult in fetal or early childhood period along with ipsilateral compensatory osseous hypertrophy and contralateral hemiparesis. We present two cases of this uncommon condition and discuss its imaging features, differential diagnosis, treatment options and prognosis. PMID:26029650

  8. Geochemistry and petrogenesis of proterozoic mafic dykes in north Kerala, southwestern Indian Shield - Preliminary results

    NASA Technical Reports Server (NTRS)

    Radhakrishna, T.; Gopakumar, K.; Murali, A. V.; Mitchell, J. G.

    1991-01-01

    Mafic dyke intrusions occur in three distinct orientations ( NNW-SSE and NW-SE and NE-SW) in north Kerala regions, the southwestern part of the Indian Shield. Dating of two NNW-SSE trending dykes by K-Ar method has yielded Middle Proterozoic ages (ca. 1660 Ma and ca. 1420 Ma respectively). Our initial geochemical results on these dyke rocks (0.65-0.15 wt pct K2O, 0.37-0.38 wt pct P2O5, 3.30-1.00 wt pct TiO2, 11-1 p.p.m. Rb, 250-90 p.p.m. Sr, 230-40 p.p.m. Ba, 160-40 p.p.m. Zr, and 30-10 x chondrite rare earth elemental abundances) indicate a transitional character between abyssal and plateau tholeiites. Petrogenetic modelling suggests that the dyke compositions have been derived by different degrees of partial melting of a heterogenous source mantle. The mantle sources with accessory amphibole and/or garnet, variably enriched in LREE and LIL elements, are compatible with the observed geochemical data.

  9. The 2004 dyke-fault interaction at Dallol, northern Afar (Ethiopia)

    NASA Astrophysics Data System (ADS)

    Nobile, A.; Pagli, C.; Keir, D.; Wright, T.; Ruch, J.; Acocella, V.

    2012-04-01

    The 2005 Dabbahu intrusive event in Afar highlighted the importance of magma in controlling rifting along divergent plate boundaries. Here we show that a further intrusive event occurred in late 2004 at Dallol, along the axis of the Red Sea Rift in northern Afar. Dallol consists of an hydrothermal area lacking significant volcanic activity at the northern end of the Erta Ale volcanic segment. We use InSAR and seismicity data to constrain the geometric and kinematic features of the intrusion, as well as its possible effects. The dyke intruded a 6 km portion of the rift, from Dallol volcano, which subsided, to the south. The intrusion was accompanied by a seismic sequence, including a Mw 5.5 earthquake on 22 October. The larger events were registered by several seismic stations worldwide and located by the International Seismological Center (ISC). InSAR data from Envisat allow us to measure the surface deformation associated with these events. An inversion for a simple elastic model suggests that a ~3m wide and ~46km3 volume dyke was accompanied by fault slip. Seismicity observations suggest that the Mw 5.5 earthquake was triggered by the dyke intrusion. These results at Dallol provide the northernmost evidence of dyke-induced extension in Afar, occurring shortly before the 2005 event at Dabbahu.

  10. Regulation, overexpression, and target gene identification of Potato Homeobox 15 (POTH15) - a class-I KNOX gene in potato.

    PubMed

    Mahajan, Ameya S; Kondhare, Kirtikumar R; Rajabhoj, Mohit P; Kumar, Amit; Ghate, Tejashree; Ravindran, Nevedha; Habib, Farhat; Siddappa, Sundaresha; Banerjee, Anjan K

    2016-07-01

    Potato Homeobox 15 (POTH15) is a KNOX-I (Knotted1-like homeobox) family gene in potato that is orthologous to Shoot Meristemless (STM) in Arabidopsis. Despite numerous reports on KNOX genes from different species, studies in potato are limited. Here, we describe photoperiodic regulation of POTH15, its overexpression phenotype, and identification of its potential targets in potato (Solanum tuberosum ssp. andigena). qRT-PCR analysis showed a higher abundance of POTH15 mRNA in shoot tips and stolons under tuber-inducing short-day conditions. POTH15 promoter activity was detected in apical and axillary meristems, stolon tips, tuber eyes, and meristems of tuber sprouts, indicating its role in meristem maintenance and leaf development. POTH15 overexpression altered multiple morphological traits including leaf and stem development, leaflet number, and number of nodes and branches. In particular, the rachis of the leaf was completely reduced and leaves appeared as a bouquet of leaflets. Comparative transcriptomic analysis of 35S::GUS and two POTH15 overexpression lines identified more than 6000 differentially expressed genes, including 2014 common genes between the two overexpression lines. Functional analysis of these genes revealed their involvement in responses to hormones, biotic/abiotic stresses, transcription regulation, and signal transduction. qRT-PCR of selected candidate target genes validated their differential expression in both overexpression lines. Out of 200 randomly chosen POTH15 targets, 173 were found to have at least one tandem TGAC core motif, characteristic of KNOX interaction, within 3.0kb in the upstream sequence of the transcription start site. Overall, this study provides insights to the role of POTH15 in controlling diverse developmental processes in potato. PMID:27217546

  11. KNOX genes influence a gradient of fruit chloroplast development through regulation of GOLDEN2-LIKE expression in tomato.

    PubMed

    Nadakuduti, Satya Swathi; Holdsworth, William L; Klein, Chelsey L; Barry, Cornelius S

    2014-06-01

    The chlorophyll content of unripe fleshy fruits is positively correlated with the nutrient content and flavor of ripe fruit. In tomato (Solanum lycopersicum) fruit, the uniform ripening (u) locus, which encodes a GOLDEN 2-LIKE transcription factor (SlGLK2), influences a gradient of chloroplast development that extends from the stem end of the fruit surrounding the calyx to the base of the fruit. With the exception of the u locus, the factors that influence the formation of this developmental gradient are unknown. In this study, characterization and positional cloning of the uniform gray-green (ug) locus of tomato reveals a thus far unknown role for the Class I KNOTTED1-LIKE HOMEOBOX (KNOX) gene, TKN4, in specifying the formation of this chloroplast gradient. The involvement of KNOX in fruit chloroplast development was confirmed through characterization of the Curl (Cu) mutant, a dominant gain-of-function mutation of TKN2, which displays ectopic fruit chloroplast development that resembles SlGLK2 over-expression. TKN2 and TKN4 act upstream of SlGLK2 and the related gene ARABIDOPSIS PSEUDO RESPONSE REGULATOR 2-LIKE (SlAPRR2-LIKE) to establish their latitudinal gradient of expression across developing fruit that leads to a gradient of chloroplast development. Class I KNOX genes typically influence plant morphology through maintenance of meristem activity, but this study identifies a role for TKN2 and TKN4 in specifically influencing chloroplast development in fruit but not leaves, suggesting that this fundamental process is differentially regulated in these two organs. PMID:24689783

  12. Dyke Intrusion and Arrest in Harrat Lunayyir, western Saudi Arabia, in April-July 2009

    NASA Astrophysics Data System (ADS)

    Jónsson, Sigurjón; Pallister, John; McCausland, Wendy; El-Hadidy, Salah

    2010-05-01

    Dyke intrusion in Harrat Lunayyir (also known as Harrat Al-Shaqah), one of the volcanic provinces in Saudi Arabia, caused numerous small to moderate-sized earthquakes and extensive surface faulting in April-July 2009. The most intensive earthquake activity took place on 17-20 May when six magnitude 4.6-5.7 earthquakes occurred, resulting in some structural damage and prompting the Saudi civil protection authorities to evacuate more than 30000 people from the area. While the earthquake activity significantly decreased after 20 May, it continued throughout June and July with a few earthquakes as large as magnitude ~4, before quieting down in August. Much of what we have learned about the activity comes from interferometric satellite radar (InSAR) observations and from analysis of the seismic data collected by a broadband seismic network that was installed soon after the earthquake swarm started in April. The InSAR data show that large-scale (40 km × 40 km) east-west extension of over 1 m took place as well as broad uplift amounting to over 40 cm. The center of the uplifted area was transected by northwest-trending graben subsidence of over 50 cm, bounded by a single fault to the southwest showing up to ~1 m of faulting and by multiple smaller faults and cracks to the northeast. The observed deformation is well explained with a near-vertical dyke intrusion and graben-bounding normal faulting. The strike of the model dyke is NNW-SSE, parallel to the Red Sea rift, and its volume is about 0.13 km3. The modeling suggests that the shallowest part of the dyke reached within only 2 km of the surface, right below where the graben is the narrowest and under an area with a number of cinder cones from previous volcanic events. The main graben-bounding surface fault, to the southwest of the dyke, grew from ~3 km to ~8 km with the magnitude 5.7 earthquake on 19 May. Soon after this event the overall earthquake activity dramatically declined. The faulting appears to have

  13. Geometry and emplacement of the Late Cretaceous mafic dyke swarms on the islands in Zhejiang Province, Southeast China: Insights from high-resolution satellite images

    NASA Astrophysics Data System (ADS)

    Chen, Ning-hua; Dong, Jin-jin; Chen, Jian-yu; Dong, Chuan-wan; Shen, Zhong-yue

    2014-01-01

    The geology of Zhejiang coastal area in Southeast China is characterized by numerous Late Mesozoic intrusive rocks and widespread mafic dyke swarms, which indicate continental lithospheric extensional events during the Jurassic and Cretaceous. This work is focused on using multisource high-resolution remote sensing images (Worldview2, Geoeye1 and Quickbird2) to identify the geometry, morphology and location of previously undocumented and poorly understood dyke swarms exposed on the islands in Zhejiang Province. The geometry of each dyke is described by its strike, length and thickness. The spatial distribution of the dyke density and crustal dilation are obtained based on the statistics of 774 extracted mafic dykes. Field surveys are performed in some islands in order to analyze the detailed geometric features and assess the interpretative accuracy. The spectral measurement and analysis of mafic dykes are performed as well for remote sensing imagery processing and lithological interpretation. The results show that the frequency distributions of the length and thickness of dykes follow power law curves. The maximum and mean dyke thicknesses are 11.2 m and 1.43 m, respectively. The crustal dilation of the islands ranges from 0.09% to 7.4%. From the north to the south islands, the dilation decreases gradually. The dyke frequency and density have the same distribution as the dilation. According to 40Ar-39Ar age (Zhongshanjie archipelago) and U-Pb zircon age (Sijiao Island) of the mafic dyke, the dyke swarms on the eastern Zhejiang islands emplaced at around 87-97 Ma. The cross-cutting relationships of dykes and host rocks show that the mafic dyke swarms have close spatial correlations with granite. The dykes stretch in various directions whereas the NE-trending dykes dominate. Our research reveals four intrusive events that imply the crustal extension and intermittent variation of the regional stress field in the coastal area of southeastern China in the Late

  14. Revisiting van Hiele

    ERIC Educational Resources Information Center

    Papademetri-Kachrimani, Chrystalla

    2012-01-01

    In this paper I argue my opposition to the consensus which has dominated the literature that young children view shapes as a whole and pay no attention to shape structure and that geometrical thinking can be described through a hierarchical model formed by levels. This consensus is linked to van Hiele's weok by van Hiele-based research. In the…

  15. Triggering of microearthquakes in Iceland by volatiles released from a dyke intrusion

    NASA Astrophysics Data System (ADS)

    Martens, Hilary R.; White, Robert S.

    2013-09-01

    We suggest that carbon dioxide exsolved from a mid-crustal basaltic dyke intrusion in Iceland migrated upwards and triggered shallow seismicity by allowing failure on pre-existing fractures under the relatively low elastic stresses (100-200 kPa; 1-2 bar) generated by the dyke inflation. Intense swarms of microseismicity accompanied magmatic intrusion into a dyke at depths of 13-19 km in the crust of Iceland's Northern Volcanic Rift Zone during 2007-2008. Contemporaneously, a series of small normal earthquakes, probably triggered by elastic stresses imposed by the dyke intrusion, occurred in the uppermost 4 km of crust: fault plane solutions from these are consistent with failure along the extensional fabric and surface fissure directions mapped in the area, suggesting that the faults failed along existing rift zone fabric even though the mid-crustal dyke is highly oblique to it. Several months after the melt froze in the mid-crust and seismicity associated with the intrusion had ceased, an upsurge in shallow microseismicity began in the updip projection of the dyke near the brittle-ductile transition at 6-7 km depth below sea level. This seismicity is caused by failure on right-lateral strike-slip faults, with fault planes orientated 23 ± 3°, which are identical with the 24 ± 2° orientation in this area of surface fractures and fissures caused by plate spreading and extension of the volcanic rift zone. However, these earthquakes have T-axes approximately aligned with the opening direction of the dyke, and the right-lateral sense of failure is opposite that of regional strike-slip faults. We suggest that the fractures occurred along pre-existing weaknesses generated by the pervasive fabric of the rift zone, but that the dyke opening in the mid-crust beneath it caused right-lateral failure. The seismicity commenced after a temporal delay of several months and has persisted for over 3 yr. We propose that fluids exsolved from the magma in the dyke, primarily carbon

  16. Geophysical characteristics of Aswa shear, Nagasongola discontinuity and ring dyke complex in Uganda

    NASA Astrophysics Data System (ADS)

    Ruotoistenmäki, Tapio

    2014-05-01

    During the years 2008-2012, the geology of most of Uganda was studied within the framework of the Sustainable Management of Mineral Resources Project (SMMRP). During the project, comprehensive airborne magnetic and radiometric surveys were flown over the entire country and geological, petrophysical, geochemical sampling, geological field studies and detailed geophysical field profiles were undertaken in selected sub-areas. This report concentrates on the geophysical properties of three major geophysical structures in the area considered during the project: the Pan-African (0.6-0.7 Ga) Aswa shear zone and Nagasongola discontinuity (suture), and the 1.36 Ga Uganda-Tanzania semi-circular ‘ring dyke' complex. The geophysical profiles across the Aswa shear indicate that the fault zone dips steeply, at about 60° to NE. The structure represents a magnetic, gravimetric (density), radiometric and topographic discontinuity, all diminishing from SW to NE across the zone. The zone is also characterized by complex radiometric anomalies. A schematic reconstruction of the evolution of the Aswa shear zone on the magnetic map suggests a nearly 60 km sinistral horizontal component of displacement along the zone. The Nakasongola zone is another distinct magnetic, gravimetric and radiometric discontinuity, interpreted to represent a collision (suture) zone, where the northern, low-magnetic block has been thrust over the southern, denser and more magnetic block. Modeling of gravity and magnetic data are consistent with a geometry in which the southern, magnetic and high-density block dips gently to great depth beneath the northern block. Bedrock exposures in both the Aswa shear zone and Nagasongola zone areas indicate a very protracted and complex history of tectonic processes commencing in the Archaean-Paleoproterozoic era and culminating in Pan-African orogenies. Both, the Aswa shear zone and Nagasongola discontinuity are cut by continuous younger dykes that show no signs of

  17. Paleomagnetism of the Grenville diabase dyke swarm and implications for the mid Vendian paleolatitude of Laurentia

    NASA Astrophysics Data System (ADS)

    Buchan, K. L.; Ernst, R. E.; Kumarapeli, P. S.

    2004-05-01

    The Vendian-early Cambrian drift of Laurentia is important for theories of `Snowball Earth' and the continental breakup that formed the Iapetus Ocean. However, estimates of Laurentia's paleolatitude in this period differ widely. Some authors have proposed that Laurentia remained in low latitude throughout this period, whereas others have supported rapid drift of the continent from low to high and back to low latitude. To assist in evaluating these models, a paleomagnetic study was conducted on the mid Vendian Grenville dyke swarm of southeastern Laurentia. This 700 km long swarm was emplaced along the Ottawa graben, an aulacogen associated with rifting that preceded the opening of the Iapetus Ocean. The swarm was the subject of an early paleomagnetic study by Murthy (1971). More recently, U-Pb baddeleyite and zircon ages of ca. 590 Ma have been described for three Grenville dykes (Kamo et al. 1995). At one of these sites, on the `Mattawa' dyke, a positive paleomagnetic baked contact test was also reported (Hyodo and Dunlop 1993). In that detailed test thermoremanent overprinting in the zone of hybrid magnetization was shown to match that expected from heat conduction for a cooling dyke. Nevertheless, Hyodo and Dunlop suggested that the steep down remanence in the dyke, although primary, was likely acquired during a geomagnetic excursion because it did not appear to fit the then-available polar wander path. In our study, paleomagnetic sampling was carried out at 36 sites, including all three dated locations. A detailed analysis has been completed for the dated sites and preliminary analysis for the remaining sites. A stable steep down remanence was obtained for all samples in the Mattawa dyke, and in most samples from a second dated site. The third dated site is less stably magnetized and has not yielded a usable remanence direction. Ten additional sites yield stable steep down or occasionally steep up remanences. The presence of a steep remanence in two dated dykes

  18. 40Ar/39Ar geochronology and geochemistry of the Central Saurashtra mafic dyke swarm: insights into magmatic evolution, magma transport, and dyke-flow relationships in the northwestern Deccan Traps

    NASA Astrophysics Data System (ADS)

    Cucciniello, Ciro; Demonterova, Elena I.; Sheth, Hetu; Pande, Kanchan; Vijayan, Anjali

    2015-05-01

    The Central Saurashtra mafic dyke swarm in the northwestern Deccan Traps contains a few picrites, several subalkalic basalts and basaltic andesites, and an andesite. We have obtained precise 40Ar/39Ar ages of 65.6 ± 0.2 Ma, 66.6 ± 0.3, and 62.4 ± 0.3 Ma (2σ errors) for three of the dykes, indicating the emplacement of the swarm over several million years. Mineral chemical and whole-rock major and trace element and Sr-Nd isotopic data show that fractional crystallization and crystal accumulation were important processes. Except for two dykes (with ɛNd t values of -8.2 and -12.3), the magmas were only moderately contaminated by continental crust. The late-emplaced (62.4 Ma) basalt dyke has compositional characteristics (low La/Sm and Th/Nb, high ɛNd t of +4.3) suggesting little or no crustal contamination. Most dykes are low-Ti and a few high-Ti, and these contrasting Ti types cannot be produced by fractional crystallization processes but require distinct parental magmas. Some dykes are compositionally homogeneous over tens of kilometers, whereas others are heterogeneous, partly because they were formed by multiple magma injections. The combined field and geochemical data establish the Sardhar dyke as ≥62 km long and the longest in Saurashtra, but this and the other Central Saurasthra dykes cannot have fed any of the hitherto studied lava-flow sequences in Saurashtra, given their very distinct Sr-Nd isotopic compositions. As observed previously, high-Ti lavas and dykes only outcrop east-northeast of a line joining Rajkot and Palitana, probably because of underlying enriched mantle at ~65 Ma.

  19. Evidences for multiple remagnetization of Proterozoic dykes from Iguerda inlier (Anti-Atlas Belt, Southern Morocco)

    NASA Astrophysics Data System (ADS)

    Neres, Marta; Silva, Pedro F.; Ikene, Moha; Martins, Sofia; Hafid, Ahmid; Mata, João; Almeida, Francisco; Youbi, Nasrrddine; Boumehdi, Ahmed

    2016-04-01

    Paleomagnetic data able to constrain the paleoposition of the West African Craton (WAC) during Paleo-Mesoproterozoic are absent, mainly due to gaps on the sedimentary record and intense remagnetizations. Dykes that intrude several Proterozoic inliers of WAC in the Anti-Atlas Belt (southern Morocco) have recently been subjected to geochronological studies, which revealed ages between Paleoproterozoic and early Neoproterozoic. Therefore, these dykes represent a window of opportunity for paleomagnetic studies aiming to infer about the paleoposition of WAC during Proterozoic. On this scope we conducted a paleomagnetic study on seven Proterozoic dykes of the Iguerda inlier. We determined the paleomagnetic directions and evaluated their meaning by rock magnetic and mineral analyses, complemented by petrographic observations. Results revealed that these rocks record the presence of a complex history of remagnetization events, mostly assigned to several Phanerozoic thermal/chemical events. In particular, we found components assigned to the late stages of Pan African orogeny (s.l.), to the Late Carboniferous Variscan orogeny, and to more recent events. The recognized remagnetization processes are related to widespread metamorphic events under greenschist facies followed by low-temperature oxidation, both responsible for the formation of new magnetic phases (magnetite and hematite). The primary (magmatic) thermo-remanent magnetization of the dykes was obliterated during these events through multiple thermal and chemical remagnetizations. For only one dyke the presence of primary magnetization is possible to infer, though not to confirm, and would place WAC at an equatorial position around 1750 Ma. The authors wish to acknowledge FCT (Portugal) - CNRST (Morocco) bilateral agreement for its major contribution without which this work wouldn't be possible. Publication supported by project FCT UID/GEO/50019/2013 - Instituto Dom Luiz.

  20. Magma flow pattern in dykes of the Azores revealed by anisotropy of magnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Moreira, M. A.; Geoffroy, L.; Pozzi, J. P.

    2015-02-01

    The localization of magma melting areas at the lithosphere bottom in extensional volcanic domains is poorly understood. Large polygenetic volcanoes of long duration and their associated magma chambers suggest that melting at depth may be focused at specific points within the mantle. To validate the hypothesis that the magma feeding a mafic crust, comes from permanent localized crustal reservoirs, it is necessary to map the fossilized magma flow within the crustal planar intrusions. Using the AMS, we obtain magmatic flow vectors from 34 alkaline basaltic dykes from São Jorge, São Miguel and Santa Maria islands in the Azores Archipelago, a hot-spot related triple junction. The dykes contain titanomagnetite showing a wide spectrum of solid solution ranging from Ti-rich to Ti-poor compositions with vestiges of maghemitization. Most of the dykes exhibit a normal magnetic fabric. The orientation of the magnetic lineation k1 axis is more variable than that of the k3 axis, which is generally well grouped. The dykes of São Jorge and São Miguel show a predominance of subhorizontal magmatic flows. In Santa Maria the deduced flow pattern is less systematic changing from subhorizontal in the southern part of the island to oblique in north. These results suggest that the ascent of magma beneath the islands of Azores is predominantly over localized melting sources and then collected within shallow magma chambers. According to this concept, dykes in the upper levels of the crust propagate laterally away from these magma chambers thus feeding the lava flows observed at the surface.

  1. Structural and palaeomagnetic Analysis of the Koolau Dyke Swarm Exposed in the Kapa'a Quarry, Oahu: Implications for the Structural Evolution of Kilauea - Type Volcanic Rift Zones.

    NASA Astrophysics Data System (ADS)

    Day, S. J.; Herrero-Bervera, E.; Knight, M. D.

    2003-12-01

    The Koolau dyke swarms, exposed within the Kailua embayment on the northeastern side of Oahu, have been interpreted as feeders to rift zones in the Koolau volcano, analagous to the rift zones of Kilauea volcano (Walker, 1987), that developed prior to the giant Nuuanu lateral collapse at about 2.0 Ma. Systematic determination of cross-cutting relationships between Koolau dykes has proved difficult because of dense vegetation and rapid weathering in the humid tropical climate of windward Oahu. For this study we have concentrated on exposures of the dykes in the large (450 m wide and 200m deep) Kapa'a quarry, about 3 km NE of the near vertical Nuuanu Pali escarpment. Kapa'a quarry was chosen for this study because it has large, freshly exposed sections nearly perpendicular to the dyke swarm trend in hydrothermally altered but largely unweathered rocks. The hydrothermal alteration indicates that the dykes exposed in the quarry were emplaced well below a high water table resulting from trapping of water between dykes: this high water table may have played a part in the eventual collapse. The excellent exposure at Kapa'a allows systematic, accurate determination of structural data and cross-cutting relationships for every dyke in the measured sections. These data were collected for 171 dykes, of which 10 dykes have so far been sampled for palaeomagnetic analysis (i.e remanence and petrofabrics). Most dykes at Kapa'a dip steeply, from around 70 degrees SW (away from the unstable flank of the volcano) through vertical to 50 degrees NE (towards the unstable flank). NE dipping dykes are more abundant overall. Groups of SW - dipping dykes alternate with groups of subvertical to NE - dipping dykes, suggesting a quasi-periodic alternation of the stress regime within the Koolau volcano. Dyke dilations were typically subhorizontal. A final group of dykes, cross-cutting all the others, dip from 50 degrees NE to as little as 35 degrees NE, and dilated in a steeply SW - plunging

  2. ArcGIS studies and field relationships of Paleoproterozoic mafic dyke swarms from the south of Devarakonda area, Eastern Dharwar Craton, southern India: Implications for their relative ages

    NASA Astrophysics Data System (ADS)

    Samal, Amiya K.; Srivastava, Rajesh K.; Sinha, Lokesh K.

    2015-07-01

    Google Earth Image and cross-cutting field relationships of distinct Paleoproterozoic mafic dykes from south of Devarakonda area in the Eastern Dharwar Craton has been studied to establish relative emplacement ages. The Devarakonda, covering an area of ˜700 km2, shows spectacular cross-cutting field relationships between different generations of mafic dykes, and is therefore selected for the present study. Although some recent radiometric age data are available for distinct Paleoproterozoic mafic dykes from the Eastern Dharwar Craton, there is no analogous age data available for the study area. Therefore, relative age relationships of distinct mafic dykes have been established for the study area using cross-cutting field relationships and GIS techniques, which shows slightly different picture than other parts of the Eastern Dharwar Craton. It is suggested that NE-SW trending mafic dykes are youngest in age (probably belong to ˜1.89 Ga dyke swarm), whereas NNW-SSE trending mafic dykes have oldest emplacement age. Further, the NNW-SSE mafic dykes are older to the other two identified mafic dyke swarms, i.e., WNW-ESE (˜2.18 Ga) and N-S trending (˜2.21 Ga) mafic dyke swarms, as dykes of these two swarms cross-cut a NNW-SSE dyke. It provides an evidence for existence of a new set of mafic dykes that is older to the ˜2.21 Ga and probably younger to the ˜2.37 Ga swarm. Present study also supports existence of two mafic dyke swarms having similar trend (ENE-WSW to NE-SW) but emplaced in two different ages (one is ˜2.37 Ga and other ˜1.89 Ga).

  3. New Paleomagnetic Results from Late Cretaceous Volcanics and Dykes, SouthWest India

    NASA Astrophysics Data System (ADS)

    Perrin, M.; Joseph, M.; Monie, P.

    2015-12-01

    Late Cretaceous magmatism is widely distributed along the south west coast of India, mainly in the form of dyke intrusions. Most prominent dykes were emplaced around 65 Ma and are distributed in central Kerala, north Kerala and Goa. The strike trend of these dykes is NW-SE in central Kerala, whereas two orthogonal directions with NW-SE and NE-SW trends are found in north Kerala. In Goa region, they are mostly perpendicular to the coast. 25 sites (232 samples) have been collected in Kerala and Goa areas. A subordinate magmatism, around 90 Ma in age, is also traced in Agali area and St Mary Archipelago off the Malpe coast. Nine dykes (79 samples) with NW-SE trend were collected, and 9 flows (63 samples) from 8 different islands of the St Mary Archipelago. Finally, following some field evidences, the Ezhimala igneous complex, south of St Mary Islands, that occurs as a linear ridge with a NNW-SSE trend and consists mainly of granite, granophyre and gabbro, cut by dolerites, was also sampled (9 sites, 58 samples) despite its inferred Precambrian age (Rb-Sr determinations at 678 Ma). Finally, in order to constrain the duration of the Deccan volcanism, some of the younger and of the older flows (55 sites, 309 samples) were also collected. Most of the doleritic dykes are fine to medium grained with typical mineral assemblages of plagioclase, augite, olivine, and Fe-Ti oxides. All the mafic dykes of Kerala plot within the sub-alkalic field but three groups can be distinguished chemically. Fe-Ti oxides are found either as early inclusions within pyroxene or as interstitial and may constitute the late crystallization phases. Selected specimens from each site were subjected to low and high temperature susceptibility measurements to define the magnetic carriers and the thermal stability of the samples. They have indicated titanomagnetite as the main carrier of magnetization. Palaeomagnetic measurements were carried out by detailed step-wise alternating field and thermal

  4. Ectopic expression of class 1 KNOX genes induce and adventitious shoot regeneration and alter growth and development of tobacco (Nicotiana tabacum L) and European plum (Prunus domestica L)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Transgenic plants of tobacco (Nicotiana tabacum L) and plum (Prunus domestica L) were produced by transforming with apple class 1 KNOX genes (MdKN1 and MdKN2) or corn KN1 gene. Transgenic tobacco plants were regenerated in vitro from transformed leaf discs cultured in a tissue medium lacking cytoki...

  5. VAN method lacks validity

    NASA Astrophysics Data System (ADS)

    Jackson, David D.; Kagan, Yan Y.

    Varotsos and colleagues (the VAN group) claim to have successfully predicted many earthquakes in Greece. Several authors have refuted these claims, as reported in the May 27,1996, special issue of Geophysical Research Letters and a recent book, A Critical Review of VAN [Lighthill 1996]. Nevertheless, the myth persists. Here we summarize why the VAN group's claims lack validity.The VAN group observes electrical potential differences that they call “seismic electric signals” (SES) weeks before and hundreds of kilometers away from some earthquakes, claiming that SES are somehow premonitory. This would require that increases in stress or decreases in strength cause the electrical variations, or that some regional process first causes the electrical signals and then helps trigger the earthquakes. Here we adopt their notation SES to refer to the electrical variations, without accepting any link to the quakes.

  6. Van Gogh Sun

    NASA Video Gallery

    Nicholeen Viall, a solar scientist at NASA's Goddard Space Flight Center creates images of the sun reminiscent of Van Gogh, but it's science, not art. The color of each pixel contains a wealth of i...

  7. Radial patterns of bitumen dykes around Quaternary volcanoes, provinces of northern Neuquén and southernmost Mendoza, Argentina

    NASA Astrophysics Data System (ADS)

    Cobbold, Peter R.; Ruffet, Gilles; Leith, Leslie; Loseth, Helge; Rodrigues, Nuno; Leanza, Hector A.; Zanella, Alain

    2014-12-01

    Where the Neuquén Basin of Argentina abuts the Andes, hundreds of veins of solid hydrocarbon (bitumen) are visible at the surface. Many of these veins became mines, especially in the last century. By consensus, the bitumen has resulted from maturation of organic-rich shales, especially the Vaca Muerta Fm of Late Jurassic age, but also the Agrio Fm of Early Cretaceous age. To account for their maturation, recent authors have invoked regional subsidence, whereas early geologists invoked magmatic activity. During 12 field seasons (since 1998), we have tracked down the bitumen localities, mapped the veins and host rocks, sampled them, studied their compositions, and dated some of them. In the provinces of northern Neuquén and southernmost Mendoza, the bitumen veins are mostly sub-vertical dykes. They tend to be straight and continuous, crosscutting regional structures and strata of all ages, from Jurassic to Palaeocene. Most of the localities lie within 70 km of Tromen volcano, although four are along the Rio Colorado fault zone and another two are at the base of Auca Mahuida volcano. On both volcanic edifices, lavas are of late Pliocene to Pleistocene age. Although regionally many of the bitumen dykes tend to track the current direction of maximum horizontal tectonic stress (ENE), others do not. However, most of the dykes radiate outward from the volcanoes, especially Tromen. Thicknesses of dykes tend to be greatest close to Tromen and where the host rocks are the most resistant to fracturing. Many of the dykes occur in the exhumed hanging walls of deep thrusts, especially at the foot of Tromen. Here the bitumen is in places of high grade (impsonite), whereas further out it tends to be of medium grade (grahamite). A few bitumen dykes contain fragments of Vaca Muerta shale, so that we infer forceful expulsion of source rock. At Curacó Mine, some shale fragments contain bedding-parallel veins of fibrous calcite (beef) and these contain some bitumen, which is

  8. Dyke Swarms in Southeastern British Columbia: Mineralogical and Geochemical Evidence for Emplacement of Multiple Magma Types During Orogenic Collapse

    NASA Astrophysics Data System (ADS)

    Freeman, M.; Owen, J. P.; Hoskin, P. W.

    2009-05-01

    Eocene dyke swarms in southeastern British Columbia provide an important record of the tectonic and magmatic history of the Cordillera following orogenic collapse. New field mapping, petrographic, and geochemical data is presented for a swarm of more than thirty dykes located near the mining town of Trail, B.C. Detailed field mapping revealed that individual dykes are highly diverse, both in composition and morphology. As a group, the dykes trend northwest (average strike of 338 degrees) and dip steeply to the southwest. Their average thickness is approximately 1.5m, with a range from 4.5m to less than 1cm. Three sub-parallel dykes were mapped for a length of 2km, and exhibit irregularities in their form such as branching and offshoots that follow fractures in the country rock. Thin-section analysis shows a wide variety of rock types within the swarm, including: micro-quartz syenite, micro-syenite, micro-monzonite, latite, basalt, basaltic andesite, and lamprophyre. Texturally, these samples are consistently porphyritic and partially altered to chlorite and sericite. This alteration commonly occurs in concentric rims around phenocrysts. The samples are typically intergranular, although some display trachytic texture. Whole-rock geochemistry shows that the dykes have a wide range in composition, with SiO2 between 76.45 wt.% and 45.15 wt.% and MgO between 0.13 wt.% and 13.16 wt.%. The results also revealed that one dyke has very high values of Ni (430 ppm), Cr (1420 ppm), and Co (50 ppm), giving it a fairly primitive composition. Harker diagrams and trace element plots show three distinct groups: mafic calc-alkaline dykes, felsic calc- alkaline dykes, and minette lamprophyres. The felsic dykes are characterized by negative Eu and Sr anomalies suggesting fractionation of plagioclase feldspar, as well as pronounced negative P and Ti anomalies. The minettes are enriched in LILE and depleted in HSFE relative to the mafic dykes. The three groups do not appear to be

  9. Variscan potassic dyke magmatism of durbachitic affinity at the southern end of the Bohemian Massif (Lower Austria)

    NASA Astrophysics Data System (ADS)

    Zeitlhofer, Helga; Grasemann, Bernhard; Petrakakis, Konstantin

    2016-06-01

    Dykes in the Strudengau area (SW Moldanubian Zone, Austria) can be mineralogically divided into lamprophyres (spessartites and kersantites) and felsic dykes (granite porphyries, granitic dykes and pegmatoid dykes). Geochemical analyses of 11 lamprophyres and 7 felsic dykes show evidence of fractional crystallization. The lamprophyres are characterized by metaluminous compositions, intermediate SiO2 contents and high amounts of MgO and K2O; these rocks have high Ba (800-3000 ppm) and Sr (250-1000 ppm) contents as well as an enrichment of large-ion lithophile elements over high field strength elements, typical for enriched mantle sources with variable modifications due to fractionation and crustal contamination. This geochemical signature has been reported from durbachites (biotite- and K feldspar-rich mela-syenites particularly characteristic of the Variscan orogen in Central Europe). For most major elements, calculated fractionation trends from crystallization experiments of durbachites give an excellent match with the data from the Strudengau dykes. This suggests that the lamprophyres and felsic dykes were both products of fractional crystallization and subsequent magma mixing of durbachitic and leucogranitic melts. Rb-Sr geochronological data on biotite from five undeformed kersantites and a locally deformed granite porphyry gave cooling ages of c. 334-318 Ma, indicating synchronous intrusion of the dykes with the nearby outcropping Weinsberger granite (part of the South Bohemian Batholith, c. 330-310 Ma). Oriented matrix biotite separated from the locally deformed granite porphyry gave an Rb-Sr age of c. 318 Ma, interpreted as a deformation age during extensional tectonics. We propose a large-scale extensional regime at c. 320 Ma in the Strudengau area, accompanied by plutonism of fractionated magmas of syncollisional mantle-derived sources, mixed with crustal components. This geodynamic setting is comparable to other areas in the Variscan belt documenting an

  10. Eocene slab breakoff of Neotethys as suggested by dioritic dykes in the Gangdese magmatic belt, southern Tibet

    NASA Astrophysics Data System (ADS)

    Ma, Xuxuan; Xu, Zhiqin; Meert, Joseph G.

    2016-04-01

    The Gangdese magmatic belt in southern Tibet demarcates an important boundary between the Indian and Eurasian plates. Due to its location and magmatic evolutionary history, it is key to understanding both the history of Neotethys closure and the Indo-Asian collisional process. This study presents new geochronological and geochemical data for dioritic dykes in the southern Gangdese magmatic belt in southern Tibet. U-Pb geochronological results reveal that the dykes were emplaced at ca. 41 Ma and thus broadly coeval with the 40-38 Ma Dazi volcanics and the 42-40 Ma Gaoligong-Tengliang basaltic dykes. Geochemically, these dykes are characterized by alkaline signature, high Mg# (57-63) and low TiO2 contents (~ 0.9-1.0), showing notable enrichment of light rare earth elements relative to the heavy rare earth elements, enrichment of incompatible elements (i.e. Cs, Rb, Ba, Th and U), and depletion of high field strength elements (i.e. Nb, Ta and Ti). In addition, a large variation of zircon εHf(t) values (- 10 to + 13) was shown, implying heterogeneity of magma sources. A heterogeneous source is also suggested by the occurrence of xenocrysts in the dykes. These observations suggest that the magma source of the dykes was dominated by partial melting of lithospheric mantle and then subsequently contaminated by crustal material during ascent. In combination with other geological data in the region, we suspect that the slab slicing of the Neotethys played a key role in the formation of the lithospheric mantle-derived dioritic dykes and adakitic granite, asthenosphere-derived volcanics, basaltic dykes, as well as the recently reported strongly fractionated granites.

  11. Passive kimberlite intrusion into actively dilating dyke-fracture arrays: evidence from fibrous calcite veins and extensional fracture cleavage

    NASA Astrophysics Data System (ADS)

    Basson, I. J.; Viola, G.

    2004-09-01

    Calcite veins are invariably associated with en-echelon kimberlite dyke-fracture arrays. A detailed microstructural study of veining indicates four vein types. Type I stretched or ataxial veins are defined by high aspect ratio calcite fibers that are crystallographically continuous with calcite of the kimberlite matrix wall rock, by elongated phenocrystic phlogopite with sharp crystal terminations centered on contacts between adjacent calcite fibers and by phenocrystic phlogopite that grows or extends across these veins. Type I vein mineralogy indicates syn-dilational crystallization of vein minerals in local tensional areas within the kimberlite. Vein Types II (stretched to syntaxial elongate-blocky) and III (antitaxial) indicate late crystallization vein mineral growth during subsequent or repeated dilation. Calcite fibers in Type I to Type III veins are orthogonal to the contacts of their host dykes regardless of the orientation of vein margins. Type IV calcite veins, with blocky or mosaic/polycrystalline textures, are attributed to minor post-intrusion extension, which was potentially accompanied by repeated kimberlite intrusion within a given dyke array. Syn-crystallization/syn-intrusion Type I veins and an ubiquitous dyke-parallel fracture cleavage, in a zone up to 4 m on either side of dyke contacts, suggest that en-echelon kimberlite dyke-fracture arrays occupied the approximate center of zones of active dilation within the brittle carapace of the upper crust. Type II and III veins indicate that extension or dilation continued, independently of an occupying kimberlite fluid phase, after initial intrusion. Arrested mobile hydrofracturing, under low differential stress within the upper brittle or seismic carapace of the continental crust, followed by repeated dilation of the dyke-fracture system, is proposed as a mechanism for producing the features observed in this study. The conditions constrained in this study indicate passive dyke intrusion into dilating

  12. Geochronology, Geochemistry and Petrogenesis of the Intermediate and Acid Dykes in Linzhou Basin, Southern Tibet

    NASA Astrophysics Data System (ADS)

    Dong, M.; Zhao, Z.; Zhu, D. C.; Dong, G.; Mo, X.

    2015-12-01

    The Linzizong volcanic succession (also called Linzizong Group, ~65-45 Ma), which occurred in southern Gangdese magmatic belt in response to the collision processes between India and Eurasia continents, have been well studied in the Linzhou Basin, to the northeast of Lhasa. Our research obtains some new results of zircon U-Pb, Hf isotopic data, and whole rock major and trace elements geochemical data of the intermediate (diorite porphyry) to acid (granite porphyry) dykes intruded into the Linzizong volcanics in Linzhou Basin. These dykes intruded into Dianzhong and Nianbo formations of Linzizong Group. All the samples are sub-alkaline, varying from calc-alkaline to high-K calc-alkaline series. They are peraluminous (A/CNK>1.1). The diorite porphyry, intruded in 62.4Ma with positive zircon Hf isotopes (ɛHf(t)=+5.1~+7.6), have similar composition to the andesitic rocks from Dianzhong Formation. The granite porphyries, intruded between 55.1Ma and 61.1Ma, with ɛHf(t) ranging from -1.1 to +10.4, have comparable composition with the rhyolitic Nianbo Formation. A series of evidences, including: (1) the samples have positive, mantle-like Hf feature (average ɛHf(t)=+5.9 of 86 samples); (2) wide-range variation of ɛHf(t) in samples (3.5~8.8 ɛ units in the four granite porphyries), which implying an inhomogeneous source regions; (3) magma-mixing trend in the plots of FeOT against MgO, suggesting that the magma-mixing processes that have taken place in the southern Gangdese belt, can also be applied to explain the origin of these dykes in Linzhou Basin. The dykes intruded coeval or shortly later than their equivalent volcanic rocks (Dianzhong and Nianbo formations), are in the transitional settings from subduction of Tethyan oceanic crust to the collisional between India and Eurasia continents.

  13. The intensity of the geomagnetic field from 2.4 Ga old Indian dykes

    NASA Astrophysics Data System (ADS)

    Valet, Jean-Pierre; Besse, Jean; Kumar, Anil; Vadakke-Chanat, Sayoob; Philippe, Edouard

    2014-06-01

    paleomagnetic records from dyke swarms provide a unique source of information regarding the Archean geomagnetic field and more specifically the average field strength produced by the early dynamo. We sampled 16 paleomagnetic sites from the Dharwar giant dyke swarm in southern India which was emplaced between 2.365 and 2.368 Ga. Despite taking great care in selecting locations exempt of any geological disturbance, only two of these sites provided primary directions with very steep inclinations and therefore were emplaced in close to a magnetic pole. Paleointensity experiments were conducted on a subset of samples from the dyke margins. The characteristic magnetization is carried by single domain magnetite grains with a very narrow range of unblocking temperatures inferred from the sharp decrease by at least 75% of their remanence above 520°C. The paleointensity results indicate an average low field of 9.2 ± 7 µT, consistent with reported values from Canadian dyke swarms for the same period. These results combined with the Thellier-Thellier determinations obtained so far for the Precambrian suggest that a low field period prevailed from circa 2.3 to 1.8 Ga, while the preceding and following time intervals are characterized by significantly stronger paleointensities. Although this suite of episodes is not fully incompatible with previous models for the long-term evolution of the geodynamo, it is tempting to make the link with the recent suggestion of an early dynamo sustained within a conductive magma layer at the base of the mantle from 3.5 to 2.5 Ga which progressively declined until convection became sufficiently efficient to reactivate a strong dynamo process within the Earth's liquid core.

  14. Integrating WorldView-2 imagery and terrestrial LiDAR point clouds to extract dyke swarm geometry: Implications for magma emplacement mechanisms

    NASA Astrophysics Data System (ADS)

    Ni, Nina; Chen, Ninghua; Chen, Jianyu; Liu, Mingliang

    2016-01-01

    Dyke geometries are useful indicators of the palaeostress field during magma emplacement. In this paper, we present a multi-scale extraction method of dyke geometries by integrating WorldView-2 (WV2) imagery and terrestrial light detection and ranging (LiDAR) data. Color composite and fusion WV2 images with 0.5-m resolution were generated by using the Gramm-Schmidt Spectral Sharpening approach, which facilitates the discrimination of dyke swarms and provides the ability to measure the orientation, exposed length, and thickness of dykes in sub-horizontal topographic exposures. A terrestrial laser scanning survey was performed on a sub-vertical exposure of dykes to obtain LiDAR data with point spacing of ~ 0.02 m at 30 m. The LiDAR data were transformed to images for extracting dyke margins based on image segmentation, then the dyke attitudes, thicknesses, and irregularity of dyke margins were measured according to the points on dyke margins. This method was applied at Sijiao Island, Zhejiang, China where late Cretaceous mafic dyke swarms are widespread. The results show that integrating WV2 imagery and terrestrial LiDAR improves the accuracy, efficiency, and objectivity in determining dyke geometries in two and three dimensions. The ENE striking dykes are dominant, and intruded the host rock (mainly granite) with sub-vertical dips. Based on the aspect ratios of the dykes, the magmatic overpressure was estimated to be less than 11.5 MPa, corresponding to a magma chamber within 6.6 km in the lithosphere.

  15. Dyking Mechanism and Melting transfer, Misho granitoid Pluton (NW of Iran)

    NASA Astrophysics Data System (ADS)

    Mehri, M.; Mohssen, M.

    2009-04-01

    Misho granitoid pluton are exposed in NW of Misho elevation and SW of Marand depression (Nw of Iran). Mineralogical paragenesis of pluton contain unhedral to sub-hedral quartz, alkaline feldspar (microcline and sub-hedral to unhedral orthoclase), two type biotites, subhedral to euhedral plagioclase (oligoclase to albite), two type zircon, magmatic epidote, sphene and apatite. Pluton, samples show geochemical characteristic of syn - to post - collisional environment, s-type granite and allocktonous. Pluton located in faulted area with Paleozoic respect dating. Source rocks of Pluton are meta - graywake and meta - pelite mixed. One type of zircon and biotite are restitic. Pluton samples have textures that indicate the effect and evidence of pressure syn - crystallization. Field geological, mineralogical and geochemical characteristic of samples from this pluton associated with enclaves riched in mica and shapes of pluton suggest quick arising and dyking mechanism as main mechanism for melt transfer. This caused restitic zircon and biotite remained, there for main mechanism of arising and generation of this pluton are dyking with propagation of fractures so that diaprism process and mechanism have very low role and effect in emplacement and melt transfer of Misho granitoid. Key Words: Misho Pluton, Restitic biotite, Arising mechanism, Dyking

  16. Dyking Mechanism and Melting transfer, Misho granitoied Pluton (NW of Iran)

    NASA Astrophysics Data System (ADS)

    Mehri, M.; Mohssen, M.; Arezoo, S.; Aram, S.

    2009-04-01

    Misho granitoid pluton are exposed in NW of Misho elevation and SW of Marand depression (In Iran). Mineralogical paragenesis of pluton contain unhedral to sub â€" hedral quartz , alkaline feldspar (microcline and sub - hedral to unhedral orthoclase) , two type biotites , subhedral to euhedral plagioclase (oligoclase to albite) , two type zircon , magmatic epidote , sphene and apatite. Pluton ,s samples show geochemical charactrestic of syn â€" to post â€" collisional environment , s â€" type granite and allocktonous. Pluton located in faulted area with Paleozoic respect dating. Source rocks of Pluton are meta â€" graywake and meta â€" pelite mixed. One type of zircon and biotite are restitic. Pluton , s samples have textures that indicate the effect and evidence of pressure syn â€" crystallization. Field geological , mineralogical and geochemical characteristic of samples from this pluton associated with enclaves riched in mica and shapes of pluton suggest quick arising and dyking mechanism as main mechanism for melt transfer . this caused restitic zircon and biotite remained , There for main mechanism of arising and generation of this pluton are dyking with propagation of fractures so that diaprism process and mechanism have very low role and effect in emplacement and melt ,s transfer of Misho granitoid. Key Words: Misho Pluton , Restitic biotite , Arising mechanism , Dyking

  17. Formation of composite dykes by contact remelting and magma mingling: The Shaluta pluton, Transbaikalia (Russia)

    NASA Astrophysics Data System (ADS)

    Litvinovsky, B. A.; Zanvilevich, A. N.; Katzir, Y.

    2012-10-01

    A unique opportunity to study the source areas, from which composite dykes were injected, occurs in the Shaluta pluton, Transbaikalia, Russia. The major quartz syenite pluton was intruded by several synplutonic gabbro bodies of various sizes. Investigations of the contact zones between gabbro and host syenite showed that liquid basalt magma intruded the incompletely crystallized coarse-grained quartz syenite with T = 700-720 °C and caused contact remelting of the silicic rock at about 900-950 °C. Mechanical interaction between newly formed silicic melt and partially crystallized mafic magma resulted in extensive magma mingling. Chemical interaction was exhibited by migration of MgO, CaO, FeO∗, Sr, H2O and Cl from the basalt magma, whereas silica, alkalis, Rb and Ba migrated from the silicic refusion zone into the crystallized gabbro. Presence of melt inclusions with homogenization temperature ranging from 640 to 790 °C in quartz and attaining 850-900 °C in late clinopyroxene indicates that at least part of newly formed minerals crystallized from the hybrid melt. Mingled magmatic material was squeezed out inwards, into the host solid quartz syenite pluton and formed dyke-like apophyses that can be traced for a distance of 60-70 m from the contact zone. Apophyses have the same dimensions, structure and composition as typical composite dykes that are common in the roof pendant over the gabbro bodies and nearby the gabbro exposures.

  18. The influence of inherited structures on dyke emplacement during Gondwana break-up in southwestern Africa

    NASA Astrophysics Data System (ADS)

    Will, Thomas; Frimmel, Hartwig

    2013-04-01

    A kinematic analysis of Cretaceous and pre-Cretaceous faulting and fracturing was carried out along the west coast of Southern Africa extending from the greater Cape Town area to the Orange River and beyond into southern Namibia. This study was augmented by the geometric analysis of mainly Cretaceous mafic dykes exposed from SW Angola to the southern tip of Africa. The kinematic analysis shows that the Cretaceous rifting event that led to the opening of the modern South Atlantic was largely controlled by NW-SE and NE-SW-striking structures. In the coastal areas of South Africa the Cretaceous deformation was dominated by NE-SW extension, whereas a general E-W-oriented extension prevailed further north. Analysis of reverse and strike-slip faulting in the Gariep and western Saldania Belts shows that the Pan-African constrictional deformation in South Africa was mainly controlled by ENE-WSW- to ESE-WNW-oriented shortening. Further north, the geometry of the Odgen Rock Mylonites in Namibia is controlled by N-S-striking strike-slip faults. The geometric analysis of the orientation of the mafic dykes also points to an E-W-oriented extension direction in the coastal areas extending from southern Angola to Meob and Conception Bay in west-central Namiba and changes to a generally NE-SW-oriented extension along the west coast of South Africa. Further inland in the Damara Belt sensu strictu, the geometric analysis of dykes belonging to the Hentjes Bay-Outjo Dyke Swarm also indicates NE-SW-oriented extension but, in addition, also a strong component of NW-SE-directed extension controlled dyke emplacement. The results of this study suggest that Pan-African (or older) structural discontinuities were re-utilised during the opening of the South Atlantic in the Early Cretaceous. The extension directions associated with Cretaceous Gondwana break-up structures are subparallel to the Pan-African shortening orientations. The inherited structural anisotropies are generally parallel to

  19. The Central Atlantic Magmatic Province: Age Comparison Between the South Carolina Dykes and Morocco Lava Flows

    NASA Astrophysics Data System (ADS)

    Youbi, N.; Nomade, S.; Breutel, E.; Knight, K.

    2003-12-01

    Believed to be the largest volcanic province on Earth at more than 6000 km long and 2000 km wide, the Central Atlantic Magmatic Province (CAMP) stretches from Eastern Canada to Brazil and from Western Spain to the Ivory Coast. Due to the massive erosion and subsequent in filling of these areas since the 200 Ma rifting event, dikes and sills constitute the majority of the exposed CAMP volcanics. However, well preserved lava flows have been found in the Triassic basins of the Northeastern United States and Morocco. Despite numerous 40Ar/39Ar dating attempts, very few of the exposed CAMP volcanics have been successfully dated due to a variety of factors including; excess argon and alteration. Especially no age is available in the well-mapped but structurally complex South and North Carolina dykes swarm as well as only few scattered ages in the Moroccan Trias-Liassic basins. Our goal is to better constrain the emplacement timing of the dykes swarm but also to compare age of both intrusive and effusive rocks from the same magmatic event but separated from more than 1000 km, 200 Mys ago. Several questions continue to surround the CAMP volcanic province including its cause and emplacement mechanism. Toward that end we have collected and dated dyke samples from the Carolinas and flows in Morocco, 1000 km away and across the rift. We anticipate that a comparison of these dates will enable us to understand more about the timing between the emplacement of the flows and dykes. We have collected in South Carolina and High Atlas in Morocco 7 and 9 hand samples respectively. Specimens from South Carolina correspond to the three distinct dykes' direction NE-SW, NW-SE and NS. In Morocco, samples were collected in four sections (100 to 300 m thick) located in the High Atlas between Marrakech and Ouarzazate. From each hand sample two different transparent plagioclase fractions, 250-180 and 180 to 100 microns, were separated. We have performed step heating experiments at the Berkeley

  20. Distribution of petroleum hydrocarbons and toluene biodegradation, Knox Street fire pits, Fort Bragg, North Carolina

    USGS Publications Warehouse

    Harden, S.L.; Landmeyer, J.E.

    1996-01-01

    An investigation was conducted at the Knox Street fire pits, Fort Bragg, North Carolina, to monitor the distribution of toluene, ethylbenzene, and xylene (TEX) in soil vapor, ground water, and ground-water/vapor to evaluate if total concentrations of TEX at the site are decreasing with time, and to quantify biodegradation rates of toluene in the unsaturated and saturated zones. Soil-vapor and ground-water samples were collected around the fire pits and ground-water/vapor samples were collected along the ground-water discharge zone, Beaver Creek, on a monthly basis from June 1994 through June 1995. Concentrations of TEX compounds in these samples were determined with a field gas chro- matograph. Laboratory experiments were performed on aquifer sediment samples to measure rates of toluene biodegradation by in situ micro- organisms. Based on field gas chromatographic analytical results, contamination levels of TEX compounds in both soil vapor and ground water appear to decrease downgradient of the fire-pit source area. During the 1-year study period, the observed temporal and spatial trends in soil vapor TEX concentrations appear to reflect differences in the distribution of TEX among solid, aqueous, and gaseous phases within fuel-contaminated soils in the unsaturated zone. Soil temperature and soil moisture are two important factors which influence the distribution of TEX com- pounds among the different phases. Because of the short period of data collection, it was not possible to distinguish between seasonal fluc- tuations in soil vapor TEX concentrations and an overall net decrease in TEX concentrations at the study site. No seasonal trend was observed in total TEX concentrations for ground- water samples collected at the study site. Although the analytical results could not be used to determine if ground-water TEX concen- trations decreased during the study at a specific location, the data were used to examine rate constants of toluene biodegradation. Based on

  1. Palaeoproterozoic Indian shield in the global continental assembly: Evidence from the palaeomagnetism of mafic dyke swarms

    NASA Astrophysics Data System (ADS)

    Radhakrishna, T.; Krishnendu, N. R.; Balasubramonian, G.

    2013-11-01

    Palaeomagnetic study of Palaeoproterozoic mafic dykes in the basement along the margins of the Cuddapah basin, the largest Precambrian sedimentary basin in south India, is presented in detail for a general discussion of Palaeoproterozoic igneous activity in India. The results are compared with all earlier published data on mafic dykes in India and are integrated with recently-published high-precision U-Pb baddeleyite ages to provide a comprehensive account of Palaeoproterozoic igneous activity in India. The analysis consolidates palaeomagnetic poles for six age divisions between 2.45 and 1.85 Ga with robust statistical criteria. Our best estimates of overall mean poles from 241 dykes are situated at (1) λ = 17.7°N; Φ = 106.0°E (A95 = 9.0°; 7N = 24) at c. 2.45 Ga, (2) λ = 7.1°N; Φ = 57.2°E (A95 = 4.5°; N = 69) at c. 2.37 Ga, (3) λ = 41.6°S; Φ = 5.5°E (A95 = 5.1°; N = 34) at c. 2.22 Ga, (4) λ = 4.7°N; Φ = 343.0°E (A95 = 4.4°; N = 31) at 2.18 Ga, (5) λ = 49.2°N; Φ = 332.9°E (A95 = 4.8°; N = 24) at 1.99-1.89 Ga and (6) λ = 73.7°N; Φ = 282.6°E (A95 = 2.9°; N = 39) at 1.86 Ga. The data permit us to construct an apparent polar wander path for the Indian shield for an ~ 600 Ma interval of the Palaeoproterozoic eon (2.45-1.85 Ga). Testing and evaluation of continental reconstructions for this interval, which are mostly based on geological correlations, reveal many inconsistencies. Between 2.45 and 2.37 Ga, the Indian shield was situated at higher latitudes similar to the Yilgarn craton of Australia. It was subsequently located near the equator at 2.22, 2.18, 1.99 and 1.86 Ga. Thus, an India-Australia connection is supported during these times, but a proposed Australia-Kaapvaal link in "Zimvaalbara" and a Dharwar (India)-Slave connection in "Sclavia" or a Superior-Zimbabwe-India connection in "Superia" are inconsistent with Indian data. In addition, the close palaeomagnetic comparison between the Palaeoproterozoic dykes of Dharwar

  2. Post-Knox Ordovician stratigraphic sequences and the significance of the Rocklandian K-bentonites, eastern United States

    SciTech Connect

    Haynes, J.T. . Dept. of Geography and Earth Science)

    1992-01-01

    The depositional sequences of the post-Knox Ordovician are reinterpreted and summarized, with emphasis on the stratigraphic importance of the Rocklandian K-bentonites relative to the various sequence-defining unconformities associated with them. The Deicke and Millbrig K-bentonite Beds can be traced through the subsurface to Cincinnati Arch exposures, where a remarkably similar stratigraphy occurs; fenestral micrites (Tyrone/Carters Fms.) unconformably underlie fossil-rich limestone (Lexington/Hermitage Fms.). The Deicke and Millbrig, however, both occur in the fenestral micrites below the unconformity, rather than above it, a stratigraphy which suggests that if this post-Tyrone unconformity is the same as the post-Quimbys Mill unconformity, it is a diachronous surface, climbing upsection and crossing the K-bentonites southeast of the Upper Mississippi Valley. In eastern belts two lesser unconformities are associated with the K-bentonites. Locally in Birmingham, AL, a post-Chickamauga unconformity is 4 m above the Millbrig and is overlain by a thin Sequatchie Fm., itself unconformably overlain by the Silurian Red Mountain Fm. In VA between Roanoke and Wytheville on the Pulaski and Cove Mountain thrust sheets, the Deicke is absent and a sub-Bays unconformity exists where the Walker Mountain Sandstone, a pebbly quartz arenite 18--28 m below the Millbrig, overlies Black River limestones. The post-Tyrone unconformity, like the older post-Knox unconformity, is a regionally extensive hiatus, suggestive of a eustatic sea-level change. By contrast, the unconformities that are restricted to only the eastern Valley and Ridge may be evidence of tectonism along the continental margin during the ordovician. Similarly localized unconformities are recognized in Silurian and Devonian strata as well throughout the southern Appalachians.

  3. Early Jurassic mafic dykes from the Xiazhuang ore district (South China): Implications for tectonic evolution and uranium metallogenesis

    NASA Astrophysics Data System (ADS)

    Wang, Lian-Xun; Ma, Chang-Qian; Lai, Zhong-Xin; Marks, Michael A. W.; Zhang, Chao; Zhong, Yu-Fang

    2015-12-01

    A comprehensive study on zircon U-Pb age dating, whole-rock geochemistry and Sr-Nd isotope data has been conducted on the mafic rocks of the Xiazhuang uranium ore district and adjacent regions in South China. Based on field work and petrographic features, three rock types (the Kuzhukeng gabbro, the WNW-trending dolerite dykes and the NNE-trending lamprophyre dykes) are distinguished. Early Jurassic SHRIMP and LA-ICPMS ages of zircon for the Kuzhukeng gabbro (198 ± 1 Ma) and WNW-trending dolerite dykes (193 ± 4 Ma) have been obtained, which are 50 Ma older than previously thought (being Cretaceous). These geochronologic data provide new evidence for the rarely identified Early Jurassic magmatisms in South China. Whole-rock geochemical data for the Kuzhukeng gabbro and WNW-trending dolerite dykes are similar, both of which being higher in FeO and TiO2 but lower in SiO2 and K2O than the NNE-trending lamprophyre dykes. Trace element characteristics and Sr-Nd isotope data indicate arc-like signatures similar to the Cretaceous southeast coast basalts of China for the lamprophyre dykes, but an OIB-like geochemical affinity for the high-TiO2 mafic rocks similar to the Permo/Triassic Emeishan flood basalts and the Middle Jurassic Ningyuan alkaline basalts. We propose that the lamprophyre dykes formed in an arc volcanic system driven by the subduction of the paleo-Pacific plate. In contrast, the Kuzhukeng gabbro and associated dolerite dykes record the post-orogenic (Indosinian) extension event in the Tethyan tectonic regime. This further implies that the Indosinian extension may have lasted until the Early Jurassic, and therefore, the subduction of the paleo-Pacific plate in south China was probably later than this period. Most U deposits of the Xiazhuang area are located at the intersection between the WNW-trending dolerite dykes and the NNE-trending faults within the Triassic granites of eastern Guidong complex, South China. Previous metallogenesis studies assumed that

  4. Late Cretaceous dacitic dykes swarm from Central Iran, a trace for amphibolite melting in a subduction zone

    NASA Astrophysics Data System (ADS)

    Nosouhian, N.; Torabi, G.; Arai, S.

    2016-05-01

    Late Cretaceous Bayazeh dyke swarm is situated in the western part of the Central-East Iranian Microcontinent (CEIM). These dykes with a dominant northeast-southwest trend occur in the Eastern margin of the Yazd block. They cross cut the Lower Cretaceous sedimentary rocks. The length of the Bayazeh dykes occasionally reaches up to the 2 km. Rock forming minerals of these dykes are plagioclase (andesine and oligoclase), amphibole (magnesio-hastingsitic hornblende, magnesio-hornblende and tschermakitic hornblende), quartz, K-feldspar (orthoclase), zircon and apatite. Secondary minerals are chlorite (pycnochlorite), albite, magnetite and calcite. The main textures are porphyritic, glomeroporphyritic and poikilitic. The felsic character of the Bayazeh dacitic dykes is shown by their high SiO2 (62.70 to 64.60 wt %) and low [Fe2O3* + MgO + MnO + TiO2] (average 4.64 wt %) contents. These dykes represent the peraluminous to metaluminous nature and their Na2O and K2O values are 5.20-7.14 and 1.51-2.59 wt %, respectively, which reveal their sodic chemistry. The trace element characteristics are the LREE enrichment relative to HREE, [La/Yb]CN = 13.27-22.99, and slightly negative or positive Eu anomaly. These geochemical characteristics associated with low Nb/La (0.16-0.25), Yb/Nd (0.04-0.05) and high Zr/Sm (37.60-58.25) ratios indicate that the melting of a metamorphosed subducted oceanic crust is occurred where the residual mineral assemblage is dominated by garnet amphibolite. The chemical compositions of the Bayazeh dykes resemble those of slab-derived tonalite-trondhjemite-granodiorite (TTG) series. They were formed by subduction of Mesozoic Neo-Tethys -related Nain and Ashin oceanic crusts.

  5. Van der Waals Forces

    NASA Astrophysics Data System (ADS)

    Parsegian, V. Adrian

    2006-03-01

    This should prove to be the definitive work explaining van der Waals forces, how to calculate them and take account of their impact under any circumstances and conditions. These weak intermolecular forces are of truly pervasive impact, and biologists, chemists, physicists and engineers will profit greatly from the thorough grounding in these fundamental forces that this book offers. Parsegian has organized his book at three successive levels of mathematical sophistication, to satisfy the needs and interests of readers at all levels of preparation. The Prelude and Level 1 are intended to give everyone an overview in words and pictures of the modern theory of van der Waals forces. Level 2 gives the formulae and a wide range of algorithms to let readers compute the van der Waals forces under virtually any physical or physiological conditions. Level 3 offers a rigorous basic formulation of the theory. Author is among the most highly respected biophysicists Van der Waals forces are significant for a wide range of questions and problems in the life sciences, chemistry, physics, and engineering, ranging up to the macro level No other book that develops the subject vigorously, and this book also makes the subject intuitively accessible to students who had not previously been mathematically sophisticated enough to calculate them

  6. Pythagoras Meets Van Hiele.

    ERIC Educational Resources Information Center

    Flores, Alfinio

    1993-01-01

    Develops the Pythagorean Theorem in the context of the Van Hiele levels by presenting activities appropriate for each level. Activities point to preparatory development (level 0), give 3 different versions of Euclid's proof (levels 1, 2, and 3), give some generalizations of the theorem (level 3), and explore the Pythagorean relationship in other…

  7. Van Gogh's Sunflowers

    ERIC Educational Resources Information Center

    Daddino, Michelle

    2010-01-01

    In this article, the author describes an art project wherein kindergarten students painted sunflowers. These beautiful and colorful sunflowers were inspired by the book "Camille and the Sunflowers" by Laurence Anholt, which does an amazing job of introducing young children to the art and life of Vincent van Gogh.

  8. Magma-maintained rift segmentation at continental rupture in the 2005 Afar dyking episode.

    PubMed

    Wright, Tim J; Ebinger, Cindy; Biggs, Juliet; Ayele, Atalay; Yirgu, Gezahegn; Keir, Derek; Stork, Anna

    2006-07-20

    Seafloor spreading centres show a regular along-axis segmentation thought to be produced by a segmented magma supply in the passively upwelling mantle. On the other hand, continental rifts are segmented by large offset normal faults, and many lack magmatism. It is unclear how, when and where the ubiquitous segmented melt zones are emplaced during the continental rupture process. Between 14 September and 4 October 2005, 163 earthquakes (magnitudes greater than 3.9) and a volcanic eruption occurred within the approximately 60-km-long Dabbahu magmatic segment of the Afar rift, a nascent seafloor spreading centre in stretched continental lithosphere. Here we present a three-dimensional deformation field for the Dabbahu rifting episode derived from satellite radar data, which shows that the entire segment ruptured, making it the largest to have occurred on land in the era of satellite geodesy. Simple elastic modelling shows that the magmatic segment opened by up to 8 m, yet seismic rupture can account for only 8 per cent of the observed deformation. Magma was injected along a dyke between depths of 2 and 9 km, corresponding to a total intrusion volume of approximately 2.5 km3. Much of the magma appears to have originated from shallow chambers beneath Dabbahu and Gabho volcanoes at the northern end of the segment, where an explosive fissural eruption occurred on 26 September 2005. Although comparable in magnitude to the ten year (1975-84) Krafla events in Iceland, seismic data suggest that most of the Dabbahu dyke intrusion occurred in less than a week. Thus, magma intrusion via dyking, rather than segmented normal faulting, maintains and probably initiated the along-axis segmentation along this sector of the Nubia-Arabia plate boundary. PMID:16855588

  9. Fracture mode analysis and related surface deformation during dyke intrusion: Results from 2D experimental modelling

    NASA Astrophysics Data System (ADS)

    Abdelmalak, M.; Mourgues, R.; Bureau, D.

    2012-04-01

    The analysis of surface deformation in response to approaching intrusion is important for assessing volcanic hazards. In this paper, we present results from 2D scaled models of magma intrusion, in which we discuss the propagation mode and related surface deformation during dyke growth. Our experiments consist in the injection of analogue magma (Golden syrup) into cohesive fine-grained silica powder, simulating the brittle upper crust. Using an optical image correlation technique (Particle Imaging Velocimetry), we were able to follow the surface deformation, the displacements within the country rock and to calculate strains induced by the magma emplacement. We identified two kinds of intrusion morphologies resulting from different interactions between the dyke and plastic deformations occurring in the country rock near the surface. In both morphologies, the dyke is vertical at depth. Our analysis demonstrates that both hydraulic tensile opening and shear-related propagation operate during this first stage of vertical growth. At the same time, the surface lifted up and formed a smooth symmetrical dome. Both types of morphologies differ in the upper part. During a second stage of evolution, the first type of intrusion inclined at a dip between 45 to 65°. This inclination is not caused by shear deformations and is attributed to stress rotation near the tip. Closer to the surface, the growth of the inclined sheet creates shear bands which conduct the fluid toward the surface. The surface uplift becomes asymmetric. The second type of intrusion does not rotate at depth and continues its vertical propagation by catching vertical tensile cracks. The intrusion of magma in these cracks creates horizontal stresses which are responsible for the closure of fractures and the formation of reverse faults. At the surface the dome remains symmetrical. For both intrusions, the surface uplift accelerates during the second stage and it is strongly influenced by the presence or the

  10. Fault and dyke detectability in high resolution seismic surveys for coal: a view from numerical modelling*

    NASA Astrophysics Data System (ADS)

    Zhou, Binzhong 13Hatherly, Peter

    2014-10-01

    Modern underground coal mining requires certainty about geological faults, dykes and other structural features. Faults with throws of even just a few metres can create safety issues and lead to costly delays in mine production. In this paper, we use numerical modelling in an ideal, noise-free environment with homogeneous layering to investigate the detectability of small faults by seismic reflection surveying. If the layering is horizontal, faults with throws of 1/8 of the wavelength should be detectable in a 2D survey. In a coal mining setting where the seismic velocity of the overburden ranges from 3000 m/s to 4000 m/s and the dominant seismic frequency is ~100 Hz, this corresponds to a fault with a throw of 4-5 m. However, if the layers are dipping or folded, the faults may be more difficult to detect, especially when their throws oppose the trend of the background structure. In the case of 3D seismic surveying we suggest that faults with throws as small as 1/16 of wavelength (2-2.5 m) can be detectable because of the benefits offered by computer-aided horizon identification and the improved spatial coherence in 3D seismic surveys. With dykes, we find that Berkhout's definition of the Fresnel zone is more consistent with actual experience. At a depth of 500 m, which is typically encountered in coal mining, and a 100 Hz dominant seismic frequency, dykes less than 8 m in width are undetectable, even after migration.

  11. Quantitative analogue modelling of the surface deformation associated with cone-sheet and dyke emplacement

    NASA Astrophysics Data System (ADS)

    Guldstrand, Frank; Bjugger, Fanny; Galland, Olivier; Burchardt, Steffi; Hallot, Erwan

    2014-05-01

    Inclined cone-sheets and sub-vertical dykes constitute the two principal types of magmatic sheet intrusions produced by volcanic systems. In active volcanic systems, the emplacement of sheet intrusions causes measurable surface deformation, which is analyzed through geodetic models. Geodetic model output is classically the shape of underlying intrusions causing the surface deformation, however, the results of these models are not testable as the subsurface intrusion is not accessible. Such test would only be doable with a physical system in which both (1) the surface deformation pattern and (2) the 3D shape of the underlying intrusion are known. In addition, established geodetic models only consider static magma intrusions, and do not account for emplacement and propagation processes. This would require combined good time- and space-resolution, which is not achievable with classical geodetic monitoring systems. We present a series of analogue models that may be a way of accurately linking surface deformation to the underlying intrusions and associated emplacement processes. We systematically varied depth of intrusion, the cohesive properties of the silica powder representing the country rock and the velocity of injected magma. The pressure of the intruding vegetable oil was measured through time, and the model surface topography was monitored. The low viscosity magma was simulated by molten vegetable oil, which solidified after intrusion; the solidified intrusion was then excavated and its shape was measured. By linking the development of the surface uplift in height, area, and volume with the pressure data from the onset of intrusion until the time of eruption, we identify characteristic laws of surface deformation. First results indicate that the pattern of uplift over time varies, depending on whether deformation is caused by a dyke- or a cone-sheet-shaped intrusion. The results from all experiments may enable us to distinguish the two intrusion types using

  12. Les dykes basiques du massif ancien de l'Ourika (Atlas de Marrakech, Maroc): géochimie et significationThe basic dykes of the Ourika old massif (High Atlas of Marrakech): Geochemistry and significance

    NASA Astrophysics Data System (ADS)

    Barakat, Ahmed; Marignac, Christian; Bouabdelli, Mohamed

    The Precambrian massif of Ourika is crosscut by two systems of basic dykes, striking N40°E and N90-120°E. Using incompatible trace elements, the two systems form two distinct chemical groups, displaying a continental tholeiitic affinity. The composition variations between the two defined groups can be due to heterogeneities of mantle sources and to contamination, during the magma ascent, by the continental crust. The emplacement of these basic dykes, before the late-PIII formations, can be related to the Neoproterozoic distension generalised to the Anti-Atlas chain. To cite this article: A. Barakat et al., C. R. Geoscience 334 (2002) 827-833.

  13. Regulation of Compound Leaf Development in Medicago truncatula by Fused Compound Leaf1, a Class M KNOX Gene[C][W

    PubMed Central

    Peng, Jianling; Yu, Jianbin; Wang, Hongliang; Guo, Yingqing; Li, Guangming; Bai, Guihua; Chen, Rujin

    2011-01-01

    Medicago truncatula is a legume species belonging to the inverted repeat lacking clade (IRLC) with trifoliolate compound leaves. However, the regulatory mechanisms underlying development of trifoliolate leaves in legumes remain largely unknown. Here, we report isolation and characterization of fused compound leaf1 (fcl1) mutants of M. truncatula. Phenotypic analysis suggests that FCL1 plays a positive role in boundary separation and proximal-distal axis development of compound leaves. Map-based cloning indicates that FCL1 encodes a class M KNOX protein that harbors the MEINOX domain but lacks the homeodomain. Yeast two-hybrid assays show that FCL1 interacts with a subset of Arabidopsis thaliana BEL1-like proteins with slightly different substrate specificities from the Arabidopsis homolog KNATM-B. Double mutant analyses with M. truncatula single leaflet1 (sgl1) and palmate-like pentafoliata1 (palm1) leaf mutants show that fcl1 is epistatic to palm1 and sgl1 is epistatic to fcl1 in terms of leaf complexity and that SGL1 and FCL1 act additively and are required for petiole development. Previous studies have shown that the canonical KNOX proteins are not involved in compound leaf development in IRLC legumes. The identification of FCL1 supports the role of a truncated KNOX protein in compound leaf development in M. truncatula. PMID:22080596

  14. Carbonate dykes associated with Arch˦an lode-Au mineralisation, Barberton greenstone belt, South Africa

    NASA Astrophysics Data System (ADS)

    Schürmann, L. W.; Ward, J. H. W.; Horstmann, U. E.; Jordaan, L. J.; Eaton, B.

    2000-02-01

    Carbonate dykes, exposed within the Barberton greenstone belt, display geochemical signatures similar to altered carbonatite. The trace element signature normalised to primordial mantle, and the chondrite-normalised REE trends of the Ulundi Dyke display geochemical similarities to carbonatites. In addition, stable isotope results from the Ulundi Dyke (δ13Cwhole rock and δ18Owhole rock range from -3.7 to -4.9‰ and 12.8 to 13.2‰, respectively) are similar to values found for samples of wall rock and vein carbonate from Arch˦an Au-quartz-carbonate-sulphide vein systems studied in the Barberton greenstone belt. Although the data do not plot in the field of primary igneous carbonatite, they are similar to data of deuterically-altered carbonatite. These associations strengthen the deduction that Iode-Au mineralised fractures and shear zones in the Barberton greenstone belt were open to mantle-tapping fundamental faults.

  15. AMS significance of dykes and granite from a same pluton - An example from the French Massif Central

    NASA Astrophysics Data System (ADS)

    Talbot, J.-Y.; Chen, Y.; Faure, M.

    2003-04-01

    The relationships between plutons and dykes of granite have been the topic of many studies since the hypothesis of "dyke propagation" was proposed as the main mode of ascent and emplacement of granitic plutons. However, most of observed pluton-related dykes can not be interpreted as "feeder dykes" but are fed by the magma chamber. Nevertheless, few AMS studies were carried out in both a pluton and its associated dykes to evaluate their internal fabrics. In the Cévennes area (SE of the French Massif Central), the Aigoual -- Saint-Guiral -- Liron granitic pluton consists of two cogenetic granitic facies. The main body is a porphyritic granodiorite facies which is common in the plutons of the Cévennes area. In the northern part of the pluton, a dyke swarm develops in the continuation of the porphyritic facies. Those NE-SW-trending dykes are composed of microgranite with locally porphyritic texture. This pluton intrudes metamorphic units dated at ca. 340--330 Ma and related to a N-S-trending shortening event. The emplacement of the pluton dated at ca. 310 Ma occured during the late-orogenic extension of the Hercynian belt. This extension is characterized by an E-W to NW-SE-trending stretching. An AMS study was carried out on the two granitic facies of this pluton. As shown by surveys of magnetic mineralogy, such as thermomagnetism, hysteresis loops, bulk magnetic susceptibility measurements, microscopic observations, the paramagnetic minerals, that is biotite with amphibole in traces, are the main carriers of the AMS for the two facies. Microstructures indicate the lack of significant solid-state deformation in both facies suggesting that AMS fabric is of magmatic origin and that no deformation is recorded after the complete crystallisation of the magma. In the porphyritic facies, the AMS fabric pattern is characterized by an E-W to NW-SE-trending lineation with shallow or moderate plunges mainly eastward. In general, magnetic foliations dip moderately eastward. This

  16. New U-Pb ages from dykes cross-cutting the Demirci metamorphics, NW Turkey: Implications for multiple orogenic events

    NASA Astrophysics Data System (ADS)

    Sen, Fatih; Koral, Hayrettin; Peytcheva, Irena

    2016-04-01

    A high-grade metamorphic sequence in the Sünnice Mountains, Bolu, NW Turkey, is represented by migmatitic quartzo-feldspathic gneisses in amphibolite facies called the Demirci metamorphics/paragneisses, and a sequence of low-grade meta-volcanics containing meta-andesites with minor meta-rhyolites and meta-sedimentary rocks called the Yellice meta-volcanics. They are intruded by the Dirgine granite with an age of Upper Ediacaran (576-565 Ma) and are considered a part of the İstanbul-Zonguldak Tectonic Unit. The Demirci paragneisses are also intruded by a number of dykes in various directions, traditionally considered without radiometric dating to have been emplaced in a single magmatic phase in the Eocene related to post-collision regime of the Anatolide-Tauride platform. Mafic-intermediate-felsic dykes cross-cutting the Demirci paragneisses have been investigated in maps of 1/1000 scale, and their U-Pb zircon age, major-trace element and kinematic data have been obtained. The mafics dykes cross-cutting the Yellice meta-volcanics, equivalents of those in the Demirci paragneisses, occur in N400-500E orientations and have calc-alkaline basalt compositions with a subduction signature. The intermediate dykes occur in N650W, N800W orientations and have calc-alkaline basaltic andesite to andesitic compositions with a subduction signature. Some felsics occur in N150W and N800E orientations and have calc-alkaline dacitic compositions with a collisional tectonic setting. Other calc-alkaline granitic dykes occur in N750E orientation and calc-alkaline granitic compositions with a subduction signature. U-Pb LA-ICP-MS dating of zircons yield ages from 485.7±3.6 Ma (i.e. Cambro-Ordovician) for N800E trending dacite dykes; 443.0±5.4 Ma (i.e. Ordovician-Silurian) for N150W trending dacite dykes; 301.0±1.6 Ma (i.e. Upper Pennsylvanian-Carboniferous) for N650W trending basaltic andesite dykes; 268.2±2.4 Ma (i.e. Guadalupian-Permian) for N40-500E trending basalt dykes; 262.9±3

  17. Magma storage and evolution in the Henties Bay-Outjo dyke swarm, Namibia -feeder systems of the Etendeka lavas

    NASA Astrophysics Data System (ADS)

    Keiding, J. K.; Frei, O.; Renno, A.; Veksler, I. V.; Trumbull, R. B.

    2012-04-01

    At the roots of continental flood basalts in the Paraná-Etendeka province are mafic dyke swarms that cover areas of several hundred kilometers. Studies of these dykes have focused mainly on the age, paleomagnetic properties and geochemistry, but less on pressure (P) and temperature (T) conditions of emplacement. However, the P and T conditions under which dyke magmas are stored are crucial for models of magma plumbing systems in flood basalt provinces. The erupted lavas are typically far from primitive compositions and generally show evidence for strong crustal assimilation in addition to magma fractionation. Unknown is where this magma modification took place in the crust. This is the kind of information that dyke studies can provide. The Henties Bay Outjo dyke swarm (HOD) in NW Namibia is the subject of this study. This is inarguably the best exposed of major dyke swarms associated with South Atlantic rifting and breakup and its geochemical diversity is well documented but aspects relating to the magma dynamics in the dyke swarm have not been studied before. Our approach is to use geochemical data from selected dykes to assess the differentiation and assimilation history of the magmas, and combine that with petrologic constraints on the temperature-pressure conditions of crystallization derived from mineral-melt equilibria. We have determined P-T estimates from olivine-melt and clinopyroxene-melt equilibria using analysis of phenocrysts by electron microprobe and applying the thermodynamic relations from Putirka (2008), who considered the standard error to be 1.7 kbar and 30°C. The calculations reflect only mineral-melt (proxied by whole-rock) compositions that are consistent with equilibrium. Crystallization temperatures range from 1040°C to 1350°C with a mean (n=58) of 1170 °C. These T-variations are not random, the high-temperature results come from a specific region of dyke emplacement but the reason for this is not yet clear. Olivine-melt temperatures

  18. Satellite-based observations of unexpected coastal changes due to the Saemangeum Dyke construction, Korea.

    PubMed

    Lee, Yoon-Kyung; Ryu, Joo-Hyung; Choi, Jong-Kuk; Lee, Seok; Woo, Han-Jun

    2015-08-15

    Spatial and temporal changes around an area of conventional coastal engineering can be easily observed from field surveys because of the clear cause-and-effect observable in the before and after stages of the project. However, it is more difficult to determine environmental changes in the vicinity of tidal flats and coastal areas that are a considerable distance from the project. To identify any unexpected environmental impacts of the construction of Saemangeum Dyke in the area, we examined morphological changes identified by satellite-based observations through a field survey on Gomso Bay tidal flats (15km from Saemangeum Dyke), and changes in the suspended sediment distribution identified by satellite-based observations through a hydrodynamic analysis in the Saemangeum and Gomso coastal area. We argue that hydrodynamic changes due to conventional coastal engineering can affect the sedimentation pattern in the vicinity of tidal flats. We suggest that the environmental impact assessment conducted before a conventional coastal engineering project should include a larger area than is currently considered. PMID:26104827

  19. Broad accommodation of rift-related extension recorded by dyke intrusion in Saudi Arabia

    USGS Publications Warehouse

    Pallister, J.S.; McCausland, W.A.; Jonsson, Sigurjon; Lu, Zhiming; Zahran, H.M.; El, Hadidy S.; Aburukbah, A.; Stewart, I.C.F.; Lundgren, P.R.; White, R.A.; Moufti, M.R.H.

    2010-01-01

    The extensive harrat lava province of Arabia formed during the past 30 million years in response to Red Sea rifting and mantle upwelling. The area was regarded as seismically quiet, but between April and June 2009 a swarm of more than 30,000 earthquakes struck one of the lava fields in the province, Harrat Lunayyir, northwest Saudi Arabia. Concerned that larger damaging earthquakes might occur, the Saudi Arabian government evacuated 40,000 people from the region. Here we use geologic, geodetic and seismic data to show that the earthquake swarm resulted from magmatic dyke intrusion. We document a surface fault rupture that is 8 km long with 91 cm of offset. Surface deformation is best modelled by the shallow intrusion of a north-west trending dyke that is about 10 km long. Seismic waves generated during the earthquakes exhibit overlapping very low- and high-frequency components. We interpret the low frequencies to represent intrusion of magma and the high frequencies to represent fracturing of the crystalline basement rocks. Rather than extension being accommodated entirely by the central Red Sea rift axis, we suggest that the broad deformation observed in Harrat Lunayyir indicates that rift margins can remain as active sites of extension throughout rifting. Our analyses allowed us to forecast the likelihood of a future eruption or large earthquake in the region and informed the decisions made by the Saudi Arabian government to return the evacuees.

  20. Monazite in Mafic Dykes from the Bastar Craton, India: Implications for LREE Depletion in Martian Basalts

    NASA Astrophysics Data System (ADS)

    Herd, C. D.; French, J. E.; Chacko, T.; Heaman, L. M.; Borg, L. E.

    2004-05-01

    multiple generations of mafic dyke swarms, and the emplacement age of one major swarm of tholeiite dykes has now been well established at ~1.9 Ga (French et al. 2004). In searching for minerals suitable for chemical and isotopic dating, a number of late-crystallizing accessory phases were found in these dykes including zircon, baddeleyite, zirconolite, allanite, and monazite. We interpret the monazite to be a primary magmatic phase on the basis of its euhedral morphology, and its occurrence as an inclusion in undoubtedly magmatic clinopyroxene. Furthermore, its Th-U-Pb chemical age is within error of emplacement ages determined for this dyke swarm, indicating that the monazite is not xenocrystic in origin. LREE-oxide concentrations in the monazite are up to 65 wt%, corresponding to ~105 to 106X CI for La-Nd and ~104X CI for Sm-Gd. Nd is fractionated from Sm by a factor of 2; La/Sm~11 and La/Gd~55. As these enrichments are crystal-chemical in nature (cf. whole-rock REE ~100X CI; La/Sm~2; Srivastava and Singh 2003), the monazite from the Bastar dykes represents a phase capable of fractionating LREE from M-HREE in mafic systems. Recognizing that studies of the stability of monazite in mafic systems at mantle pressures are required to test this hypothesis, we speculate that accessory monazite represents a possible candidate for the fractionation of LREE from M-HREE in the martian basalts.

  1. Geochronological and geochemical constraints on the petrogenesis and tectonic significance of Paleozoic dolerite dykes in the southern margin of Alxa Block, North China Craton

    NASA Astrophysics Data System (ADS)

    Duan, Jun; Li, Chusi; Qian, Zhuangzhi; Jiao, Jiangang

    2015-11-01

    Dolerite dykes are common in the southern margin of Alxa Block which is the westernmost part of North China Craton. The ages and petrogenesis of the dolerite dykes, which are important for a better understanding of tectonic-magmatic evolution in the region, are uncertain. This paper reports the results of an integrated geochronological and geochemical study of the dolerite dykes in the Jinchuan area. Previously, these dolerite dykes were considered to be coeval with the ∼831 Ma Jinchuan ultramafic intrusion by some researchers, despite a cross-cutting relationship for the dykes. Our new zircon U-Pb dating indicates that the dolerite dykes were emplaced at ∼424 Ma, >400 Ma younger than the Jinchuan intrusion. The Jinchuan dolerite dykes contain 5-9 wt.% MgO and 47-51 wt.% SiO2, and are characterized by light REE (rare earth elements) enrichments relative to heavy REE, pronounced negative Nb anomaly, elevated initial 87Sr/86Sr from 0.7056 to 0.7068, negative εNd from -2 to -5, and zircon εHf from -2 to -20. The trace element and isotope data are consistent with an asthenosphere-derived parental magma that experienced 10-25% crustal contamination prior to final emplacement. Since the Jinchuan dolerite dykes are 20-40 Ma younger than the subduction-related basaltic volcanic rocks, blueschists and eclogites in the nearby North Qilian orogenic belt to the south, we propose that the Jinchuan dolerite dykes are the products of basaltic magmatism induced by delamination of previously subducted oceanic lithosphere and the associated asthenosphere upwelling in a post-subduction setting. The occurrence of ∼424 Ma post-subduction dolerite dykes in the Jinchuan area and the ∼450 Ma arc basalts to the south indicate that the southwestern margin of North China Craton was an active plate margin in Early Paleozoic.

  2. Findings of the wetland survey of the David Witherspoon, Inc., 1630 Site, South Knoxville, Knox County, Tennessee

    SciTech Connect

    Rosensteel, B.A.

    1997-03-01

    In accordance with Department of Energy (DOE) Regulations surveys for wetland presence or absence were conducted in September 1996 on the DWI-1630 site (Witherspoon Landfill) located in South Knoxville, Knox County, Tennessee. The DWI-1630 site includes a closed, capped landfill area, areas of past disturbance adjacent to the capped area, and patches of hardwood forest. Wetlands were identified on the landfill cap and in a small bottomland that was formerly used for a retention pond in the southwest corner of the DWI-1630 site. The wetlands identified on the cap are man-induced, atypical situation wetlands. These areas have hydrophytic vegetation and wetland hydrology, but the soils do not have hydric characteristics. Wetland development appears to be due to a combination of the grading or subsidence of the clay landfill cap, the low permeability of the clay fill soil, and the absence of surface drainage outlets from the depressions. These atypical situation wetland areas may not be considered by the US Army Corps of Engineers or the State of Tennessee to be jurisdictional wetlands. The wetland in the former retention pond area has hydrophytic vegetation, wetland hydrology, and hydric soils and is a jurisdictional wetland.

  3. Linking Magma Dynamics in Dykes and Geophysical Observations: Study on the Effect of Geometrical Setting

    NASA Astrophysics Data System (ADS)

    Vassalli, M.; Montagna, C. P.; Giudice, S.; Papale, P.; Saccorotti, G.; Longo, A.

    2009-12-01

    Understanding and thus being able to detect underground magma movement inside dykes is of primary importance for the evaluation of the short term hazard at active volcanoes, especially those characterized by frequent eccentric eruptions such as Mount Etna (Italy), Kilauea and Mauna Loa (Hawaii), Nyamulagira and Nyiragongo (D.R.C.), Piton de la Fournaise (Reunion), as well as many others in the world. Magmatic fluid motion is often accompanied by distinctive low frequency seismic signals, the characteristics of which relate in complex ways to several features of the system including the geometry of the system in which fluid motion takes place, the viscosity of the fluid and the flow regime, and the properties of the surrounding rock system. We have performed a numerical simulation study to investigate the control exerted by dyke geometry on the magma flow dynamics and the associated ground displacement and seismic signals. Magma flow dynamics are simulated through the code GALES (Longo et al., 2006), which solves the two dimensional transient dynamics of multi-component fluids in compressible to incompressible regimes. The simulated systems represent volcanic dykes having different geometries from vertical with smooth walls to inclined with protrusions and indentations. The initial configuration is gravitationally unstable: a CO2-richer, lighter magma lies below a CO2-depleted, denser magma. Forced convection is induced in the system destabilizing the surface interface between the two magmas. The output of the fluid dynamics numerical simulations in terms of space-time stress distribution at the fluid-rock interface is propagated through the hosting rock medium in order to obtain synthetic seismic signals and displacement at the Earth surface. Wave propagation is performed by means of analytical Green function integration in an homogeneous half space, in order to underline the basic differences due exclusively to the geometric setting of the systems under

  4. Age and depositional setting of the Permian Black Dyke Formation: Implications for the paleogeography and structural evolution of western Nevada

    NASA Astrophysics Data System (ADS)

    Bleina, O.; Lapierre, H.; Schweickert, R. A.; Pêcher, A.; Monié, P.; Maluski, H.; Charvet, J.

    1999-09-01

    In western Nevada, the Black Dyke Formation includes volcanic rocks overlain conformably by volcaniclastic sediments. At the base, hornblende-phyric basalts with cognate hornblende-bearing gabbroic cumulates are interbedded with tuffs and pyroclastic breccia. Amphiboles give 40Ar/ 39Ar ages of 276 Ma. Clinopyroxene-phyric pillow basalts and plagioclase-phyric andesitic lava flows are present higher in the section. Facies changes between exposures reflect development near volcanic centers. According to our investigations, the Black Dyke Formation is involved in east-west-trending folds overturned toward the south, and overlain unconformably by the Mesozoic Dunlap Formation, which unconformably overlies the Mississippian-Permian Mina Formation. Interpreted until now as tectonic slices within the Luning allochthon, we suggest that the Black Dyke Formation is part of the Sonoma allochthon associated with the Mina Formation. The Sonoma records closure of the Havallah basin (Golconda allochthon), and collision of an arctrench system with the North American margin. The Black Dyke Formation exhibits similarities with the Permian arc sequence of the northern Sierra Nevada. Both sequences are characterized by amphibole-bearing breccias, clinopyroxene-phyric pillow-basalts, plagioclase-phyric andesites and overlying volcaniclastic sediments. These sequences developed in the same geodynamic environment (an islandarc).

  5. van der Waals torque

    NASA Astrophysics Data System (ADS)

    Esquivel-Sirvent, Raul; Schatz, George

    2014-03-01

    The theory of generalized van der Waals forces by Lifshtz when applied to optically anisotropic media predicts the existence of a torque. In this work we present a theoretical calculation of the van der Waals torque for two systems. First we consider two isotropic parallel plates where the anisotropy is induced using an external magnetic field. The anisotropy will in turn induce a torque. As a case study we consider III-IV semiconductors such as InSb that can support magneto plasmons. The calculations of the torque are done in the Voigt configuration, that occurs when the magnetic field is parallel to the surface of the slabs. The change in the dielectric function as the magnetic field increases has the effect of decreasing the van der Waals force and increasing the torque. Thus, the external magnetic field is used to tune both the force and torque. The second example we present is the use of the torque in the non retarded regime to align arrays of nano particle slabs. The torque is calculated within Barash and Ginzburg formalism in the nonretarded limit, and is quantified by the introduction of a Hamaker torque constant. Calculations are conducted between anisotropic slabs of materials including BaTiO3 and arrays of Ag nano particles. Depending on the shape and arrangement of the Ag nano particles the effective dielectric function of the array can be tuned as to make it more or less anisotropic. We show how this torque can be used in self assembly of arrays of nano particles. ref. R. Esquivel-Sirvent, G. C. Schatz, Phys. Chem C, 117, 5492 (2013). partial support from DGAPA-UNAM.

  6. Surface deformation and stress interactions during the 2007-2010 sequence of earthquake, dyke intrusion and eruption in northern Tanzania

    NASA Astrophysics Data System (ADS)

    Biggs, Juliet; Chivers, Michael; Hutchinson, Michael C.

    2013-10-01

    Magma movement and fault slip alter the magnitude and orientation of the stress in the surrounding crust. Observations of a sequence of events clustered in space and time provide information about the triggering mechanism and stress interactions between magma intrusion, earthquakes and eruptions. We investigate the syn- and post-intrusion stress changes associated with the 2007 Gelei dyke intrusion episode and subsequent eruption of nearby Oldonyo Lengai. Previous studies produced a kinematic model of the 2007 June-August sequence involving ˜1 m slip on a normal fault followed by the intrusion of the 7-10-km long Gelei dyke, collapse of a shallow graben and the deflation of the Gelei magma chamber. Immediately following this, the volcano Oldoinyo Lengai (<10 km away) experienced a new phase of explosive activity lasting for several months. Here, we present new geodetic observations covering Gelei and Oldoinyo Lengai in 2008 September-2010. We show continued slip on graben-bounding faults above the Gelei dyke. The eruption of Oldoinyo Lengai was accompanied by the intrusion of a 4 km-long E-W-trending dyke followed by deflation of a shallow source directly below the summit of the volcano. Next, we use stress calculations to investigate a number of hypotheses linking these events. (1) Before the onset of surface deformation, a dyke sufficiently deep and narrow to be geodetically undetectable could still have produced sufficient stress changes to trigger slip on the normal fault (i.e. the sequence could have been magmatically driven). (2) Stresses at the dyke tip would have been sufficient to overcome the effect of continued slip on the normal fault, allowing the dyke to propagate upwards into a region of clamping. (3) The Gelei sequence would have produced a significant stress change on the chamber beneath Oldoinyo Lengai. These static stress calculations allow us to discuss the roles played by dynamic stress, deeper magmatic changes and background stresses

  7. Defending commercial surrogate motherhood against Van Niekerk and Van Zyl.

    PubMed Central

    McLachlan, H V

    1997-01-01

    The arguments of Van Niekerk and Van Zyl that, on the grounds that it involves an inappropriate commodification and alienation of women's labour, commercial surrogate motherhood (CSM) is morally suspect are discussed and considered to be defective. In addition, doubt is cast on the notion that CSM should be illegal. PMID:9451602

  8. Composition of the Tarim mantle plume: Constraints from clinopyroxene antecrysts in the early Permian Xiaohaizi dykes, NW China

    NASA Astrophysics Data System (ADS)

    Wei, Xun; Xu, Yi-Gang; Luo, Zhen-Yu; Zhao, Jian-Xin; Feng, Yue-Xing

    2015-08-01

    Numerous alkaline basaltic dykes crosscut the Early Permian Xiaohaizi wehrlite in drill-cores and syenite intrusion in the Tarim large igneous province, NW China. One basaltic dyke contains abundant clinopyroxene macrocrysts with strong resorption textures. Such a textural disequilibrium is consistent with their contrasting chemistry between the macrocrysts (Mg# = 80-89) and the host dyke (Mg# = 39, corresponding to Mg# = 73 of clinopyroxene in equilibrium with the dyke), indicating that they are not phenocrysts. The clinopyroxene macrocrysts are characterized by low TiO2 (0.26-1.09 wt.%), Al2O3 (1.15-3.10 wt.%) and Na2O (0.16-0.37 wt.%), unlike those in mantle peridotites but resembling those in layered mafic intrusions in the same area. The clinopyroxene macrocrysts and the clinopyroxenes from the Xiaohaizi cumulate wehrlites define a coherent compositional trend and have identical trace element patterns, pointing to a comagmatic origin for these crystals. Accordingly, the macrocrysts cannot be xenocrysts foreign to the magmatic system. Rather they are antecrysts that crystallized from progenitor magmas and have been reincorporated into the host dyke before intrusion. The 87Sr/86Sri (0.7035-0.7037) and εNdi (4.5-4.8) of the clinopyroxene macrocrysts with high Mg# (80-89) are apparently lower and higher than their respective ratios of the clinopyroxenes in the wehrlites (Mg# = 75-84, 87Sr/86Sri = 0.7038-0.7041, εNdi = 1.0-1.9). This difference in isotopes can be accounted for by assimilation and fractional crystallization (AFC) process operated during the formation of the Xiaohaizi intrusion. In this sense, the clinopyroxene macrocrysts record the composition of the uncontaminated Tarim plume-derived melts.

  9. Complex Dyke Emplacement at the Hyper-Inflated EPR 16°N Segment

    NASA Astrophysics Data System (ADS)

    Dyment, J.; Deschamps, A.; Gente, P.; Agranier, A.; Aquilon-Robles, A.; Benoit, M.; Hémond, Ch.; Janin, M.; Maia, M.; Rodrigues-Leon, L.; Szitkar, F.; Thibaud, R.; Tilot, V.; Parisub Scientific Party

    2010-12-01

    neovolcanic zone. To this end, we have used the magnetic data, adequately corrected for the effect of the AUV and reduced to total field anomaly. The resulting magnetic map shows a set on negative anomalies associated to some - but not all - grabens and help to discriminate between recently active and inactive grabens. Indeed, such negative anomalies have already been observed by Shah et al. (JGR, 2003) on the EPR at 17°28’S and 18°37’S and interpreted as marking the presence of hot dyke swarms, warmer than the Curie temperature, and the associated demagnetization of nearby basalt. Forward modelling by these authors suggests that such an anomaly can remain during about century. On the EPR 16°N, the presence of several anomalies suggests that, in some areas, several dyke swarms are “simultaneously” active (at the scale of a century). The intensity of these anomalies may reflect the size and/or the age of the dyke swarms, the stronger anomalies corresponding to the larger and/or the hottest (and therefore most recent) dykes.

  10. Adult Presentation of Dyke-Davidoff-Masson Syndrome: A Case Report

    PubMed Central

    Roy, Ujjawal; Panwar, Ajay; Mukherjee, Adreesh; Biswas, Debsadhan

    2016-01-01

    Dyke-Davidoff-Masson syndrome (DDMS) is a rare disease which is clinically characterized by hemiparesis, seizures, facial asymmetry, and mental retardation. The classical radiological findings are cerebral hemiatrophy, calvarial thickening, and hyperpneumatization of the frontal sinuses. This disease is a rare entity, and it mainly presents in childhood. Adult presentation of DDMS is unusual and has been rarely reported in the medical literature. Key Messages DDMS is a rare disease of childhood. However, it should be kept in mind as a diagnostic possibility in an adult who presents with a long duration of progressive hemiparesis with seizures and mental retardation. Cerebral hemiatrophy, calvarial thickening, and hyperpneumatization of the frontal sinuses are diagnostic for this illness on brain imaging. PMID:26933427

  11. Dyke-Davidoff-Masson Syndrome. An unusual cause of status epilepticus.

    PubMed

    Zawar, Ifrah; Khan, Ashfa A; Sultan, Tipu; Rathore, Ahsan W

    2015-10-01

    The Dyke-Davidoff-Masson Syndrome (DDMS) results from an insult to the growing brain in utero or early infancy, which lead to loss of neurons compromising the growth of the brain. Clinical presentation includes seizures, hemiparesis, facial asymmetry, and learning disability. Radiological findings include cerebral atrophy on one side. Here, we present a case with status epilepticus who had underlying DDMS. It is a rare syndrome and uncommon cause for status epilepticus. Infections of CNS, hypoxic ischemic encephalopathy, intracranial bleed, trauma, congenital vascular malformations are the common causes of this syndrome. Diagnosis is established after clinical history, examination, and MRI. Intractable seizures can be controlled with appropriate anticonvulsants. Subsequently, these children may require physiotherapy, speech therapy, and occupational therapy in addition to the anticonvulsant medication. Outcome is better if the seizures are controlled. PMID:26492121

  12. Dyke propagation and tensile fracturing at high temperature and pressure, insights from experimental rock mechanics.

    NASA Astrophysics Data System (ADS)

    Bakker, Richard; Benson, Philip; Vinciguerra, Sergio

    2014-05-01

    It is well known that magma ascends trough the crust by the process of dyking. To enable dyke emplacement, basement rocks typically fail in a mode 1 fracture, which acts as conduits for magma transport. An overpressure of the ascending magma will further open/widen the fracture and permit the fracture to propagate. In order to further understand the emplacement and arrest of dykes in the subsurface, analogue and numerical studies have been conducted. However, a number of assumptions regarding rock mechanical behaviour frequently has to be made as such data are very hard to directly measure at the pressure/temperature conditions of interest: high temperatures at relatively shallow depths. Such data are key to simulating the magma intrusion dynamics through the lithologies that underlie the volcanic edifice. Here we present a new laboratory setup, which allows us to investigate the tensile fracturing properties under both temperature and confining pressure, and the emplacement of molten material within the newly formed fracture. We have modified a traditional tri-axial test assembly setup to be able to use a Paterson type High Pressure, High Temperature deformation apparatus. Sample setup consists of cylindrical rock samples with a 22 mm diameter and a 8 mm bore at their centre, filled with a material chosen as such that it's in a liquid state at the experimental temperature and solid at room temperature to enable post-experiment analysis. The top and lower parts of the rock sample are fitted with plugs, sealing in the melt. The assembly is then placed between ceramic pistons to ensure there are no thermal gradients across the sample. The assembly is jacketed to ensure the confining medium (Ar) cannot enter the assembly. A piston is driven into the sample such that the inner conduit materials pressure is slowly increased. At some point a sufficient pressure difference between the inner and outer surfaces causes the sample to deform and fail in the tensile regime

  13. Strain accommodation by slow slip and dyking in a youthful continental rift, East Africa.

    PubMed

    Calais, Eric; d'Oreye, Nicolas; Albaric, Julie; Deschamps, Anne; Delvaux, Damien; Déverchère, Jacques; Ebinger, Cynthia; Ferdinand, Richard W; Kervyn, François; Macheyeki, Athanas S; Oyen, Anneleen; Perrot, Julie; Saria, Elifuraha; Smets, Benoît; Stamps, D Sarah; Wauthier, Christelle

    2008-12-11

    Continental rifts begin and develop through repeated episodes of faulting and magmatism, but strain partitioning between faulting and magmatism during discrete rifting episodes remains poorly documented. In highly evolved rifts, tensile stresses from far-field plate motions accumulate over decades before being released during relatively short time intervals by faulting and magmatic intrusions. These rifting crises are rarely observed in thick lithosphere during the initial stages of rifting. Here we show that most of the strain during the July-August 2007 seismic crisis in the weakly extended Natron rift, Tanzania, was released aseismically. Deformation was achieved by slow slip on a normal fault that promoted subsequent dyke intrusion by stress unclamping. This event provides compelling evidence for strain accommodation by magma intrusion, in addition to slip along normal faults, during the initial stages of continental rifting and before significant crustal thinning. PMID:19079058

  14. Dyke-davidoff-masson syndrome: cases of two brothers and literature review.

    PubMed

    Park, Kyung-Il; Chung, Jae-Myun; Kim, Ji-Young

    2014-06-01

    Dyke-Davidoff-Masson syndrome (DDMS) has cerebral hemiatrophy and compensatory ipsilateral skull thickening, and is manifested by recurrent seizures and hemiparesis. We present one case with typical DDMS, who had a brother suffering from epilepsy with mild imaging abnormality relevant to DDMS and similar seizure semiology. A 26-year-old man had a history of developmental delay, mental retardation, hemiparesis and recurrent seizures. His brother, 23-year-old man had also experienced recurrent seizures, but he had no neurological deficits. Older brother experienced focal motor seizures with/without secondary generalization. Sometimes, he noted an auditory aura. MRI demonstrated the hemispheric atrophy with the adjacent bony hypertrophy. The seizures of younger brother were mainly of the auditory type and the MRI showed mild hemispheric atrophy with hippocampal sclerosis without any bony change. Our sibling cases might have a familial predisposition and support the idea that clinical courses and radiological findings of DDMS are varied even within one family. PMID:24977128

  15. Ages of Zircons from Basalt of Erdaogou Formation and Diabase Dyke Swarms in Northern Liaoning

    NASA Astrophysics Data System (ADS)

    SONG, Biao; QIAO, Xiufu

    The drainage area of Fanhe River around the Tieling City in the northern part of Liaodong Peninsula, is located in the north of the Tancheng-Lujiang fault zone, and belongs to the northeastern end of North China Block in the Sino-Korean plate. In this area, there is huge-thick basalt (Erdaogou Formation) and diabase dyke swarms, which are thought to be Mesoproterozoic basic magmatism. By means of zircon dating with sensitive high-resolution ion microprobe (SHRIMP), the eruption time of the Erdaogou Formation basalt is considered to be 36.4 ± 1.8 Ma, the Eocene Epoch. The emplacement time of the diabase swarms is considered to be 93.5 ± 1.4 Ma, the Late Cretaceous. The basic dyke swarms and basalts in the northern Liaoning were determined as Mesozoic and Cenozoic, respectively. This shows that the northern boundary that divides North China Block and Jiao-Liao-Korean Block within Sino-Korean Plate (i.e. the northern part of the Tancheng-Lujiang fault zone), was in a stretch-tensile tectonic environment in EW direction in Late Cretaceous. In addition, this tectonic environment resulted in the intrusion of the diabase swarms. In Paleogene Period, the stretching direction was changed to near SN, and the formation of the stretching tectonics led to the eruption of the huge-thick Erdaogou Formation basalt. The new SHRIMP zircon U-Pb ages in this article does not support the traditional opinion that the Erdaogou Formation basalt was formed in Mesoproterozoic.

  16. Single Silicate Crystal Paleointensity Analyses of the ca. 2.575 Ga Great Dyke of Zimbabwe

    NASA Astrophysics Data System (ADS)

    O'Brien, T.; Tarduno, J. A.; Hofmann, A.

    2014-12-01

    Recent considerations of core thermal conductivity suggest a relatively young (less than 1 billion-year-old) age for the inner core, excluding compositional convection associated with inner core growth as a driving mechanism for an Archean geodynamo. These reconsiderations provide further motivation for studying the nature of the field when core convection was predominantly related to core mantle boundary heat flow. Here we examine the ca. 2.575 Ga Great Dyke of Zimbabwe. We rely on deep drill core samples, eliminating the otherwise pervasive effects of lightning seen in surface samples. We apply single silicate crystal paleointensity (SCP) techniques (Tarduno et al., Rev. Geophys., 2006) on feldspars separated from orthopyroxene gabbros (norites). Scanning electron microscope (SEM) analyses indicate the presence of rare sub-micron equant to slightly elongate magnetic inclusions in the feldspars. The magnetite/titanomagnetite needles commonly observed in feldspars of slowly cooled igneous rocks are rarely observed in crystals from our Great Dyke gabbro samples. Selection criteria of crystals for analyses required feldspar crystals to be free of visible multi-domain inclusions. Natural remanent magnetic intensities of ca. 1 mm-sized feldspar crystal are relatively weak (approximately 1-2 x 10-8 emu), but well within the measurement range of the University of Rochester small bore ultra-high moment resolution 2G DC SQUID magnetometer. Preliminary total thermal demagnetization experiments suggest paleofield values within 50% of those of the present-day, similar to other results that imply a relatively strong magnetic field during the late Archean. Results from Thellier analyses will be used to test this interpretation.

  17. 1.99 Ga mafic dykes of the Lewisian Gneiss Complex of Scotland: An upper age limit for the Palaeoproterozoic Loch Maree Group

    NASA Astrophysics Data System (ADS)

    Baker, Thomas; Prave, Tony; Spencer, Christopher

    2015-04-01

    Mafic dyke swarms are often used as geochronological markers, as they are widespread and emplaced over short timespans. The ca. 2.4 Ga Scourie dyke swarm is one such example that has played a key role in understanding the complex tectonic and metamorphic history of the Lewisian Gneiss Complex of Scotland (LGC), part of the North Atlantic Craton (NAC). The LGC consists of Archean and Palaeoproterozoic terranes that experienced polyphase deformation prior to their assembly at ca. 1.8 Ga. Zircons separated from a doleritic dyke from the Gairloch terrane have yielded a concordant U-Th-Pb age (1,989 +4.3 / -0.99 Ma) using the ID-TIMS method. The doleritic dyke is emplaced in Lewisian gneiss that experienced both granulite and amphibolite-facies metamorphism. Partial recrystallisation and amphibolitisation of the dyke demonstrate that it pre-dates the most recent (Laxfordian) amphibolite-facies metamorphic event. The age obtained from the dyke overlaps the U-Pb age of a previously dated olivine gabbro dyke from the Assynt terrane (1,992 Ma). These combined ages provide strong corroborating evidence for a ca. 2.0 Ga mafic dyke swarm event, distinct from the older ca. 2.4 Ga Scourie dyke event known from elsewhere in the LGC. The existence of a ca. 2.0 Ga mafic dyke swarm provides an upper age limit for the Loch Maree Group (LMG), a Palaeoproterozoic succession of metasediment and metavolcanic rocks that overlie the LGC and which are not cross-cut by the Scourie dykes. This study proposes that a period of crustal extension took place in the region at ca. 2.0 Ga. Later, subduction may have resulted in the accretion of the LMG and the adjacent Ard Gneiss, which has previously been regarded as a magmatic arc. The ca. 1.9 Ga age of the earliest stage of the Laxfordian metamorphic event, which affected the LMG, could therefore mark the onset of collision. This sequence of events can be correlated with other coeval areas of the NAC, including the Nagssugtoqidian mobile belt of

  18. The homeodomain transcription factor Prep1 (pKnox1) is required for hematopoietic stem and progenitor cell activity.

    PubMed

    Di Rosa, Patrizia; Villaescusa, J Carlos; Longobardi, Elena; Iotti, Giorgio; Ferretti, Elisabetta; Diaz, Victor M; Miccio, Annarita; Ferrari, Giuliana; Blasi, Francesco

    2007-11-15

    Most of the hypomorphic Prep1(i/i) embryos (expressing 3-10% of the Prep1 protein), die between E17.5 and P0, with profound anemia, eye malformations and angiogenic anomalies [Ferretti, E., Villaescusa, J.C., Di Rosa, P., Fernandez-Diaz, L.-C., Longobardi, E., Mazzieri, R., Miccio, A., Micali, N., Selleri, L., Ferrari G., Blasi, F. (2006). Hypomorphic mutation of the TALE gene Prep1 (pKnox1) causes a major reduction of Pbx and Meis proteins and a pleiotropic embryonic phenotype. Mol. Cell. Biol. 26, 5650-5662]. We now report on the hematopoietic phenotype of these embryos. Prep1(i/i) fetal livers (FL) are hypoplastic, produce less common myeloid progenitors colonies (CFU-GEMM) in cytokine-supplemented methylcellulose and have an increased number of B-cells precursors that differentiate poorly. Prep1(i/i) FL is able to protect lethally irradiated mice only at high cell doses but the few protected mice show major anomalies in all hematopoietic lineages in both bone marrow (BM) and peripheral organs. Prep1(i/i) FL cells compete inefficiently with wild type bone marrow in competitive repopulation experiments, suggesting that the major defect lies in long-term repopulating hematopoietic stem cells (LTR-HSC). Indeed, wt embryonic expression of Prep1 in the aorta-gonad-mesonephros (AGM) region, fetal liver (FL), cKit(+)Sca1(+)Lin(-)AA4.1(+) (KSLA) cells and B-lymphocytes precursors agrees with the observed phenotype. We therefore conclude that Prep1 is required for a correct and complete hematopoiesis. PMID:17904118

  19. MODELING POTENTIAL IMPACTS OF SO2 CO-INJECTED WITH CO2 ON THE KNOX GROUP, WESTERN KENTUCKY

    SciTech Connect

    Zhu, Junfeng; Harris, David; Leetaru, Hannes

    2014-09-30

    Understanding potential long-term impacts of CO2 impurities, such as sulfur and nitrogen compounds, on deep carbon storage reservoirs is of considerable interest because co-injection of the impurities with CO2 can bring significant economic and environmental benefits. The Cambrian–Ordovician Knox Group, a thick sequence of dolostone (Beekmantown Dolomite) with minor dolomitic sandstone (Gunter Sandstone), in western Kentucky, USA, has been evaluated as a prospective CO2 sequestration target. In this study, TOUGHREACT was used to build 1-D radial models to simulate the potential impacts of co-injected CO2 and SO2 on minerals, pore fluids, and porosity and permeability in the Beekmantown Dolomite and the Gunter Sandstone. Co-injection of a mass ratio of 2.5 percent SO2 and 97.5 percent CO2, representative of flue gas from coal-fired plants, was simulated and the co-injection simulations were compared to models with CO2 only injections. The model results suggest that the major impacts of added SO2 for both the Beekmantown and the Gunter rocks were significant enhancement of dissolution of dolomite and precipitation of anhydrite, leading to noticeable increases in porosity and permeability. The Gunter Sandstone appeared to be more active with SO2 than the Beekmantown Dolomite. More dolomite was dissolved in the Gunter than in the Beekmantown with the same SO2 impurity. Consequently, porosity was raised more in the Gunter than in the Beekmantown. On the other hand, the impacts on aluminosilicate minerals appeared to be insignificant in both reservoirs, slightly changing the rates of precipitation/dissolution but the overall reaction paths remained the same.

  20. Strategic influence on deep groundwater flow in the Knox Group Copper Ridge dolomite on the West Chestnut Ridge site

    SciTech Connect

    Lee, R.R.; Ketelle, R.H.

    1987-10-01

    The Copper Ridge Dolomite of the Upper Cambrian Knox Group underlies a site at Oak Ridge, Tennessee, under consideration by the Department of Energy (DOE) for a belowground waste disposal facility. The Copper Ridge was studied for DOE to understand the influence of lithology on deep groundwater flow. Three facies types are distinguished which comprise laterally continuous 1 to 4-m-thick rock units interpreted to represent upward-shallowing depositional cycles having an apparently significant effect on groundwater flow at depth. Rock core observations indicate one of the recurring facies types is characterized by thin to medium-bedded, fine-grained dolostone with planar cryptalgal laminae and thin shaley partings. Distinctive fracturing in this facies type, that may have resulted from regional structural deformation, is considered to be responsible for weathering at depth and the development of stratabound pathways of preferred groundwater flow. In addition, geophysical data suggest that one occurrence of this weathered facies type coincides with an apparent geochemical interface at depth. Geophysical data also indicate the presence of several fluid invasion horizons, traceable outside the study area, which coincide with the unweathered occurrence of this fine-grained facies type. The subcropping of recurrent zones of preferred groundwater flow at the weathered/unweathered interface may define linear traces of enhanced aquifer recharge paralleling geologic strike. Vertical projection of these zones from the weathered/unweathered rock interface to the ground surface may describe areas of enhanced infiltration. Tests to determine the role of stratigraphic controls on groundwater flow are key components of future investigations on West Chestnut Ridge.

  1. Post-collisional magmatism associated with Variscan orogeny in the Danubian Domain (Romanian Southern Carpathians): the Motru Dyke Swarm

    NASA Astrophysics Data System (ADS)

    Stremtan, C. C.; Campeanu, M.; Balica, C.; Ryan, J. G.; Savov, I. P.; Balintoni, I.

    2012-12-01

    The metamorphic basement of the Danubian nappe system in the Romanian Southern Carpathians is comprised of Neoproterozoic high-grade metamorphics and granitoid intrusions, underlying low-grade Ordovician to early Carboniferous formations. This entire sequence is intruded by late Variscan age (Carboniferous to early Permian) post-collisional granitoid plutons. The Motru Dyke Swarm (MDS), a geographically-extensive system of intermediate to felsic dykes crosscuts the whole Danubian basement. Zircon U/Pb results on some MDS dikes indicate a largely inherited zircon population with an age distribution pointing to Pan-African origins and a peri-Amazonian provenance for MDS crustal sources. However, in the field the MDS dykes cross-cut late Variscan post-collisional plutons, supporting the assertion that these dykes are much younger, with Upper Paleozoic, most likely Carboniferous (Variscan) ages. This study is aimed at providing a better understanding of the petrogenesis, emplacement age, and evolution of the MDS using zircon U/Pb dating, geochemical, isotope, and petrographic data. The dykes record heterogeneous petrographic and geochemical (major and trace elements, as well as radiogenic isotope) signatures. MDS dykes are mainly basaltic-andesite, andesite, trachyandesite, and dacite in composition and petrography with porphyritic basaltic andesites being the most common. The absence of olivine and the presence of brownish amphibole, biotite- and quartz-mantled zircons, as well as mm- to cm-size enclaves of meta-sediments are the most distinctive petrologic features of the MDS. Published[1] major elements compositions define a complete differentiation series, ranging from basaltic andesites to rhyolites (50-72 wt% SiO2) with medium-K to shoshonitic calc-alkaline characteristics. The dykes are dominantly metaluminous (average ASI of 0.90). Considerable heterogeneity is preserved in their trace element compositions: ΣREE ranges from 41.18 to 378, Eu/Eu* from 0.79 to 1

  2. Ellis van Creveld syndome.

    PubMed

    Ghanekar, Jaishree; Sangrampurkar, Sujata; Hulinaykar, Raman; Ahmer, Tariq

    2009-07-01

    Ellis-van Creveld syndrome (EVC) or chondroectodermal dysplasia is a rare autosomal recessive disorder. It is a tetrad of chondrodysplasia, ectodermal dysplasia, polydactyly, and congenital heart disease. In several case reports, dysplasia involving other organs has also been identified. The exact prevalence is unknown, but the syndrome seems more common among the Amish community. Many Indian cases have also been reported. This report describes a classical case of EVC syndrome in a 22 year old woman of Indian origin born of a consanginous marriage. The patient had chondrodysplasia of tubular bones resulting in disproportionate dwarfism, postaxial polydactyly, severely dystrophic nails, partially absent teeth, pectus excavatum with narrow chest, knock knees and AV canal defect. PMID:20329417

  3. Influence of dyke geometry on the dynamics of magma flow and associated ground displacement and seismic signals

    NASA Astrophysics Data System (ADS)

    Montagna, C. P.; Longo, A.; Vassalli, M.; Papale, P.; Saccorotti, G.; O'Brien, G.; Bean, C.

    2009-04-01

    Detecting underground magma movement in dykes is of primary importance for the evaluation of the short term hazard at active volcanoes, especially those characterized by frequent eccentric eruptions like Mount Etna (Sicily), Kilauea and Mauna Loa (Hawaii), Nyamulagira and Nyiragongo (D.R.C.), Piton de la Fournaise (Reunion), and many others in the world. Fluid motion is often accompanied by distinctive low frequency seismic signals, the characteristics of which relate in complex ways to several characteristics of the volcanic system including the geometry of the crack through which fluid motion takes place, the viscosity and the flow regime of the fluid, the elastic properties and heterogeneities of the rock system, and so on. We have undertaken a numerical simulation study to investigate the control exerted by dyke geometry on the magma flow dynamics and associated ground displacement and seismic signals. Magma flow dynamics are simulated through the code GALES (Longo et al., 2006), which solves the 2D transient dynamics of multi-component fluids in compressible to incompressible regimes. The simulated system is represented by volcanic dykes having different geometries from vertical with smooth walls to inclined with protrusions and indentations. Fluid flow is allowed to occur by considering an initial gravitationally unstable condition with CO2-rich, lighter magma placed below a CO2-poor, denser magma. Both natural convection and forced convection (with prescribed overpressure applied at dyke base) are taken into account. The output of GALES in terms of time-space stress distribution at the fluid-rock interface is employed as the boundary condition for the simulation of elastic wave propagation in the surrounding rock system. This is done by employing a numerical code based on a discrete elastic lattice method (O'Brien and Bean, 2004) which accounts for complex topography and rock heterogeneities. The numerical results illustrate the complex time

  4. A new 200 Ma paleomagnetic pole for Africa, and paleo-secular variation scatter from Central Atlantic Magmatic Province (CAMP) intrusives in Morocco (Ighrem and Foum Zguid dykes)

    NASA Astrophysics Data System (ADS)

    Palencia-Ortas, A.; Ruiz-Martínez, V. C.; Villalaín, J. J.; Osete, M. L.; Vegas, R.; Touil, A.; Hafid, A.; McIntosh, G.; van Hinsbergen, D. J. J.; Torsvik, T. H.

    2011-06-01

    Available apparent polar wander (APW) paths for the 200 Ma configuration of Pangea, just prior to the opening of the Central Atlantic Ocean, differ as much as 10o in arc length. Here, we add new data from northwest Africa for this time, obtained from the northeast-trending Foum-Zguid and Ighrem dykes (ca. 200 Ma). These dykes form part of the northern domain of the Central Atlantic Magmatic Province (CAMP), and crosscut the Anti-Atlas Ranges in Morocco, and compositionally correspond to quartz-normative tholeiites intruded in continental lithosphere shortly before the opening of the Central Atlantic Ocean. The Foum-Zguid dyke has been intensively studied, whereas the Ighrem dyke has received less scientific focus. We sampled both dykes for paleomagnetic investigation along 100 km of each dyke (12 sites for Foum-Zguid and 11 for Ighrem, 188 samples included in the final analyses). Rock magnetic experiments indicate a mixture of multidomain and single-domain magnetite and/or low-Ti titanomagnetite particles as the principal remanence carriers. In both dykes, the primary nature of the characteristic remanent magnetization is supported by positive contact tests, related to Fe-metasomatism or baked overprints of the corresponding sedimentary country rocks. The directions of the characteristic magnetization exhibit exclusively normal polarity. Site-mean virtual geomagnetic poles are differently grouped in each dyke, suggesting distinct geomagnetic secular variation records. The Foum-Zguid paleomagnetic pole (N= 12, PLat= 67.9°N, PLon= 247.9°E, κ= 125, A95= 3.9°) plots close to that of Ighrem (N= 11, PLat= 78.4°N, PLon= 238.2°E, κ= 47, A95= 6.7°), confirming those mineralogical and geochemical evidences supporting that they represent dissimilar magmatic stages. Virtual geomagnetic poles dispersion from both dykes (S= 10.5°13.0°8.1°) is in line with those obtained from recent studies of a CAMP-related dyke in Iberia and results from CAMP lavas in the Argana

  5. Link between extension, dyking and subsidence as the reconstruction tool of intraplate rifting mechanism (backstripping data, modelling and geochronology)

    NASA Astrophysics Data System (ADS)

    Polyansky, Oleg P.; Reverdatto, Vladimir V.; Babichev, Alexey V.

    2014-05-01

    Correlation between subsidence and extension-related magmatism is key in determining mechanism of intracratonic sedimentary basins formation. The total volume of basic sheet intrusions and volcanics within sedimentary rock mass characterizes indirectly the degree of depletion and thinning of the rifted mantle lithosphere. At present the documented features of real-world intracontinental basins show a wide range of parameters characterizing the duration and rate of subsidence, degree of extension/thinning of the lithosphere, age and extent of dyking. For creation of general model of continental rifting it is important to reconstruct an evolution of basins finished at the continental stage, not entered an oceanic spreading phase. One of examples of such structure is the Vilyui sedimentary basin in the eastern Siberian Platform which includes the massive emplacements (10**5 km3) of extrusive and intrusive rocks of the Vilyui large igneous province. We combine backstripping reconstructions of sedimentation and thermal regime during the subsidence with a numerical modelling based on the deformable solid mechanics. It is the first time that the evolution of sedimentation and subsidence which is nonuniform over the basin area has been analyzed for the Vilyui basin. The rift origin of the basin is proved. We estimate the spatial distribution of the parameters of crustal and mantle-lithosphere extension as well as expansion due to dike intrusions. According to the reconstructions, the type of subsidence curves for the sedimentary rocks of the basin depends on the tectonic regime of sedimentation in individual subbasins. The backstripping analysis revealed two stages of extension (sediments 4-5 km thick) and a foreland stage (sediments >2 km thick). With the two-layered lithosphere model, we concluded that the subcrustal layer underwent predominant extension (by a factor of 1.2-2.0 vs. 1.1-1.4 in the crust). In each section, dyke-related extension due to basic intrusion is

  6. Seismic constraints on a large dyking event in Western Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Ahmed, A.; Doubre, C.; Leroy, S.; Perrot, J.; Audin, L.; Rolandone, F.; Keir, D.; Al-Ganad, I.; Khanbari, K.; Mohamed, K.; Vergne, J.; Jacques, E.; Nercessian, A.

    2012-04-01

    In November 2010, a large number of events were recorded by the world seismic networks showing important activity occurring along the western part of the Aden Ridge. West of the Shulka El Sheik transform zone, events in this large seismic swarm (magnitudes above 5) occurred in a complex area, where the change of both the ridge direction and the bathymetry suggest the propagation of the ridge into a continental lithosphere and the influence of the thermal anomaly of the Afar Hot Spot. We combine several sets of data from permanent networks and temporary 3C broad stations installed after the beginning of the event along the southern and eastern coasts of Yemen and Djibouti respectively, we located more than 600 earthquakes with magnitudes ranging from 2.5 to 5.6 that occurred during the first months following the first event. The spatial distribution of the main seismicity reveals a very clear N115°-trending alignment, parallel to the mean direction of the en-echelon spreading segments that form the ridge at this longitude. Half of the events, which represent half of the total seismic energy released during the first months, are located in the central third section of the segment. Here several volcanic cones and recent lava flows observed from bathymetric and acoustic reflectivity data during the Tadjouraden cruise (Audin, 1999, Dauteuil et al., 2001) constitute the sea floor. In addition to this main activity, two small groups of events suggest the activiation of landslides into a large fan and the activity in a volcanic area 50 km due east from the main active zone. The time evolution of the seismicity shows several bursts of activity. Some of them are clearly related to sudden activities within the volcanic areas, when others exhibit horizontal migration of the events, with velocity around ~ 1 km/h. The time-space evolution of the seismicity clearly reveals the intrusion of dykes associated with magma propagation from the crustal magmatic centres into the rift

  7. Phase I archaeological survey of the proposed timber harvest area in hunting area 54 on the Fort Knox Military Reservation, Hardin County, Kentucky. Final report

    SciTech Connect

    Schenian, P.A.

    1995-07-01

    In July 1995, the Fort Knox Contract Staff Archaeologist conducted a Phase I archaeological survey of a proposed timber harvest area in Hunting Area 54 on the Fort Knox Military Reservation, Hardin County, Kentucky. The timber harvest area encompasses approximately 48 acres (19 ha) in an irregularly shaped area on the ridge tops and slopes adjoining Easy Gap Road. Only selected trees, which were marked by Forestry Section personnel prior to the archaeological survey, will be harvested for marketing, but fallen and damaged trees also will be removed. The survey resulted in the discovery of no archaeological sites. A cemetery (Cemetery Number 109 or the Stone/Hem Cemetery) is located in the project area and has considerable tree damage near it. It is recommended that the timber harvest be conducted as proposed, but that the contract staff archaeologist be on-site when the timbering is performed in the vicinity of the cemetery to assist with the protection and clean-up of the cemetery. If feasible, the cemetery should be fenced after the logging operations are completed to facilitate its future location, protection, and management.

  8. Lithostratigraphy and hydrocarbon potential of the Cambrian (pre-Knox) interval in the Conoco No. 1 Turner well, Rough Creek Graben, western Kentucky

    SciTech Connect

    Harris, D.C.

    1995-09-01

    In 1992 an important deep exploratory well was drilled in the Rough Creek Graben of western Kentucky. The Conoco No. 1 Turner well, in McLean County, reached a total depth of 14,202 feet in Precambrian granite. The objective of this well was to test potential gas reservoirs in Cambrian-age pre-Knox Group carbonates and synrift sandstones. The well encountered no commercial hydrocarbons, but provided new data on the evolution and hydrocarbon potential of the Rough Creek Graben. Encouraged by the Turner well, Conoco has drilled two additional wells in the graben. The Turner well penetrated over 4,000 feet of pre-Knox sedimentary rocks. The clastic rocks lack porosity in the Turner well (because of calcite and quartz cements), but may have reservoir potential in other parts of the basin. The oolitic dolostones contain dolomite cement, and also have no effective porosity. However, bitumen staining is present in the dolostones, indicating that oil moved through the interval. The Conoco Turner well has proven that substaintial thickness of synrift clastics and post-rift dolostones occur in the Rough Creek Graben, and that facies distribution is strongly tectonically controlled. Bitumen staining indicates that hydrocarbons were migrating in the basin, but prediction of effective porosity remains a problem in the search for Cambrian reservoirs in the Rough Creek Graben.

  9. Dynamic properties of Indiana, Fort Knox and Utah test range limestones and Danby Marble over the stress range 1 to 20 GPa

    SciTech Connect

    Furnish, M.D.

    1994-12-01

    The responses of the following carbonate materials to shock loading and release have been measured: Indiana limestone (18% porosity; saturated and dry), Jeffersonville/Louisville Limestones (Fort Knox limestone) (variable dolomitization, low porosity), Danby Marble (essentially pure calcite; low porosity), and a limestone from the Utah Test and Training Range (low porosity, with 22% silica). Various experimental configurations were used, some optimized to yield detailed waveform information, others to yield a clean combination of Hugoniot states and release paths. All made use of velocity interferometry as a primary diagnostic. The stress range of 0 - 20 GPa was probed (in most cases, emphasizing the stress range 0 -10 GPa). The primary physical processes observed in this stress regime were material strength, porosity, and polymorphic phase transitions between the CaCO{sub 3} phases I, II, III and VI. Hydration was also a significant reaction under certain conditions. The Indiana Limestone studies in particular represent a significant addition to the low-pressure database for porous limestone. Temperature dependence and the effect of freezing were assessed for the Fort Knox limestone. Experimental parameters and detailed results are provided for the 42 impact tests in this series.

  10. Gridino melange zone of the Belomorian eclogite province: Succession of tectonic events and structural position of mafic dyke swarms

    NASA Astrophysics Data System (ADS)

    Babarina, I. I.; Sibelev, O. S.; Stepanova, A. V.

    2014-07-01

    Based on relationships between Paleoproterozoic mafic dykes, lithotectonic complexes, and tectonic structures of the Gridino Zone in the Belomorian eclogite province of the Fennoscandian Shield, deformations have been divided into groups differing in age and the succession of tectonic events has been reconstructed. The formation of Neoarchean eclogite-bearing melange was related to disintegration of large eclogite sheets in the course of near-horizontal ductile flow accompanied by syntectonic granitoid magmatism, multiple migmatization, and granulite-to amphibolite-facies metamorphism. The exotic blocks, including eclogites, were incorporated into TTG gneisses as sheets and lenses up to a few hundreds of meters in thickness and oriented conformably with gneissic banding. As a result of ductile flow, the lithotectonic complexes were transported at the level of discrete brittle-ductile deformations expressed as strike-slip faults and associated folds. Under conditions of a relatively rigid medium, individual structural elements underwent rotation approximately through 90° in plan view. Under the extension regime in the Early Paleoproterozoic, several swarms of mafic dykes were injected into the already cold framework rocks, as is evident from dyke morphology. The dykes crosscut all predated structures, included turned blocks, and are therefore important reference points for subdivision of Neoarchean and Paleoproterozoic processes. The Svecofennian postdyke tectonic activity was accompanied by local shearing and boudinage of metabasic rocks, development of quartz and pegmatite veins along tension cracks, disharmonic folding, and discrete retrograde metamorphism up to amphibolite-facies conditions. The postdyke deformations did not exert a substantial effect on the previously formed regional structure.

  11. Stirling Powered Van Progam overview

    NASA Technical Reports Server (NTRS)

    Shaltens, R. K.

    1986-01-01

    The Stirling Powered Van Program (SPVP) is a multiyear, multiphase program to evaluate the automotive Stirling engine (ASE) in Air Force vans under realistic conditions. The objective of the SPVP is to transfer to manufacturer and end user(s) (i.e., on the path to commercialization) the second-generation Mod 2 ASE upon completion of the Automotive Stirling Engine Program in 1987. In order to meet this objective, the SPVP must establish Stirling performance, integrity, reliability, durability and maintainability. The ASE program background leading to the van program is reviewed and plans for evaluating the kinematic Stirling engine in Air Force vans examined. Also discussed are the NASA technology transfers to industry that have been accomplished and those which are currently being developed.

  12. Early detection of eruptive dykes revealed by normalized difference vegetation index (NDVI) on Mt. Etna and Mt. Nyiragongo

    NASA Astrophysics Data System (ADS)

    Houlié, N.; Komorowski, J. C.; de Michele, M.; Kasereka, M.; Ciraba, H.

    2006-06-01

    Flank-fissure eruptions involve lateral injection and propagation of magma in a volcanic edifice along pre-existing fractures in the direction of the rift zones where magma intrusion and lava flow production are concentrated over time. Thus, the identification and mapping of active fractures and faults is a fundamental aspect of studies of active volcanic systems. However, gradual dyke wedge emplacement at depth in well-fractured zones on volcano flanks and in volcanic rift zones does not necessarily trigger large amplitude deformation signals susceptible to be recorded months or even years before the actual eruption. Here we show that active and potentially eruptive areas can be detected up to 2 yrs before the arrival to the surface of the final eruptive dyke and venting of lava flows by processing satellite images applying a normalized difference vegetation index (NDVI) algorithm. A posteriori analysis of satellite images indeed reveals that the surficial effects of dyke wedge injection and ascent on plant growth were apparent for Mt. Etna from 2000 to 2002 and for Mt. Nyiragongo in 2001, thus months to years before they erupted.

  13. SLAM in a van

    NASA Astrophysics Data System (ADS)

    Binns, Lewis A.; Valachis, Dimitris; Anderson, Sean; Gough, David W.; Nicholson, David; Greenway, Phil

    2002-07-01

    We have developed techniques for Simultaneous Localization and Map Building based on the augmented state Kalman filter, and demonstrated this in real time using laboratory robots. Here we report the results of experiments conducted out doors in an unstructured, unknown, representative environment, using a van equipped with a laser range finder for sensing the external environment, and GPS to provide an estimate of ground truth. The goal is simultaneously to build a map of an unknown environment and to use that map to navigate a vehicle that otherwise would have no way of knowing its location. In this paper we describe the system architecture, the nature of the experimental set up, and the results obtained. These are compared with the estimated ground truth. We show that SLAM is both feasible and useful in real environments. In particular, we explore its repeatability and accuracy, and discuss some practical implementation issues. Finally, we look at the way forward for a real implementation on ground and air vehicles operating in very demanding, harsh environments.

  14. Sediment dynamics over multiple time scales in Dyke Marsh Preserve (Potomac River, VA)

    NASA Astrophysics Data System (ADS)

    Palinkas, C. M.; Walters, D.

    2010-12-01

    Tidal freshwater marshes are critical components of fluvial and estuarine ecosystems, yet sediment dynamics within them have not received as much attention as their saltwater counterparts. This study examines sedimentation in Dyke Marsh Preserve, located on the Potomac River (VA), focusing on understanding the spatial variability present over multiple time scales. Bimonthly sediment data were collected using ceramic tiles, and seasonal- and decadal-scale sedimentation was determined via 7Be (half-life 53.3 days) and 210Pb (half-life 22.3 years), respectively. Results were also compared to SET data collected by the National Park Service since 2006. Preliminary data indicate that sites at lower elevations have higher sedimentation rates, likely related to their close proximity to the sediment source. Mass accumulation rates generally decreased with increasing time scale, such that the seasonal rates were greater than the SET-derived accretion rates, which were in turn greater than the decadal-scale rates. However, the bimonthly rates were the lowest observed, probably because the sampling period (May-October 2010) did not include the main depositional period of the year, which would be integrated by the other techniques.

  15. Evidence for dyke intrusion earthquake mechanisms near long valley caldera, California

    USGS Publications Warehouse

    Julian, B.R.

    1983-01-01

    A re-analysis of the magnitude 6 earthquakes that occurred near Long Valley caldera in eastern California on 25 and 27 May 1980, suggests that at least two of them, including the largest, were probably caused by fluid injection along nearly vertical surfaces and not by slip on faults. Several investigators 1,2 have reported difficulty in explaining both the long-period surface-wave amplitudes and phases and the locally recorded short-period body-wave first motions from these events, using conventional double-couple (shear fault) source models. They attributed this difficulty to: (1) complex sources, not representable by single-fault models; (2) artefacts of the analysis methods used; or (3) effects of wave propagation through hypothetical structures beneath the caldera. We show here that the data agree well with the predictions for a compensated linear-vector dipole (CLVD) equivalent-force system3 with its principal extensional axis horizontal and trending N 55-65?? E. Such a mechanism is what would be expected for fluid injection into dykes striking N 25-35?? W, which is the approximate strike of numerous normal faults in the area. ?? 1983 Nature Publishing Group.

  16. Late Variscan postcollisional extensional events in the Danubian domain (Romania): the Motru Dyke System

    NASA Astrophysics Data System (ADS)

    Campeanu, Mara; Balica, Constantin; Balintoni, Ioan; Stremtan, Cosmin

    2013-04-01

    An extensive system of dykes, known as the Motru Dyke Swarm (MDS), penetrates through the whole Danubian basement (Neoproterozoic high-grade metamorphic rocks, granitoid plutons of the same age in addition to a range of post-collisional Variscan granitoid plutons) in a presumed pre-Ordovician thermo-tectonic event [1]. Previously considered as illustrative for a sub-volcanic event occured in the early Palaeozoic (Cambrian - Ordovician), in a oceanic arc setting, based on the crosscutting field relationships with the Variscan post-collisional granitoid plutons combined with new geochemical and isotopic data, a new tectonic setting of emplacement is inferred. Even if the new zircon U/Pb ages on some components of MDS together with already published data reported by [2] does not confirm any Variscan or Late Variscan age, based on the same field relationships an upper Carboniferous age is supposed. The MDS belongs to a major complex of calc-alkaline dykes of Pan-African origin. The entire system penetrates most of the Lainici-Paius terrane components, at a relatively high crustal level, although it penetrate also Drăgan terrane components in some places. Its components consist of medium- to high-K sub-volcanic suites, composed of numerous sub-volcanic components of basic to felsic composition. These components compile a complete medium-K calc-alkaline to shshonitic differentiation series, ranging from basaltic andesites to rhyolites (46.59-68.79 wt% SiO2). Even if the trace elements trends share some similarities to those previously reported (e.g. [2]) generally they point to source heterogeneity. Some samples reveal low abundances in Nb, P and Ti, while others show relative enrichments in these elements in addition as well as in Th, Pb, Zr and Y, pointing to already enriched sources in these incompatible elements. The trace elements concentrations proportionally decrease with the increase of the SiO2 compositions. The mafic and intermediate rocks show enrichment in

  17. Ectopic expression of Malus domestica class 1 knox genes altered growth and development of Nicotiana tabacum and Prunus domestica, and induced adventitious shoot regeneration from leaf explants without exogenous cytokinin

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Transgenic tobacco (Nicotiana tabacum L) and plum (Prunus domestica L) plants were regenerated by transforming with apple class 1 KNOX genes (MdKNP1 and MdKNP2) or a corn KN1 (ZmKN1) gene. Transgenic tobacco plants were produced in vitro from transformed leaf discs in the absence of cytokinin in th...

  18. Characterization of the effect of dyke swarms on groundwater flow in a sedimentary coastal aquifer by combined geophysical and hydrogeological modelling

    NASA Astrophysics Data System (ADS)

    Burns, C.; Comte, J.; Gaffney, L.; Ofterdinger, U.; Young, M.

    2010-12-01

    In many parts of the North Atlantic region, the Permo-Triassic New Red Sandstone constitutes an important groundwater resource for drinking, agricultural and industrial water supply, thanks to relatively high transmissivity and storage properties. Such old sedimentary basins are often intruded by Paleogene volcanic dykes generally following the extensive deep fractures associated with the Mesozoic opening of the Atlantic Ocean. From local to regional scale, the effect of dyke swarms on the groundwater flow in these aquifers (i.e. as barriers, drains, or anisotropic bands) is poorly understood due to both the discrete nature of their occurrence and in many cases the existence of overlying deposits preventing their direct observation. To the Triassic Sherwood sandstone aquifer near Belfast, Northern Ireland, a combined modeling approach has been applied on a selected coastal site to evaluate the effect of dykes on groundwater flow. Geophysics was used to detect and map the dykes and natural seawater intrusion. First, information on the location, orientation and dipping of the dykes was provided by surface geomagnetic investigations and modeling. Second, electrical resistivity tomography (ERT) was applied to image both the dykes and the groundwater salinity. Inverse modeling of resistivity data is constrained using the dyke geometries from geomagnetic modeling. Thirdly, a variable-density groundwater flow model is applied, using established hydrogeological data, to simulate both the aquifer hydrodynamics and the saltwater distribution. Finally, several scenarios of permeability properties of the dykes are tested and the results compared to the seawater distribution provided by the geo-electrical models. Such a comparison allows discrimination of unrealistic scenarios, as well as both validating the groundwater numerical model and improving its calibration. Thus, it is shown that (1) at the local scale, the dykes act as low permeability zones, i.e. relative barriers

  19. Can we see the distal dyke communicate with the caldera? Examples of temporal correlation analysis using seismicity from the Bárðarbunga volcano

    NASA Astrophysics Data System (ADS)

    Jónsdóttir, Kristín; Jónasson, Kristján; Tumi Guðmundsson, Magnús; Hensch, Martin; Hooper, Andrew; Holohan, Eoghan; Sigmundsson, Freysteinn; Halldórsson, Sæmundur Ari; Vogfjörð, Kristín; Roberts, Matthew; Barsotti, Sara; Ófeigsson, Benedikt; Hjörleifsdóttir, Vala; Magnússon, Eyjólfur; Pálsson, Finnur; Parks, Michelle; Dumont, Stephanie; Einarsson, Páll; Guðmundsson, Gunnar

    2016-04-01

    The Bárðarbunga volcano is composed of a large oval caldera (7x11 km) and fissures extending tens of kilometers away from the caldera along the rift zone, which marks the divergent plate boundary across Iceland. On August 16th, 2014 an intense seismic swarm started below the Bárðarbunga caldera and in the two weeks that followed a dyke migrated some 47 km laterally in the uppermost 6-10 km of the crust along the rift. The dyke propagation terminated in lava fields just north of Vatnajökull glacier, where a major (1.5 km3) six months long eruption took place. Intense earthquake activity in the caldera started in the period August 21-24 with over 70 M5 earthquakes accompanying slow caldera collapse, as verified by various geodetic measurements. The subsidence is likely due to magma withdrawal from a reservoir at depth beneath the caldera. During a five months period, October-February, the seismic activity was separated by over 30 km in two clusters; one along the caldera rims (due to piecewise caldera subsidence) and the other at the far end of the dyke (as a result of small shear movements). Here we present statistical analysis comparing the temporal behaviour of seismicity recorded in the two clusters. By comparing the earthquake rate in the dyke in temporal bins before and after caldera subsidence earthquakes to the rate away from these bins (background rate), we show posing a statistical p-value test, that the number of dyke earthquakes was significantly higher (p <0.05) in the period 0-3 hours before a large earthquake (>M4.6) in the caldera. Increased dyke seismicity was also observed 0-3 hours following a large caldera earthquake. Elevated seismicity in the dyke before a large caldera earthquake may occur when a constriction in the dyke was reduced, followed by pressure drop in the chamber. Assuming that the large caldera earthquakes occurred when chamber pressure was lowest, the subsiding caldera piston may have caused temporary higher pressure in the

  20. Segmented Dyke Growth and Associated Seismicity at Bárðarbunga Volcanic System (Iceland) is Driven by Non-Linear Magma Pressure Diffusion

    NASA Astrophysics Data System (ADS)

    Langenbruch, C.

    2015-12-01

    In August 2014 segmented lateral dyke growth has been observed in a rifting event at Bardarbunga volcanic system, Iceland. The temporal evolution of the magma source and the physical nature of magma flow process during dyke propagation and arrest are unclear. The epidemic-type aftershock sequence model has been used to detect fluid signals in seismicity data. We use the earthquake catalog recorded during the rifting event to reconstruct the magma flow signal at the feeding source of the dyke. We find that the segmentation of dyke growth is caused by a pulsating nature of the magma flow source. We identify two main magma flow pulses, which initiate and propagate the two main segments of the dyke. During phases of dyke arrest magma flow pulses are low and cannot further propagate the dyke. We use the reconstructed magma flow signal to set up a numerical model of non-linear magma pressure diffusion. By using the magma pressure changes resulting from magma flow, we simulate the earthquake catalog caused by the reduction of the effective principal stress. We observe an excellent agreement between the spatio-temporal characteristics of the simulated earthquake catalog and recorded seismicity. Our results suggest that the process of magma pressure relaxation can be described as a non-linear diffusion process. Because the opening of the dyke creates significant new fracture volume, the permeability of the rock is strongly increasing and the diffusion process becomes highly non-linear. Our analysis is based on lessons learned from analysis of seismicity observed during hydraulic fracturing of hydrocarbon reservoirs. Despite large differences in scale, the underlying physical processes are comparable. Finally, we analyze the decay of seismic activity after start of the effusive fissure eruption near the end of the dyke. The magma flow strongly decreases and seismic activity decays according to Omori's law, which describes the decay of aftershock activity after tectonic

  1. The Nature of Feldspar Clouding and Its Paleomagnetic Significance With Reference To The 2.45 Ga Matachewan Dyke Swarm, Canada

    NASA Astrophysics Data System (ADS)

    Halls, Henry C.; Zhang, Baoxing; Garland, Mary

    Clouding in calcic plagioclase is a common occurrence in Precambrian diabase dyke swarms worldwide, particularly those of Paleoproterozoic age. The occurrence of this clouding in 2.45 Ga Matachewan dykes within uplifted blocks of the Kapuskasing Zone (KZ) in Canada, and not in dykes of the same swarm at shallower crustal levels in surrounding terranes, suggests that the clouding is produced as a re- equilibration of the felspar in response to declining temperatures but in the presence of pressures appropriate to mid - to lower- crustal levels. We have made the following observations on feldspar separates extracted from the dykes: (1) Curie Balance, and low temperature SIRM acquisition studies show Curie temperarures of 580° C and a Verwey transition at 110-120K appropriate for Ti-poor magnetite; (2) Saturation magnetization is proportional to clouding intensity as determined from image analysis techniques; (3) Hysteresis and SEM studies indicate that the particles are small, typically about 1 micron (PSD) in size; (4) A baked contact test on cloudy feldspar dykes within the KZ is negative, but positive for dykes outside the KZ; (5) Magnetite in cloudy feldspars carries a high coercivity N component of magnetization which increases with clouding intensity, whereas dykes outside the KZ mostly carry an older R remanence; (6) Since sets of R dykes become N along strike on entering the KZ, the magnetization carried by cloudy feldspars is secondary; (7) The presence of R host rocks adjacent to an N cloudy dyke and the occasional survival of lower Hc and lower Tub R components in N cloudy dykes within the KZ suggests that the N magnetization of the feldspar magnetite is a CRM; (8) SEM shows that feldspars of different clouding intensity (from image analysis) have a near constant atomic percentage of Fe, so that the degree of clouding is determined in part by the concentration of magnetite rather than by total Fe and indicates that from 30-90% of the total Fe is used in

  2. Proterozoic Diabase Dyke Swarms of Northern Ontario: Paleomagnetic Indicators of Broad-Scale Crustal Deformation of the Archean Superior Province

    NASA Astrophysics Data System (ADS)

    Halls, H. C.

    2004-05-01

    Several Proterozoic dyke swarms, all with precise U-Pb ages, (Matachewan, Senneterre, Biscotasing, Marathon and Fort Frances) occur over an area of the southern Superior Province covering more than 300,000 square kilometres. Cutting across this region is the Kapuskasing Zone, a 500 km-long fault zone along which dextral transpression at about 1.9 to 2.0 Ga has produced crustal uplift locally in excess of 20 km and lateral fault displacements of up to 70 km (Percival and West, 1994). The 2446-2473 Ma Matachewan swarm has been a subject for study throughout the last 40 years of Canadian paleomagnetism. However only in the last 20 years has the true size of the swarm been realised (Ernst and Halls, 1984; Halls et al., 1994), and the discovery made that regional variations in the direction of primary magnetization in the dykes are intimately related to the Kapuskasing Zone (KZ). The swarm is now known to span a single reversal of the Earth's magnetic field. The younger N polarity epoch, although barely recorded in the dying stages of the intrusive episode, is well preserved in dykes within uplifted crust inside the KZ. Here fine-grained magnetite, exsolved from dyke feldspars due to slow cooling of the swarm at depth, acquired a remanence of probable thermo-chemical origin prior to or during crustal uplift (Halls and Palmer, 1990; Halls et al., 1994; Halls and Zhang, 2003). The inference is that dykes intruded during the older R polarity epoch carry a near surface primary R magnetization but have been remagnetized to N at depth. Paleomagnetic data from that part of the swarm outside the KZ are therefore dominated by the older R polarity magnetization. They show that the western half of the shield has rotated counter-clockwise about 10 to 20 degrees relative to the eastern half across the KZ (Bates and Halls, 1991; Halls and Stott, 2003). This rotation is also seen in paleomagnetic data from the 2170 Ma Biscotasing swarm, which is now known to occur on both sides of the

  3. U-Pb ages and geochemistry of mafic dyke swarms from the Uauá Block, São Francisco Craton, Brazil: LIPs remnants relevant for Late Archaean break-up of a supercraton

    NASA Astrophysics Data System (ADS)

    Oliveira, E. P.; Silveira, E. M.; Söderlund, U.; Ernst, R. E.

    2013-08-01

    The São Francisco Craton (SFC) is an Archaean craton that hosts a significant number of mafic intrusions. Previous attempts to date the igneous emplacement of these rocks are limited to a few dates of poor precision. Here, two dyke swarms from the Uauá Block in the northeastern portion of the craton were dated using U-Pb on baddeleyite (ID-TIMS) and zircon (SIMS). The older dyke swarm trends mainly N-S to NW-SE (but also NE) and comprises norite dykes, whereas the younger dykes are tholeiite and trend NE-SW. The ages of 2726.2 ± 3.2 and 2623.8 ± 7.0 Ma date dykes of noritic and tholeiitic compositions, respectively. The older age matches the ages of several Archaean-Large Igneous Provinces (tholeiitic-komatiite greenstone belts and continental flood basalts) worldwide and represents part of a feeder system, but the younger age is similar to Andean style continental margin magmatism in the São Francisco and Zimbabwe cratons. The two dyke swarms are tholeiitic in composition but the noritic dykes are more enriched in both compatible and incompatible elements and have higher (La/Yb)N ratios than the tholeiite dykes. The norite dykes are interpreted as low degrees of melting from enriched refractory mantle sources, whereas the tholeiite dykes represent high degrees of partial melting of more depleted mantle sources; the two mafic dyke swarms may be related to each other by progressive extension of the continental lithosphere. It is suggested that the Uauá Block with its dyke swarms is a small piece of Archaean crust dispersed after the break-up of a major Archaean supercraton.

  4. The Deccan tholeiite lavas and dykes of Ghatkopar-Powai area, Mumbai, Panvel flexure zone: Geochemistry, stratigraphic status, and tectonic significance

    NASA Astrophysics Data System (ADS)

    Sheth, Hetu C.; Zellmer, Georg F.; Demonterova, Elena I.; Ivanov, Alexei V.; Kumar, Rohit; Patel, Rakesh Kumar

    2014-04-01

    Mumbai City, situated on the western Indian coast, is well known for exposures of late-stage Deccan pillow basalts and spilites, pyroclastic rocks, rhyolite lavas, and trachyte intrusions. These rock units, and a little-studied sequence of tholeiitic flows and dykes in the eastern part of Mumbai City, constitute the west-dipping limb of a regional tectonic structure called the Panvel flexure. Here we present field, petrographic, major and trace element and Sr-Nd isotopic data on these tholeiitic flows and dykes, best exposed in the Ghatkopar-Powai area. The flows closely resemble the Mahabaleshwar Formation of the thick Western Ghats sequence to the east, in Sr-Nd isotopic ratios and multielement patterns, but have other geochemical characteristics (e.g., incompatible trace element ratios) unlike the Mahabaleshwar or any other Formation. The flows may have originated from a nearby eruptive center, possibly offshore of Mumbai. Two dykes resemble the Ambenali Formation of the Western Ghats in all geochemical characteristics, though they may not represent feeders of the Ambenali Formation lavas. Most dykes are distinct from any of the Western Ghats stratigraphic units. Some show partial (e.g., Sr-Nd isotopic) similarities to the Mahabaleshwar Formation, and these include several dykes with unusual, concave-downward REE patterns suggesting residual amphibole and thus a lithospheric source. The flows and dykes are inferred to have undergone little or no contamination, by lower continental crust. Most dykes are almost vertical, suggesting emplacement after the formation of the Panvel flexure, and indicate considerable east-west lithospheric extension during this late but magmatically vigorous stage of Deccan volcanism.

  5. Teleseismic earthquake swarms at ultraslow spreading ridges: indicator for dyke intrusions?

    NASA Astrophysics Data System (ADS)

    Schlindwein, V.

    2012-07-01

    Earthquakes at mid-ocean ridges reflect the active magmatic and tectonic processes that form new oceanic crust. Studies of large earthquakes observed on land and smaller earthquakes observed locally or regionally by ocean bottom seismometers or autonomous underwater hydrophones have greatly contributed to our understanding of the structure and active spreading processes at the mid-ocean ridges of the Atlantic and Pacific Ocean opening with velocities in excess of 25 mm yr-1. At spreading rates below 20 mm yr-1 full rate, the appearance and the accretion processes of mid-ocean ridges undergo fundamental changes as the melt supply is drastically reduced. The active spreading processes at these so-called ultraslow spreading ridges are still poorly known, as the main representatives, the Arctic Ridge System and the Southwest Indian Ridge, are poorly accessible and neither autonomous underwater hydrophone nor ocean bottom seismometer records of local seismicity are available. In an attempt to compare on a large scale the accretion style of ultraslow spreading ridge sections, I analyse the teleseismically recorded seismicity in 11 sections of the Arctic Ridge System and the Southwest Indian Ridge spanning altogether 7200 km. Epicentres located within 30-35 km of the rift axis were extracted from the catalogue of the International Seismological Centre for a time period of 35 yr. On the basis of a single-link cluster analysis, I identified 27 swarms with eight or more events. These swarms occur almost exclusively at centres of focussed magmatism suggesting that the swarms are probably initiated by magmatism. Normal faults along several tens of kilometres surrounding the volcanic centres react in large earthquakes (M > 5) to dyke emplacement. The routine generation of large earthquakes in the cold, brittle lithosphere of ultraslow spreading ridges makes the teleseismic record a valuable means to study ultraslow accretion processes and to provide a global framework for the

  6. A preliminary assessment of asbestos awareness and control measures in brake and clutch repair services in Knoxville and Knox County, Tennessee

    SciTech Connect

    Phillips, C.C. ); Hamilton, C.B.

    1994-04-01

    The pending OSHA standard revision proposed in 1990 to lower the asbestos Permissible Exposure Limit (PEL) and to mandate effective asbestos control measures (ACM) in brake and clutch assembly work may have a profound effect on industries involved in such operations. Health protection of workers will be improved and costs of improved control methods and training will increase. Considering these facts, this preliminary study was designed to assess the level of worker and management awareness of asbestos hazards associated with brake and clutch repair and to determine what ACM had been implemented by businesses in Knoxville and Knox County, Tennessee. The study, in a metropolitan area of approximately 336,000 people, revealed eight different categories of businesses conducting brake and clutch repair work with an estimated 363 potentially exposed employees. Results of the study suggest that managers and employees of the 80 businesses studied were in need of asbestos hazard awareness training and more adequate asbestos control measures.

  7. [The 'van der Linden' retainer].

    PubMed

    van der Linden, F P

    2003-11-01

    Normally, only the anterior teeth have to be retained after an orthodontic treatment. For that purpose, a lingually bonded wire is preferred in the mandible and a removable plate in the maxilla. The design of the Van der Linden-retainer is based on theoretical considerations and secures rigid fixation of the six anterior teeth with solid anchorage in that region. A retention plate should not be used to move anterior teeth. However, with instant corrections small improvements can be realized. The fabrication and clinical use of the Van der Linden-retainer is explained and illustrated. PMID:14669487

  8. Large-scale liquid immiscibility and fractional crystallization in the 1780 Ma Taihang dyke swarm: Implications for genesis of the bimodal Xiong'er volcanic province

    NASA Astrophysics Data System (ADS)

    Peng, Peng; Wang, Xinping; Lai, Yong; Wang, Chong; Windley, Brian F.

    2015-11-01

    Immiscibility is a potential mechanism for the formation of high-Fe-Ti-P rocks; however, whether large-scale segregation and eruption of high-Si lavas can occur in nature has yet to be proven. In this study, we investigate the possibility of immiscibility between the cogenetic 1780 Ma high-Fe-Ti-P-bearing Taihang dykes and the 'bimodal' Xiong'er volcanics in North China. The compositions of silicate melt inclusions in plagioclase megacrysts of the dykes provide a new approach to obtain the primary liquid. Mineral and bulk-rock compositions reveal that large compositional variations in the dykes are the result of plagioclase- and clinopyroxene-dominated fractional crystallization and of density-driven mineral sorting, which together caused the liquids to be poor in Ca-Al but rich in Fe-Ti-P-K, and thus chemically immiscible. Conjugate interstitial granophyric and ilmenite-rich intergrowths and reactive microstructures especially olivine coronas in the dykes, and Si-/Fe-Ti-rich globules in the volcanics, provide petrographic evidence for the presence of two coeval, coexisting liquids in equilibrium separated by a miscibility gap, and thus for immiscibility and segregation/migration. The fractional crystallization and subsequent segregation were responsible for the compositional diversity of the Taihang dykes and also of the 'bimodal' Xiong'er volcanics. Accordingly, the dacite and rhyolite lavas are potentially the high-Si counterparts of the high-Ti dykes, and the basalt and andesite lavas are the erupted equivalents of the relatively low-Ti dykes. It is likely that the sustained plagioclase- and clinopyroxene-dominated fractional crystallization, and the enhanced fO2 were responsible for the immiscibility. The segregation probably took place during the ascent of the liquid in the pumping system (feeder dykes). This likely represents one natural example of crust-scale immiscibility from which many high-Ti dykes and silicic lavas (~ 1/3 volume of the Xiong

  9. The Karoo triple junction questioned : Evidence from 40Ar/39Ar Jurassic and Proterozoïc ages and geochemistry of the Okavango dyke swarm (Botswana).

    NASA Astrophysics Data System (ADS)

    Jourdan, F.; Féraud, G.; Bertrand, H.; Kampunzu, A. B.; Tshoso, G.; Le Gall, B.; Tiercelin, J. J.

    2003-04-01

    The lower Jurassic Karoo-Ferrar magmatism represents one of the most important Phanerozoic continental flood basalt (CFB) provinces. Karoo CFB is dominated by tholeiitic traps and apparently radiating giant dyke swarms covering altogether ca 3x106 km2. This study focuses on the giant N110° oriented Okavango dyke swarm (ODS) stretching over a distance of 1500 km through Botswana. This dyke swarm represents the main arm of the so-called Karoo triple junction which is generally considered as a key marker linking the Karoo magmatism to a starting mantle plume impact (Campbell and Griffiths, 1990). ODS dolerites yield twelve reliable plagioclase 40Ar/39Ar plateau (and mini-plateau) ages ranging from 178.3 +-1.1 (2 sigma) to 179.3 +-1.2 Ma (Le Gall et al, 2002 and unpublished data). The distribution of the ages along a narrow gaussian curve suggests a short period of magmatic activity centered around 178.9 Ma. In addition, small clusters of plagioclase separated from twenty-five other dykes and measured by total fusion, gave either Karoo or Proterozoïc ages. The Proterozoïc rocks range from 758.2 +-6.6 Ma and 1223.8 +-10.0 Ma (integrated ages) and, although petrographically indistinguishable in some cases, they display clear geochemical differences (e.g. TiO2<2%, Ti/Y<400) compared to the Karoo high-Ti ODS (TiO2>2%, Ti/Y>400). Geochemical data combined with available Ar/Ar dates allowed us to identify the two groups within a total set of seventy-eight dykes investigated: about 15 % of the bulk ODS dykes were emplaced during the Proterozoïc and, thus, the Jurassic Karoo dykes were emplaced along reactivated Proterozoïc structures. The validity of the Karoo triple junction-plume model, should therefore be revisited. Although available data on Proterozoïc dykes along the ODS are not precise enough to assess their exact emplacement age, they indicate that most of the Proterozoïc dykes were emplaced between 900 and 1100 Ma. This age range is the same as dating commonly

  10. Nature of mantle source contributions and the role of contamination and in situ crystallisation in the petrogenesis of Proterozoic mafic dykes and flood basalts Labrador

    NASA Astrophysics Data System (ADS)

    Cadman, A. C.; Tarney, J.; Baragar, W. R. A.

    1995-12-01

    Proterozoic tholeiitic dyke swarms share many compositional features with, and pose similar petrogenetic problems to, Phanerozoic continental flood basalts, but there are few extrusive equivalents of such swarms. The Mesoproterozoic (1.27 Ga) Harp dyke swarm in Labrador is one where possible extrusive equivalents exist in the Seal Lake group, but are slightly displaced in space and time, and can probably be related by models of progressive crustal extension. Here we try to evaluate the roles of crystal differentiation, in situ crystallisation, crustal assimilation and the relative contributions of asthenosphere- and lithosphere-derived melts in the petrogenesis of the mafic magmas. Modelling of the major and trace element variations both within individual dykes and between dykes, and within the lava sequence, does not suggest an important role for continental crust involvement. While in situ crystallisation processes could account for some of the compositional variations, the most successful models invoke mixing or contamination of asthenospheric magmas with/by veined material in the lower lithosphere / upper asthenosphere which carries the ‘continental’ characteristics. The results imply an important role for hydrous phases such as phlogopite and hornblende in the sub-lithosphere mantle. Much of the low-MgO character of mafic dykes may result from significant removal of mafic phases during in situ crystallisation within the lithosphere.

  11. Zr-Y-Nb-REE mineralization associated with microgranite and basic dykes at EL Sela shear zone, South Eastern Desert, Egypt.

    PubMed

    Shahin, Hassan Abd El-Razek Aly

    2014-01-01

    El Sela shear zone occurs in the younger granite rock of Gabal El Sela area, south Eastern Desert, Egypt near the Sudan Frontier. It comprises lines-arranged intrusions trending ENE-WSW and extend for about 1.5 km in length and reach up to 40 meters in width. These lines-arranged intrusions include multi-phase quartz veins, altered microgranite and altered basic dykes. These dykes hosting or acting as a source for uranium, rare metals (Zr, Y, Nb and Ga) and light rare earths (La, Ce, Sm and Nd) mineralizations. They show highly alteration, uranium enrichment and a strong enrichment in some rare metals and light rare earths contents (Zr = 644, Y = 133, Nb = 136, Ga =184, La = 50.19, Ce = 105.47, Sm = 24.81, Nd = 78.91 ppm and and ∑ LREEs = 259.38.). The chondrite normalised rare earth elements trends indicate strongly fractionated rare earth elements pattern with significant enriched of LREE according to HREE in both altered microgranite and altered basic dykes. Field radiometric measurements of the studied altered microgranite dyke revealed that eU reach up to 359 ppm with an average 78 ppm, while in the altered basic dyke reach up to 1625 ppm with an average 144 ppm. PMID:25332873

  12. Calc-alkaline mafic rocks of the Black Dyke Formation: Remnants of the final activity of a submerged Permian volcano

    SciTech Connect

    Blein, O.; Lapierre, H.; Pecher, A. ); Schweickert, R.A. . Dept. of Geological Science)

    1993-04-01

    The Permian Black Dyke Fm., which occurs as large tectonic slices within the Luning allochthon in the Excelsior Mountains, NV, forms an E-W trending anticline at Black Dyke Mountain. The 800-m thick stratigraphic succession consists of volcanic and pyroclastic rocks overlain conformably by volcaniclastic sediments. Along the northern limb of the anticline, the rocks consist of mafic porphyritic lavas, breccias, and graded and ungraded pyroclastic beds. The sedimentary unit consists of thick volcaniclastic turbidites overlain by conglomerates, sandstones, and mudstones. Along the southern limb of the anticline, the sequence is replaced by reworked breccia, tuffs, and sandstones. Mafic plutonic rocks occur as xenoliths in the lavas and breccias, and as coeval plugs intruding the section. Gabbros show cumulate or porphyritic textures and are composed of amph, cpx, and zoned plag. Their Ti/V (14.5--15) and Nb/Y (0.25--0.3) ratios fall in the range commonly found in calc-alkaline rocks. Diorite porphyry shows high Al[sub 2]O[sub 3], ZrO[sub 2], and REE abundances indicating that this rock is more fractionated. Basalts and andesites are plag-cpx-opx phyric. They often include glomeroporphyritic clots of cpx with amph coronas. Some rocks exhibit fluidal textures. Both volcanic and plutonic rocks show homogeneous geochemical features and similar crystallization sequences: Fe-Ti oxides---->plag---->opx + cpx----> brown zoned hbl, suggesting that they are cogenetic. Thus, the lower part of the Black Dyke Fm. likely represents the final products formed in a calc-alkaline magma chamber because pyroclastic rocks prevail over lava flows and abundant early crystal cumulates occur as plugs or as inclusions in the lavas and breccias.

  13. The Dramatic Methods of Hans van Dam.

    ERIC Educational Resources Information Center

    van de Water, Manon

    1994-01-01

    Interprets for the American reader the untranslated dramatic methods of Hans van Dam, a leading drama theorist in the Netherlands. Discusses the functions of drama as a method, closed dramatic methods, open dramatic methods, and applying van Dam's methods. (SR)

  14. Valles Marineris as a Cryokarstic Structure Formed by a Giant Dyke System: Support From New Analogue Experiments

    NASA Astrophysics Data System (ADS)

    Ozeren, M. S.; Sengor, A. M. C.; Acar, D.; Ülgen, S. C.; Onsel, I. E.

    2014-12-01

    Valles Marineris is the most significant near-linear depression on Mars. It is some 4000 km long, up to about 200 km wide and some 7 km deep. Although its margins look parallel at first sight, the entire structure has a long spindle shape with significant enlargement in its middle (Melas Chasma) caused by cuspate slope retreat mechanisms. Farther to its north is Hebes Chasma which is an entirely closed depression with a more pronounced spindle shape. Tithonium Chasma is a parallel, but much narrower depression to its northeast. All these chasmae have axes parallel with one another and such structures occur nowhere else on Mars. A scabland surface exists to the east of the Valles Marineris and the causative water mass seems to have issued from it. The great resemblance of these chasmae on mars to poljes in the karstic regions on earth have led us to assume that they owed their existence to dissolution of rock layers underlying them. We assumed that the dissolving layer consisted of water ice forming substantial layers, in fact entirely frozen seas of several km depth. We have simulated this geometry by using bentonite and flour layers (in different experiments) overlying layers of ice in which a resistant coil was used to simulate a dyke. We used different thicknesses of bentonite and flour overlying ice layers again of various thicknesses. The flour seems to simulate the Martian crust better because on Mars, g is only about 3/8ths of its value on Earth, so (for equal crustal density) the depth to which the cohesion term C remains important in the Mohr-Coulomb shear failure criterion is about 8/3 times greater. As examples we show two of those experiments in which both the rock analogue and ice layers were of 1.5 cm. thick. Perfect analogues of the Valles Marineris formed above the dyke analogue thermal source complete with the near-linear structure, overall flat spindle shape, cuspate margins, a central ridge, parallel side faults, parallel depressions resembling

  15. Van Hiele Guidelines for Geometry.

    ERIC Educational Resources Information Center

    Davey, Geoff; Holliday, Jack

    1992-01-01

    Describes five skills underpinning the understanding of geometry for primary and lower secondary mathematics students. Skill categories identified include (1) visual; (2) verbal; (3) drawing; (4) logical; and (5) application. Gives examples of skills appropriate for Van Hiele levels 1-3. (MDH)

  16. Sentinel-1 TOPS interferometry for geophysical applications: Dyke intrusion imaged during 2014 Pico do Fogo eruption

    NASA Astrophysics Data System (ADS)

    Gonzalez, Pablo J.; Marinkovic, Petar; Samsonov, Sergey; Hooper, Andrew; Larsen, Yngvar; Wright, Tim

    2015-04-01

    apply Sentinel-1 TOPS-InSAR to illuminate the deformation accompanying a recent volcanic eruption at Pico do Fogo volcano, Fogo (Cape Verde). The detected deformation is consistent with a shallow near-vertical dyke intrusion, which fed the fissure eruption. The modelling of the deformation interferograms do not seem affected largely by the variable LoS vector, in this case. The presented results prove the potential of Terrain observation by progressive scans (TOPS) interferometry for geophysical applications, in particular using ESA Sentinel-1 mission.

  17. Geochronology and geochemistry of a dyke host rock association and implications for the formation of the Bavarian Pfahl shear zone, Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Siebel, Wolfgang; Blaha, Ulrich; Chen, Fukun; Rohrmüller, Johann

    2005-02-01

    To place constraints on the formation and deformation history of the major Variscan shear zone in the Bavarian Forest, Bavarian Pfahl zone, SW Bohemian Massif, granitic dykes and their feldspar-phyric massive host rock (so-called “palite”), zircons were dated by the U Pb isotope dilution and Pb-evaporation methods. The dated samples comprise two host rocks and four dykes from a K-rich calc-alkaline complex adjoining the SW part of the Bavarian Pfahl shear zone. The palites, which appear to be the oldest magmatic rocks emplaced in the shear zone, yield ages of 334±3, 334.5±1.1 Ma (average 207Pb/206Pb-evaporation zircon ages) and 327 342 Ma (range of U/Pb zircon ages) suggesting a Lower Carboniferous age for the initiation of the Pfahl zone. Absence of inherited older cores in all investigated zircons indicates that incorporation of crustal zircon material has played virtually no role or that the melting temperature was very high. Determination of the dyke emplacement age is complicated by partial Pb-loss in most of the fractions analysed. This Pb-loss can be ascribed to higher U content of the dyke zircons compared to those from host rock. Upper discordia intercept ages of the different dykes range from 322±5 to 331±9 Ma. The dykes are pre- to synkinematic with respect to penetrative regional mylonitisation along the Pfahl zone, and the upper intercept ages provide a maximum age for this tectonic event.

  18. Late Palaeoproterozoic mafic dyking in the Ukrainian Shield of Volgo-Sarmatia caused by rotation during the assembly of supercontinent Columbia (Nuna)

    NASA Astrophysics Data System (ADS)

    Bogdanova, Svetlana V.; Gintov, Oleg B.; Kurlovich, Dzmitry M.; Lubnina, Nataliya V.; Nilsson, Mimmi K. M.; Orlyuk, Mykhailo I.; Pashkevich, Inna K.; Shumlyanskyy, Leonid V.; Starostenko, Vitaly I.

    2013-08-01

    The Ukrainian Shield comprises the exposed crust of the large Palaeoproterozoic protocraton Volgo-Sarmatia, which together with the Fennoscandian crustal segment constitutes the East European Craton ("Baltica"). Geological and geophysical data indicate that 1.80 to 1.75 Ga mafic dykes related to anorthosite-mangerite-charnockite-granite (AMCG) plutons are widespread within the Ukrainian Shield. We examined their ages, distribution patterns, orientations and compositions in three different crustal blocks (Volyn, Ingul and Azov), and found close spatial relationships with major strike-slip fault systems developed during two phases of extension. The early, 1.80-1.77 Ga, generation of mafic dykes mostly follows NW (330 ± 20°) and more rarely N-S- or E-W-trending faults corresponding to major NE-SW extension (the Submoshorino phase). These dykes contain olivine dolerites, picrites, camptonites, lamprophyres, kimberlites and other rocks belonging to tholeiitic and subalkaline jotunitic series. The compositions of these dykes differ between the host blocks, but all feature upper mantle geochemical signatures such as high contents of Ni and Cr, and positive values of εNd(1800) up to + 2.8. High degrees of REE fractionation indicate deep levels of mantle melting, which is particularly characteristic of the Ingul block as marked by the most extensive and dense mafic dyke swarms. The later, 1.76-1.75 Ga, dyke swarms occur close to the most voluminous AMCG suites of similar age and were emplaced during the second (Korsun) phase of faulting when all the older strike-slip fault zones were reactivated and partly transformed to tensional faults by E-W extension. These dyke swarms mainly trend 030 ± 20°. They are jotunitic and their isotopic signatures indicate a greater participation of crustal sources in the parent melts. The overall transtensional tectonic setting of the mafic dyking associated with the AMCG magmatism in Volgo-Sarmatia was created by convergent tectonics

  19. Age and geochemistry of mantle peridotites and diorite dykes from the Baldissero body: Insights into the Paleozoic-Mesozoic evolution of the Southern Alps

    NASA Astrophysics Data System (ADS)

    Mazzucchelli, Maurizio; Zanetti, Alberto; Rivalenti, Giorgio; Vannucci, Riccardo; Correia, Ciro Teixeira; Tassinari, Colombo Celso Gaeta

    2010-10-01

    Trace element and isotopic data obtained for mantle spinel lherzolites and diorite dykes from the Baldissero massif (Ivrea-Verbano Zone, Western Italy) provide new, valuable constraints on the petrologic and geodynamic evolution of the Southern Alps in Paleozoic to Mesozoic times. Whole rock and mineral chemistry indicates that Baldissero lherzolites can be regarded as refractory mantle residues following limited melt extraction. In particular, the Light Rare Earth Elements (LREE)-depleted and fractionated compositions of whole rock and clinopyroxene closely match modelling results for refractory residues after low degrees (~ 4-5%) of near-fractional melting of depleted mantle, possibly under garnet-facies conditions. Following this, the peridotite sequence experienced subsolidus re-equilibration at lithospheric spinel-facies conditions and intrusion of several generations of dykes. However, lherzolites far from dykes show very modest metasomatic changes, as evidenced by the crystallisation of accessory titanian pargasite and the occurrence of very slight enrichments in highly incompatible trace elements (e.g. Nb). The Re-Os data for lherzolites far from the dykes yield a 376 Ma (Upper Devonian) model age that is considered to record a partial melting event related to the Variscan orogenic cycle s.l. Dioritic dykes cutting the mantle sequence have whole rock, clinopyroxene and plagioclase characterised by high radiogenic Nd and low radiogenic Sr, which point to a depleted to slightly enriched mantle source. Whole rock and mafic phases of diorites have high Mg# values that positively correlate with the incompatible trace element concentrations. The peridotite at the dyke contact is enriched in orthopyroxene, iron and incompatible trace elements with respect to the lherzolites far from dykes. Numerical simulations indicate that the geochemical characteristics of the diorites can be explained by flow of a hydrous, silica-saturated melt accompanied by reaction with the

  20. Dykes and structures of the NE rift of Tenerife, Canary Islands: a record of stabilisation and destabilisation of ocean island rift zones

    NASA Astrophysics Data System (ADS)

    Delcamp, A.; Troll, V. R.; van Wyk de Vries, B.; Carracedo, J. C.; Petronis, M. S.; Pérez-Torrado, F. J.; Deegan, F. M.

    2012-07-01

    Many oceanic island rift zones are associated with lateral sector collapses, and several models have been proposed to explain this link. The North-East Rift Zone (NERZ) of Tenerife Island, Spain offers an opportunity to explore this relationship, as three successive collapses are located on both sides of the rift. We have carried out a systematic and detailed mapping campaign on the rift zone, including analysis of about 400 dykes. We recorded dyke morphology, thickness, composition, internal textural features and orientation to provide a catalogue of the characteristics of rift zone dykes. Dykes were intruded along the rift, but also radiate from several nodes along the rift and form en échelon sets along the walls of collapse scars. A striking characteristic of the dykes along the collapse scars is that they dip away from rift or embayment axes and are oblique to the collapse walls. This dyke pattern is consistent with the lateral spreading of the sectors long before the collapse events. The slump sides would create the necessary strike-slip movement to promote en échelon dyke patterns. The spreading flank would probably involve a basal decollement. Lateral flank spreading could have been generated by the intense intrusive activity along the rift but sectorial spreading in turn focused intrusive activity and allowed the development of deep intra-volcanic intrusive complexes. With continued magma supply, spreading caused temporary stabilisation of the rift by reducing slopes and relaxing stress. However, as magmatic intrusion persisted, a critical point was reached, beyond which further intrusion led to large-scale flank failure and sector collapse. During the early stages of growth, the rift could have been influenced by regional stress/strain fields and by pre-existing oceanic structures, but its later and mature development probably depended largely on the local volcanic and magmatic stress/strain fields that are effectively controlled by the rift zone growth

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

    NASA Astrophysics Data System (ADS)

    Randive, Kirtikumar; Hurai, Vratislav

    2015-09-01

    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.

  2. Petrographical and geochemical characteristics of the sheeted dyke-gabbro transition zone in ODP/IODP Hole 1256D

    NASA Astrophysics Data System (ADS)

    Python, M.; France, L.; Abily, B.; Abe, N.; Alt, J. C.; Godard, M. M.; Ildefonse, B.; Koepke, J. H.; Kurtz, M. D.; Oizumi, R.; Payot, B. D.

    2012-04-01

    During IODP Expedition 335, high grade granoblastic hornfels were extensively recovered as drilling cuttings at the gabbro-sheeted dyke transition zone of ODP Hole 1256D (East Pacific Rise, 6°44.163'N, 91°56.061'W). This lithology probably results from high-temperature metamorphism of previously hydrothermally altered diabases and/or basalts; the heat source likely stems from the melt lens located at the top of the magmatic chambers imaged along present-day fast-spreading ridges. This lithology, associated with gabbroic bodies, characterises the transition zone between the sheeted dyke complex and the uppermost gabbroic section, and represents the interface between magmatic and hydrothermal convecting systems in an oceanic crust formed at fast-spreading ridges. In this study, 14 samples from the junk basket (cuttings) and 2 samples from cores obtained during Expedition 335 were observed and analysed. The petrological and chemical characteristics of 5 granoblastic samples collected during Expedition 312 at the root of the sheeted dyke complex and between two gabbroic horizons were also acquired for comparison. Samples collected during IODP Expedition 335 are mainly fine grained oxide grabbronorites composed of two pyroxenes, plagioclases and oxides (ilmenite, magnetite) with more or less amphiboles, sulphides, quartz and accessory minerals. Orthopyroxene Shape (roundish or anhedral), the amount of oxide inclusions in clinopyroxene and plagioclase morphology (laths or triple-junction mosaic) indicate various recrystallisation degrees. Plagioclases show a strong zoning in the less recrystallised samples, which tend to disappear with increasing recrystallisation degree. Samples show usually low alteration (less than 10%) with moderate transformation of pyroxenes into talc or actinolite. Samples from Expedition 312 show finer grains, higher degree of alteration (up to 30%), and weaker recrystallisation. They are mainly composed of plagioclases, amphibole and oxides

  3. A New Occurrence of Alkaline Magmatism on the Kola Peninsula: An Agpaitic Dyke in the Kandalaksha Region.

    NASA Astrophysics Data System (ADS)

    Akimenko, Mariya; Kogarko, Lia; Sorokhtina, Natalia; Kononkova, Natalia; Mamontov, Vladimir

    2015-04-01

    A new occurrence of alkaline dyke magmatism was discovered in 2010 during the geological works performed by the Murmansk Geological Prospecting Expedition in the "Mokhnatye Roga" area located 55 km to the southeast of the Kovdor massif (67°15' N, 31°30' E). The "Mokhnatye Roga" area is located in the Ensk segment of the northwestern part of the Belomorian mobile belt. We performed a complete petrological and geochemical description of the sections in Holes 19 and 24, which reveal one of the largest dykes in the area. The dyke, with a length of ≈4 km and a width of ≈160 m, has an eastern orientation with steep dipping (60°-90°) to the north. The thickness of Quaternary deposits ranges from 0.8 to 4.0 m; alkaline rocks occur in the range of 4.0-93.9 m being followed by host amphibole-biotite gneiss with interbeds of plagioamphibolite (AR2 mt) along the section. Among the major minerals of the dyke are the minerals of the lamprophyllite group (20-25 vol %), aegirine-augite (10-15 vol %), enigmatite (10-15 vol %), nepheline (10-15 vol %), orthoclase (15-20 vol %), alkaline amphibole (5-10 vol %), and astrophyllite (up to 5 vol %). The minor minerals are represented by shcherbakovite, sodalite, natrolite, barite, Mn carbonate, ilmenite, rutile, sphalerite, and goethite. The texture of the rock is porphyric: the groundmass is composed of finegranular nepheline and orthoclase, which are observed as individual large euhedral crystals as well. In addition, large phenocrysts are represented by the minerals of the lamprophyllite, enigmatite, pyroxene, and alkaline amphibole groups. Based on the generally accepted classifications [1], the studied agpaitic rock may be related to nepheline syenite; according to the mineral and chemical compositions, it is close to syenite of the Niva massif [2] located 35 km to the northeast from the "Mokhnatye Roga" area. Agpaitic syenite of the "Mokhnatye Roga" area is extremely enriched in dispersed and rare lithophile elements. The

  4. Eustatic control on early dolomitization of cyclic peritidal carbonates: Evidence from the Early Ordovician Upper Knox Group, Appalachians and Middle to Late Cambrian Bonanza King Formation, southern Great basin

    SciTech Connect

    Montanez, I.P. )

    1991-03-01

    The origin of massive dolomite in ancient cyclic carbonate successions remains a poorly resolved issue reflecting the lack of modern analogs of extensive dolomitization. This paper presents evidence for extensive synsedimentary dolomitization of peritidal cyclic carbonates of the Early Ordovician upper Knox Group, Appalachians, and of the Middle to Late Cambrian Bonanza King Formation, southern Great basin. Early dolomitization of these Cambro-Ordovician carbonates was synchronous with regressive conditions governed by superimposed sea-level oscillations (fifth-, fourth-, and third-order).

  5. Using the Mount Pinatubo Volcanic Eruption to Determine Climate Sensitivity: Comments on "Climate Forcing by the Volcanic Eruption of Mount Pinatubo" by David H. Douglass and Robert S. Knox

    SciTech Connect

    Wigley, T L; Ammann, C M; Santer, B D; Taylor, K E

    2005-04-22

    [1] Douglass and Knox [2005], hereafter referred to as DK, present an analysis of the observed cooling following the 1991 Mt. Pinatubo eruption and claim that these data imply a very low value for the climate sensitivity (equivalent to 0.6 C equilibrium warming for a CO{sub 2} doubling). We show here that their analysis is flawed and their results are incorrect.

  6. Xenoliths of Phl- Ol breccia and lamproite- like dykes in Udachanaya pipe

    NASA Astrophysics Data System (ADS)

    Ashchepkov, Igor; Ntaflos, Theodoros; Samsonov, Gerasim; Mityukhin, Sergei; Khmelnikova, Olga

    2013-04-01

    Probe laser system (analyst S.V. Palessky). The Cpx from the contact zone from the last sample show the incline REE pattern with LREE to 100 and hump near Pr. The incompatible element (IK) are more plat near 70 C1 with depression in Nb -Ta. The REE patterns for phlogopite are more inclined. Phls as well as bulk rock demonstrate inflected in Gd patterns consisting from two highly inclined parts suggesting mixing of two highly evolved liquids. Spiderdiagrams show continuous PhlL enrichment in IK (smaller in HFSE and Pb) and extremely high Ba, Rb (1000C1). The Cr- low garnet megacryst show elevated LREE and high HREE and moderate enrichment in IK. Phl-Ol rocks represent the last stage dyke stage of H2O rich melts evolution close to kimberlite II which produced Phl metasomatism in the lithosphere base (Ashchepkov et al., 2012, 2013). RBRF grant 11-05-00060.

  7. Electromagnetic induction in a conductive strip in a medium of contrasting conductivity: application to VLF and MT above molten dykes

    NASA Astrophysics Data System (ADS)

    Davis, Paul M.

    2014-11-01

    Very low frequency (VLF) electromagnetic waves that penetrate conductive magma-filled dykes generate secondary fields on the surface that can be used to invert for dyke properties. The model used for the interpretation calculates currents induced in a conductive strip by an inducing field that decays exponentially with depth due to the conductivity of the surrounding medium. The differential equations are integrated to give an inhomogeneous Fredholm equation of the second kind with a kernel consisting of a modified Bessel function of the second kind. Numerical methods are typically used to solve for the induced currents in the strip. In this paper, we apply a modified Galerkin-Chebyshev method, which involves separating the kernel into source and field spectra and integrating the source terms to obtain a matrix equation for the unknown coefficients. The incident wave is expressed as a Chebyshev series. The modified Bessel function is separated into a logarithmic singularity and a non-singular remainder, both of which are expanded in complex Chebyshev polynomials. The Chebyshev coefficients for the remainder are evaluated using a fast Fourier transform, while the logarithmic term and incident field have analytic series. The deconvolution then involves a matrix inversion. The results depend on the ratio of strip-size to skin-depth. For infinite skin-depth and a singular conductivity distribution given by τ_0 a/√{a^2 - z^2 } (where τ0 is the conductance, a is the half-length and z the distance from the centre), Parker gives an analytic solution. We present a similar analytic series solution for the finite skin-depth case, where the size to skin depth ratio is small. Results are presented for different ratios of size to skin depth that can be compared with numerical solutions. We compare full-space and half-space solutions. A fit of the model to VLF data taken above a magma filled dykes in Hawaii and Mt Etna demonstrates that while properties such as depth to top

  8. Modelling of The Dyke Emplacement Leading To The Etna July 2001 Eruption Through Continuous Tilt and GPS Data

    NASA Astrophysics Data System (ADS)

    Bonaccorso, A.; Aloisi, M.; Mattia, A.

    During the June 2001 eruption of Mt. Etna the continuous ground deformation mon- itoring have been recorded through tilt (9 stations) and GPS (11 stations) permanent networks. The evolution of the July crisis preceding and leading to the eruption has been monitored through the tilt and GPS continuous measurements, which constrained in time the final intrusion and inferred the position and geometry of the uprising dyke. The tilt signals, which record 48 samples/day, fixed the time action of the intrusion, whose main effects are recorded during 13-15 July in concomitance with the first days of the seismic crisis. In particular, the high precision long-base mercury tiltmeter, in- stalled at Pizzi Deneri observatory in the high north-eastern flank close to the crater area, showed very well the continuous deformation during the dyke emplacement. The deformation pattern, at the entire volcano scale, was well characterised by the daily measurement sessions recorded at the GPS permanent network. The variations recorded at the permanent GPS stations started from July 13 and, in agreement with tilt recordings, were mainly cumulated in the following two days. The GPS measurements showed horizontal displacement vectors much bigger than vertical changes. The defor- mation pattern indicates the response to a tensile mechanisms that appears compatible with an intrusion in the volcano edifice along a ca. N-S direction. In this poster we show the modelling of the marked ground deformation changes recorded in the days before the eruption starting. The first results show that a tensile crack with an opening dislocation of ~3 m. and crossing the entire edifice, south-west to the crater area, can explain the recorded deformation pattern. The location of the modelled tensile source fits the seismogenetic zone characterized by epicenters aligned in a ca. N-S direction with the foci clustered in the last shallow kilometers. The ground deformation pat- tern associated with the final

  9. The French Guyana doleritic dykes: geochemical evidence of three populations and new data for the Jurassic Central Atlantic Magmatic Province

    NASA Astrophysics Data System (ADS)

    Nomade, S.; Pouclet, A.; Chen, Y.

    2002-12-01

    A petrographic and geochemical study of 15 Early Jurassic and 7 Proterozoic dolerites of French Guyana, and of one Jurassic dolerite from Ivory-Coast were carried out. The Early Jurassic SSW-NNE trending dykes have doleritic aphyric or gabbroic phyric texture. Their chemical compositions, slightly under-saturated to over-saturated, show moderate to low Mg-ratios (63-36), high TiO 2 contents (1.85-3.56 wt.%), weak rare earth element fractionation [1.8<(La/Yb) n <4.6], negative Sr-anomalies (0.41dykes were identified in French Guyana. Compared to the Jurassic ones the Proterozoic dykes have NNW-SSE and E-W trending direction, more important LILE enrichment, low TiO 2 contents (<2 wt%) and Nb-Ta negative anomalies. Their calc-alkaline signature could be the result of a previous subduction and may be related to the 1800 Ma Venturi-Tapajós event, which contaminated the mantle source.

  10. Seismic constraints on a large dyking event and initiation of a transform fault zone in Western Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Ahmed, AbdulHakim; Doubre, Cecile; Leroy, Sylvie; Perrot, Julie; Audin, Laurence; Rolandone, Frederique; Keir, Derek; Al-Ganad, Ismael; Sholan, Jamal; Khanbari, Khaled; Mohamed, Kassim; Vergne, Jerome; Jacques, Eric; Nercessian, Alex

    2013-04-01

    In November 2010, a large number of events were recorded by the world seismic networks showing important activity occurring along the western part of the Aden Ridge. West of the Shulka El Sheik fracture zone, events in this large seismic swarm (magnitudes above 5) occurred in a complex area, where the change of both the ridge direction and the bathymetry suggest the propagation of the ridge into a continental lithosphere and the influence of the Afar plume. We combine several sets of data from permanent networks and temporary 3C broad stations installed after the beginning of the event along the southern and eastern coasts of Yemen and Djibouti respectively, we located more than 600 earthquakes with magnitudes ranging from 2.5 to 5.6 that occurred during the first months following the first event. The spatial distribution of the main seismicity reveals a very clear N115° -trending alignment, parallel to the mean direction of the en-echelon spreading segments that form the ridge at this longitude. Half of the events, which represent half of the total seismic energy released during the first months, are located in the central third section of the segment. Here several volcanic cones and recent lava flows observed from bathymetric and acoustic reflectivity data during the Tadjouraden cruise (Audin, 1999, Dauteuil et al., 2001) constitute the sea floor. In addition to this main activity, two small groups of events suggest the activiation of landslides into a large fan and the activity in a volcanic area 50 km due east from the main active zone. The time evolution of the seismicity shows several bursts of activity. Some of them are clearly related to sudden activities within the volcanic areas, when others exhibit horizontal migration of the events, with velocity around ˜ 1 km/h. The time-space evolution of the seismicity clearly reveals the intrusion of dykes associated with magma propagation from the crustal magmatic centres into the rift zone. Taking into account

  11. Dyke leakage localization and hydraulic permeability estimation through self-potential and hydro-acoustic measurements: Self-potential 'abacus' diagram for hydraulic permeability estimation and uncertainty computation

    NASA Astrophysics Data System (ADS)

    Bolève, A.; Vandemeulebrouck, J.; Grangeon, J.

    2012-11-01

    In the present study, we propose the combination of two geophysical techniques, which we have applied to a dyke located in southeastern France that has a visible downstream flood area: the self-potential (SP) and hydro-acoustic methods. These methods are sensitive to two different types of signals: electric signals and water-soil pressure disturbances, respectively. The advantages of the SP technique lie in the high rate of data acquisition, which allows assessment of long dykes, and direct diagnosis in terms of leakage area delimitation and quantification. Coupled with punctual hydro-acoustic cartography, a leakage position can be precisely located, therefore allowing specific remediation decisions with regard to the results of the geophysical investigation. Here, the precise localization of leakage from an earth dyke has been identified using SP and hydro-acoustic signals, with the permeability of the preferential fluid flow area estimated by forward SP modeling. Moreover, we propose a general 'abacus' diagram for the estimation of hydraulic permeability of dyke leakage according to the magnitude of over water SP anomalies and the associated uncertainty.

  12. Paleomagnetism of Devonian dykes in the northern Kola Peninsula and its bearing on the apparent polar wander path of Baltica in the Precambrian

    NASA Astrophysics Data System (ADS)

    Veselovskiy, Roman V.; Bazhenov, Mikhail L.; Arzamastsev, Andrey A.

    2016-04-01

    Mafic dykes and large alkaline and carbonatite intrusions of Middle-Late Devonian age are widespread on the Kola Peninsula in NE Fennoscandia. These magmatic rocks are well characterized with petrographic, geochemical and geochronological data but no paleomagnetic results have been reported yet. We studied dolerite dykes from the northern part of the Peninsula and isolated three paleomagnetic components in these rocks. A low-temperature component is aligned along the present-day field, while a major constituent of natural remanent magnetization is an intermediate-temperature component (Decl. = 79.6°, Inc. = 78.5°, α95 = 5,9°, N = 17 sites) that is present in most Devonian dykes but is found in some baked metamorphic rocks and Proterozoic dykes too. Finally, a primary Devonian component could be reliably isolated from two dykes only. Rock-magnetic studies point to presumably primary low-Ti titanomagnetite and/or pure magnetite as the main remanence carriers but also reveal alteration of the primary minerals and the formation of new magnetic phases. The directions of a major component differ from the Middle Paleozoic reference data for Baltica but closely match those for the 190 ± 10 Ma interval recalculated from the apparent polar wander path of the craton. We assume that this Early Jurassic component is a low-temperature overprint of chemical origin. The main impact of the new results is not to mid-Paleozoic or Early Mesozoic times but to much older epochs. Analysis of paleomagnetic data shows that the directionally similar remanences are present in objects with the ages ranging from 500 Ma to ~ 2 Ga over entire Fennoscandia. Hence we argue that an Early Jurassic remagnetization is of regional extent but cannot link it to a certain process and a certain tectonic event. If true, this hypothesis necessitates a major revision of the APWP for Baltica over a wide time interval.

  13. Impacts of dyke development in flood prone areas in the Vietnamese Mekong Delta to downstream flood hazard

    NASA Astrophysics Data System (ADS)

    Khanh Triet Nguyen, Van; Dung Nguyen, Viet; Fujii, Hideto; Kummu, Matti; Merz, Bruno; Apel, Heiko

    2016-04-01

    The Vietnamese Mekong Delta (VMD) plays an important role in food security and socio-economic development of the country. Being a low-lying coastal region, the VMD is particularly susceptible to both riverine and tidal floods, which provide, on (the) one hand, the basis for the rich agricultural production and the livelihood of the people, but on the other hand pose a considerable hazard depending on the severity of the floods. But despite of potentially hazardous flood, the area remain active as a rice granary due to its nutrient-rich soils and sediment input, and dense waterways, canals and the long standing experience of the population living with floods. In response to both farmers' requests and governmental plans, the construction of flood protection infrastructure in the delta progressed rapidly in the last twenty years, notably at areas prone to deep flooding, i.e. the Plain of Reeds (PoR) and Long Xuyen Quadrangle (LXQ). Triple rice cropping becomes possible in farmlands enclosed by "full-dykes", i.e. dykes strong and high enough to prevent flooding of the flood plains for most of the floods. In these protected flood plains rice can be grown even during the peak flood period (September to November). However, little is known about the possibly (and already alleged) negative impacts of this fully flood protection measure to downstream areas. This study aims at quantifying how the flood regime in the lower part of the VMD (e.g. Can Tho, My Thuan, …) has been changed in the last 2 recent "big flood" events of 2000 and 2011 due to the construction of the full-dyke system in the upper part. First, an evaluation of 35 years of daily water level data was performed in order to detect trends at key gauging stations: Kratie: upper boundary of the Delta, Tan Chau and Chau Doc: areas with full-dyke construction, Can Tho and My Thuan: downstream. Results from the Mann-Kendall (MK) test show a decreasing trend of the annual maximum water level at 3 stations Kratie, Tan

  14. Petrogenesis of Mesoproterozoic lamproite dykes from the Garledinne (Banganapalle) cluster, south-western Cuddapah Basin, southern India

    NASA Astrophysics Data System (ADS)

    Rao, N. V. Chalapathi; Atiullah; Kumar, Alok; Sahoo, Samarendra; Nanda, Purnendu; Chahong, Ngazimpi; Lehmann, B.; Rao, K. V. S.

    2016-04-01

    We report mineral chemistry and whole-rock major and trace-element geochemistry for a recent find of Mesoproterozoic (~1.4 Ga) lamproites from the Garledinne (Banganapalle) cluster, south-western part of the Paleo-Mesoproterozoic Cuddapah Basin, southern India. The Garledinne lamproites occur as WNW-ESE-trending dykes that have undergone varying degree of pervasive silicification and carbonate alteration. Nevertheless, their overall texture and relict mineralogy remain intact and provide important insights into the nature of their magmas. The lamproite dykes have porphyritic to weakly porphyritic textures comprising pseudomorphed olivine macrocrysts and microphenocrysts, titanian phlogopite microphenocrysts, spinel having a compositional range from chromite to rarely magnesiochromite, Sr-rich apatite and niobian rutile. The Garledinne and other Cuddapah Basin lamproites (Chelima and Zangamarajupalle) collectively lack sanidine, clinopyroxene, potassic richterite, and titanite and are thus mineralogically distinct from the nearby Mesoproterozoic lamproites (Krishna and Ramadugu) in the Eastern Dharwar Craton, southern India. The strong correlation between various major and trace elements coupled with high abundances of incompatible and compatible trace elements imply that alteration and crustal contamination have had a limited effect on the whole-rock geochemistry (apart from K2O and CaO) of the Garledinne lamproites and that olivine fractionation played an important role in their evolution. The Garledinne lamproites represent small-degree partial melts derived from a refractory (previously melt extracted) peridotitic mantle source that was subsequently metasomatised (enriched) by carbonate-rich fluids/melts within the garnet stability field. The involvement of multiple reservoirs (sub-continental lithospheric mantle and asthenosphere) has been inferred in their genesis. The emplacement of the Garledinne lamproites is linked to extensional events, across the various

  15. DOH1, a Class 1 knox Gene, Is Required for Maintenance of the Basic Plant Architecture and Floral Transition in Orchid

    PubMed Central

    Yu, Hao; Yang, Shu Hua; Goh, Chong Jin

    2000-01-01

    We report here the isolation and identification of an orchid homeobox gene, DOH1, from Dendrobium Madame Thong-In. Analyses of its sequence and genomic organization suggest that DOH1 may be the only class 1 knox gene in the genome. DOH1 mRNA accumulates in meristem-rich tissues, and its expression is greatly downregulated during floral transition. In situ hybridization analysis demonstrates that DOH1 is also expressed in the incipient leaf primordia and is later detected in the same region of the inflorescence apex, as in DOMADS1. Overexpression of DOH1 in orchid plants completely suppresses shoot organization and development. Transgenic orchid plants expressing antisense mRNA for DOH1 show multiple shoot apical meristem (SAM) formations and early flowering. In addition, both the sense and antisense transformants exhibit defects in leaf development. These findings suggest that DOH1 plays a key role in maintaining the basic plant architecture of orchid through control of the formation and development of the SAM and shoot structure. Investigations of DOMADS1 expression in the SAM during floral transition reveal that the precocious flowering phenotype exhibited by DOH1 antisense transformants is coupled with the early onset of DOMADS1 expression. This fact, together with the reciprocal expression of DOH1 and DOMADS1 during floral transition, indicates that downregulation of DOH1 in the SAM is required for floral transition in orchid and that DOH1 is a possible upstream regulator of DOMADS1. PMID:11090215

  16. Indoor Radon Measurement in Van

    SciTech Connect

    Kam, E.; Osmanlioglu, A. E.; Celebi, N.; Dogan, I.

    2007-04-23

    In this study, indoor radon concentrations obtained from the radon surveys conducted in the Van. Radon monitoring was performed by applying a passive, time-integrating measuring technique. For this purpose, CR-39 nuclear track detectors were installed in dwellings for 2 months. After the monitoring period, detectors were collected. In order to make the alpha tracks visible, chemical etching was applied to the exposed detectors. Nuclear track numbers and the corresponding indoor radon concentrations were determined. Annual effective dose equivalents and the risk probabilities caused by indoor radon inhalation were calculated, and the found results compared with the indoor radon concentrations' data measured in different provinces of Turkey.

  17. Caractérisation géochimique des dykes basiques du massif de les Saras (Mayombe Congolais, Afrique Centrale): conséquences géodynamiquesGeochemical characterizations of basic dykes of the Saras massif (Congolese Mayombe Belt, Central Africa): geodynamic implications

    NASA Astrophysics Data System (ADS)

    Boni, J. Mpemba; Vellutini, P. J.

    1992-02-01

    The Saras granodioritic massif is one of the Eburnean intrusive plutons of the Mayombe Belt. (South-West Congo, Central Africa) It is crosscut by a system of basic dykes, of diversified composition. Petrographic data and a comparative geochemical study, using incompatible trace elements, shows a tholeiitic transitional affinity, and allow us to suggest that these dykes are continental basaltic suites, from extensive areas. This basic magmatism, scattered in the whole Congo Craton, marks a widespread extensional episode in relation with the formation of subsidence basins or true aulacogens, at about 970 Ma (Pan African).

  18. Van Go: A Labor of Love

    ERIC Educational Resources Information Center

    Williams, Jennifer

    2012-01-01

    Like a tapestry woven with one outstanding thread from beginning to end, the author's forty-year tenure as an art educator has its golden thread in her Van Go art outreach project. Quite literally, she takes students in a "van" and they "go," mostly on dirt roads, taking art to rural schools in Idaho, some of which have no more than three students…

  19. Petrology, geochronology and emplacement model of the giant 1.37 Ga arcuate Lake Victoria Dyke Swarm on the margin of a large igneous province in eastern Africa

    NASA Astrophysics Data System (ADS)

    Mäkitie, Hannu; Data, Gabriel; Isabirye, Edward; Mänttäri, Irmeli; Huhma, Hannu; Klausen, Martin B.; Pakkanen, Lassi; Virransalo, Petri

    2014-09-01

    A comprehensive description of the petrography, geochemical composition, Sm-Nd data and intrinsic field relationships of a giant arcuate Mesoproterozoic mafic dyke swarm in SW Uganda is presented for the first time. The swarm is ∼100 km wide and mainly hosted in the Palaeoproterozoic Rwenzori Belt between the Mesoproterozoic Karagwe-Ankole Belt and the Archaean Uganda Block. The dykes trend NW-SE across Uganda, but can be correlated across Lake Victoria to another set of arcuate aeromagnetic anomalies that continue southwards into Tanzania, resulting in a remarkably large semi-circular swarm with an outer diameter of ∼500 km. We propose that this unique giant dyke structure be named the Lake Victoria Dyke Swarm (LVDS). The dykes are tholeiites with Mg numbers between 0.69 and 0.44, and with inherited marked negative Nb and P anomalies in spider diagrams. Two dykes provide Sm-Nd mineral ages of 1368 ± 41 Ma and 1374 ± 42 Ma, with initial εNd values of -2.3 and -3.2, and 87Sr/86Sr ratios of ∼0.706-0.709. Geotectonic discrimination diagrams for the swarm exhibit more arc type than within-plate tectonic signatures, but this is in accordance with systematic enrichments in LREE, U and Th in the dolerites, more likely due to the involvement of the continental lithosphere during their petrogenesis. The LVDS is coeval with a regional ∼1375 Ma bimodal magmatic event across nearby Burundi, Rwanda and NW Tanzania, which can collectively be viewed as a large igneous province (LIP). It also indicates that the nearby Karagwe-Ankole Belt sequences - bracketed between 1.78 and 1.37 Ga and assumed by some to have been deposited within intracratonic basins - were capped by flood basalts that have subsequently been removed by erosion. Different geochemical signatures (e.g. LaN/SmN) suggest that most of the arcuate swarm was derived from an enriched SCLM, whereas related intrusions in the centre of this semi-circular segment have more or less enriched asthenospheric mantle

  20. Petrogenesis and tectonic implications of the Neoproterozoic Datian mafic-ultramafic dykes in the Panzhihua area, western Yangtze Block, SW China

    NASA Astrophysics Data System (ADS)

    Yang, Yi-Jin; Zhu, Wei-Guang; Bai, Zhong-Jie; Zhong, Hong; Ye, Xian-Tao; Fan, Hong-Peng

    2016-03-01

    Mafic-ultramafic dykes are important geological markers that can punctuate the onset of crustal extension during the breakup of a continent and provide valuable information on the mantle source. This study reports secondary ion mass spectroscopy zircon and baddeleyite U-Pb ages, elemental and Nd isotopic data for the Datian mafic-ultramafic dykes in the Panzhihua area, western Yangtze Block, SW China. Two kinds of rocks are confirmed: the picritic rock and the dolerite. Based on petrographic and geochemical features, the dolerite dykes are further subdivided into two groups: Group I mafic and Group II mafic dykes, which emplaced at ~760 Ma (zircon U-Pb) and ~800 Ma (zircon and baddeleyite U-Pb), respectively. All samples from the picritic rocks and the Group I mafic rocks show the features of high-Ti and alkaline basaltic magma in composition as well as "humped" trace element patterns, which are similar to those of typical alkaline basalts associated with continental rifts except for the slightly negative Nb-Ta anomalies. The Group II mafic rocks display the features of low-Ti and tholeiitic magma, moderately enriched in LILE and LREE, and characterized by distinctively negative Nb-Ta anomalies. The primary magmas of the picritic rocks and the Group I mafic rocks were generated from ca 25 % partial melting of an OIB-like, Nd isotopically depleted but incompatible elements relatively enriched mantle source within a garnet stable field. The Group II mafic rocks crystallized from crustal contaminated mafic magmas that were derived from a spinel-bearing sub-continental lithospheric mantle source, because of low ratios of La/Yb, Ti/Y and Sm/Yb. Geochemical features suggest that these groups of mafic-ultramafic dykes were formed in a continental rift setting, but derived from different mantle sources. In combination with other Neoproterozoic igneous rocks in the western margin of Yangtze Block, it is suggested that the Datian mafic-ultramafic dykes in the Panzhihua area

  1. Petrological and geochemical constraints on the origin of mafic dykes intruding the composite Kaçkar Pluton from the eastern Blacksea magmatic arc, NE Turkey

    NASA Astrophysics Data System (ADS)

    Aydin, Faruk; Oguz, Simge; Baser, Rasim; Uysal, Ibrahim; Sen, Cüneyt; Karsli, Orhan; Kandemir, Raif

    2015-04-01

    Geological, petrographical and geochemical data of mafic dykes intruding the composite Kaçkar Pluton from the eastern Blacksea magmatic arc (EBMA), NE Turkey, provide new insights into the nature of the metasomatizing agents in subcontinental lithospheric mantle beneath the region during the late Mesozoic-early Tertiary. Mafic dykes from the Çaykara and Hayrat (Trabzon), and also Ikizdere (Rize) areas from the northern margin of the EBMA consist of basalts, dolerites, lamprophyres (basic member) and lesser basaltic andesites and trachyandesites (evolved member). All dykes have no deformation and metamorphism. The outcrops of these dykes vary, with thickness from 0.2 to 10 m. and visible length from 3 to 20 m. In general, the mafic dykes dip steeply and cut directly across the Kaçkar Pluton, and show NW- and NE-trending, roughly parallel to the orientations of the EBMA main faults. Most of the dyke samples display subaphyric to porphyritic texture with phenocrysts of plagioclase (up to 10%), clinopyroxene (5-20%), amphibole (5-15%), and some contain variable amount of biotite (5-20%), lesser quartz (1-2%), and minor euhedral zircon, apatite and Fe-Ti oxides. The basic members of the mafic dykes have SiO2 of 44.1-51.9%, MgO of 4.5-12.1%, and TiO2 >mostly 0.8% (up to 2.3%) with K2O+Na2O of 1.3-6.6% with mostly subalkaline character. They are relatively high in mg-number (0.45-0.73) and transition metals (V=171-376 ppm, Co=22-45 ppm, Ni=3-148 ppm, and Sc=21-49 ppm). The evolved members of the dykes exhibit relatively higher SiO2 (57.1-60.2%) and K2O+Na2O (5.6-9.0%), and lower MgO (2.2-5.9%) and TiO2 (0.5-0.8%) contents than those from the basic dykes. Also, these samples have slightly low mg-number (0.41-0.65) and transition metals (V=99-172 ppm, Co=9-22 ppm, Ni=1-43 ppm, and Sc=9-20 ppm). In the Harker diagrams, all samples of the mafic dykes form a continuous array, and exhibit similar geochemical characteristics. In general, SiO2 inversely correlates with MgO, Fe

  2. Detection of both vanA & vanB genes in vanA phenotypes of Enterococci by Taq Man RT-PCR

    PubMed Central

    Mirzaei, Bahman; Babaei, Ryhane; Asiabar, Akbar Pour Dadash; Bameri, Zakaria

    2015-01-01

    Twenty seven isolates of vancomycin resistant Enterococci based on the disk diffusion and E- test have been screened; being found eight (0.3%) clinical isolates of vanA & vanB through Taq Man Real Time PCR assay. This study shows the presence of both vanA & vanB genotypes in vanA phenotypes clinical isolates in the three hospitals in Iran. PMID:26221103

  3. The peach (Prunus persica L. Batsch) genome harbours 10 KNOX genes, which are differentially expressed in stem development, and the class 1 KNOPE1 regulates elongation and lignification during primary growth

    PubMed Central

    Giannino, Donato

    2012-01-01

    The KNOTTED-like (KNOX) genes encode homeodomain transcription factors and regulate several processes of plant organ development. The peach (Prunus persica L. Batsch) genome was found to contain 10 KNOX members (KNOPE genes); six of them were experimentally located on the Prunus reference map and the class 1 KNOPE1 was found to link to a quantitative trait locus (QTL) for the internode length in the peach×Ferganensis population. All the KNOPE genes were differentially transcribed in the internodes of growing shoots; the KNOPE1 mRNA abundance decreased progressively from primary (elongation) to secondary growth (radial expansion). During primary growth, the KNOPE1 mRNA was localized in the cortex and in the procambium/metaphloem zones, whereas it was undetected in incipient phloem and xylem fibres. KNOPE1 overexpression in the Arabidopsis bp4 loss-of-function background (35S:KNOPE1/bp genotype) restored the rachis length, suggesting, together with the QTL association, a role for KNOPE1 in peach shoot elongation. Several lignin biosynthesis genes were up-regulated in the bp4 internodes but repressed in the 35S:KNOPE1/bp lines similarly to the wild type. Moreover, the lignin deposition pattern of the 35S:KNOPE1/bp and the wild-type internodes were the same. The KNOPE1 protein was found to recognize in vitro one of the typical KNOX DNA-binding sites that recurred in peach and Arabidopsis lignin genes. KNOPE1 expression was inversely correlated with that of lignin genes and lignin deposition along the peach shoot stems and was down-regulated in lignifying vascular tissues. These data strongly support that KNOPE1 prevents cell lignification by repressing lignin genes during peach stem primary growth. PMID:22888130

  4. A MADS-box gene NtSVP regulates pedicel elongation by directly suppressing a KNAT1-like KNOX gene NtBPL in tobacco (Nicotiana tabacum L.)

    PubMed Central

    Wang, Di; Chen, Xiaobo; Zhang, Zenglin; Liu, Danmei; Song, Gaoyuan; Kong, Xingchen; Geng, Shuaifeng; Yang, Jiayue; Wang, Bingnan; Wu, Liang; Li, Aili; Mao, Long

    2015-01-01

    Optimal inflorescence architecture is important for plant reproductive success by affecting the ultimate number of flowers that set fruits and for plant competitiveness when interacting with biotic or abiotic conditions. The pedicel is one of the key contributors to inflorescence architecture diversity. To date, knowledge about the molecular mechanisms of pedicel development is derived from Arabidopsis. Not much is known regarding other plants. Here, an SVP family MADS-box gene, NtSVP, in tobacco (Nicotiana tabacum) that is required for pedicel elongation was identified. It is shown that knockdown of NtSVP by RNA interference (RNAi) caused elongated pedicels, while overexpression resulted in compact inflorescences with much shortened pedicels. Moreover, an Arabidopsis BREVIPEDECELLUS/KNAT1 homologue NtBP-Like (NtBPL) was significantly up-regulated in NtSVP-RNAi plants. Disruption of NtBPL decreased pedicel lengths and shortened cortex cells. Consistent with the presence of a CArG-box at the NtBPL promoter, the direct binding of NtSVP to the NtBPL promoter was demonstrated by yeast one-hybrid assay, electrophoretic mobility shift assay, and dual-luciferase assay, in which NtSVP may act as a repressor of NtBPL. Microarray analysis showed that down-regulation of NtBPL resulted in differential expression of genes associated with a number of hormone biogenesis and signalling genes such as those for auxin and gibberellin. These findings together suggest the function of a MADS-box transcription factor in plant pedicel development, probably via negative regulation of a BP-like class I KNOX gene. The present work thus postulates the conservation and divergence of the molecular regulatory pathways underlying the development of plant inflorescence architecture. PMID:26175352

  5. BJ-1108, a 6-Amino-2,4,5-Trimethylpyridin-3-ol Analog, Inhibits Serotonin-Induced Angiogenesis and Tumor Growth through PI3K/NOX Pathway

    PubMed Central

    Banskota, Suhrid; Gautam, Jaya; Regmi, Sushil C.; Gurung, Pallavi; Park, Myo-Hyeon; Kim, Seung Joo; Nam, Tae-gyu; Jeong, Byeong-Seon; Kim, Jung-Ae

    2016-01-01

    5-Hydroxytryptamine (5-HT) induces proliferation of cancer cells and vascular cells. In addition to 5-HT production by several cancer cells including gastrointestinal and breast cancer, a significant level of 5-HT is released from activated platelets in the thrombotic environment of tumors, suggesting that inhibition of 5-HT signaling may constitute a new target for antiangiogenic anticancer drug discovery. In the current study we clearly demonstrate that 5-HT-induced angiogenesis was mediated through the 5-HT1 receptor-linked Gβγ/Src/PI3K pathway, but not through the MAPK/ERK/p38 pathway. In addition, 5-HT induced production of NADPH oxidase (NOX)-derived reactive oxygen species (ROS). In an effort to develop new molecularly targeted anticancer agents against 5-HT action in tumor growth, we demonstrate that BJ-1108, a derivative of 6-amino-2,4,5-trimethylpyridin-3-ol, significantly inhibited 5-HT-induced angiogenesis. In addition, BJ-1108 induced a significant reduction in the size and weight of excised tumors in breast cancer cell-inoculated CAM assay, showing proportionate suppression of tumor growth along with inhibition of angiogenesis. In human umbilical vein endothelial cells (HUVECs), BJ-1108 significantly suppressed 5-HT-induced ROS generation and phosphorylation of PI3K/Akt but not of Src. Unlike NOX inhibitors, BJ-1108, which showed better antioxidant activity than vitamin C, barely suppressed superoxide anion induced by mevalonate or geranylgeranyl pyrophosphate which directly activates NOX without help from other signaling molecules in HUVECs, implying that the anti-angiogenic action of BJ-1108 was not mediated through direct action on NOX activation, or free radical scavenging activity. In conclusion, BJ-1108 inhibited 5-HT-induced angiogenesis through PI3K/NOX signaling but not through Src, ERK, or p38. PMID:26824764

  6. A MADS-box gene NtSVP regulates pedicel elongation by directly suppressing a KNAT1-like KNOX gene NtBPL in tobacco (Nicotiana tabacum L.).

    PubMed

    Wang, Di; Chen, Xiaobo; Zhang, Zenglin; Liu, Danmei; Song, Gaoyuan; Kong, Xingchen; Geng, Shuaifeng; Yang, Jiayue; Wang, Bingnan; Wu, Liang; Li, Aili; Mao, Long

    2015-10-01

    Optimal inflorescence architecture is important for plant reproductive success by affecting the ultimate number of flowers that set fruits and for plant competitiveness when interacting with biotic or abiotic conditions. The pedicel is one of the key contributors to inflorescence architecture diversity. To date, knowledge about the molecular mechanisms of pedicel development is derived from Arabidopsis. Not much is known regarding other plants. Here, an SVP family MADS-box gene, NtSVP, in tobacco (Nicotiana tabacum) that is required for pedicel elongation was identified. It is shown that knockdown of NtSVP by RNA interference (RNAi) caused elongated pedicels, while overexpression resulted in compact inflorescences with much shortened pedicels. Moreover, an Arabidopsis BREVIPEDECELLUS/KNAT1 homologue NtBP-Like (NtBPL) was significantly up-regulated in NtSVP-RNAi plants. Disruption of NtBPL decreased pedicel lengths and shortened cortex cells. Consistent with the presence of a CArG-box at the NtBPL promoter, the direct binding of NtSVP to the NtBPL promoter was demonstrated by yeast one-hybrid assay, electrophoretic mobility shift assay, and dual-luciferase assay, in which NtSVP may act as a repressor of NtBPL. Microarray analysis showed that down-regulation of NtBPL resulted in differential expression of genes associated with a number of hormone biogenesis and signalling genes such as those for auxin and gibberellin. These findings together suggest the function of a MADS-box transcription factor in plant pedicel development, probably via negative regulation of a BP-like class I KNOX gene. The present work thus postulates the conservation and divergence of the molecular regulatory pathways underlying the development of plant inflorescence architecture. PMID:26175352

  7. Mesoproterozoic mafic and carbonatitic dykes from the northern margin of the North China Craton: Implications for the final breakup of Columbia supercontinent

    NASA Astrophysics Data System (ADS)

    Yang, Kui-Feng; Fan, Hong-Rui; Santosh, M.; Hu, Fang-Fang; Wang, Kai-Yi

    2011-01-01

    The North China Craton (NCC) has figured prominently in recent reconstructions on the Paleoproterozoic supercontinent Columbia. Here we report abundant carbonatitic and mafic dykes from around the giant Bayan Obo rare earth element deposit in the northern margin of the NCC, and present geochemical and isotope geochronological data. The carbonatite (1354 ± 59 Ma) and mafic dykes (1227 ± 60 Ma) have comparable whole rock Sm-Nd isochron ages and Sr-Nd isotope compositions, suggesting a common source characteristic. Their geochemical characters including major and trace elements as well as REE patterns also attest to a common tectonic environment of magma generation and emplacement within a continental margin rift. The extensive mafic and carbonatitic magmatisms are associated with an extensional event that resulted in the formation of the Bayan Obo rift in the northern margin of the NCC, which we correlate with the final stages of fragmentation of the Columbia supercontinent amalgam.

  8. Sheeted and bulbous pluton intrusion mechanisms of a small granitoid from southeastern Australia: implications for dyke-to-pluton transformation during emplacement

    NASA Astrophysics Data System (ADS)

    Fowler, T. J.

    1994-06-01

    The small late syn-tectonic Carboniferous Davys Creek Granite (DCG) of southeastern Australia consists of microgranitic intrusive bodies of diverse geometry and structure. These bodies include: (1) subvertical concordant sheets; (2) bulbous peneconcordant plutons with apophyses and discordant lobes; and (3) subvertical dykes and stocks. The sequence of changing intrusive style is broadly 1-2-3. Transition from 1 to 2 was probably a response to rising magma pressures or declining tectonic stresses. The λ parameter of Emerman and Marrett (1990), which discriminates between stable sheet-like and potential stock/pluton/batholith emplacement modes, adequately predicts the transitions between sheet and pluton emplacements for the DCG. Ductile dyking along actively forming foliations appears to have been an important early intrusive mechanism. A transition from sheet to bulbous pluton intrusion style is suggested to have been in response to magma pressure increases.

  9. Contribution of the FUTUREVOLC project to the study of segmented lateral dyke growth in the 2014 rifting event at Bárðarbunga volcanic system, Iceland

    NASA Astrophysics Data System (ADS)

    Sigmundsson, Freysteinn; Hooper, Andrew; Hreinsdóttir, Sigrún; Vogfjörd, Kristín S.; Ófeigsson, Benedikt; Rafn Heimisson, Elías; Dumont, Stéphanie; Parks, Michelle; Spaans, Karsten; Guðmundsson, Gunnar B.; Drouin, Vincent; Árnadóttir, Thóra; Jónsdóttir, Kristín; Gudmundsson, Magnús T.; Samsonov, Sergey; Brandsdóttir, Bryndís; White, Robert S.; Ágústsdóttir, Thorbjörg; Björnsson, Helgi; Bean, Christopher J.

    2015-04-01

    The FUTUREVOLC project (a 26-partner project funded by FP7 Environment Programme of the European Commission, addressing topic "Long-term monitoring experiment in geologically active regions of Europe prone to natural hazards: the Supersite concept) set aims to (i) establish an innovative volcano monitoring system and strategy, (ii) develop new methods for near real-time integration of multi-parametric datasets, (iii) apply a seamless transdisciplinary approach to further scientific understanding of magmatic processes, and (iv) to improve delivery, quality and timeliness of transdisciplinary information from monitoring scientists to civil protection. The project duration is 1 October 2012 - 31 March 2016. Unrest and volcanic activity since August 2014 at one of the focus areas of the project in Iceland, at the Bárðarbunga volcanic system, near the middle of the project duration, has offered unique opportunities for this project. On 16 August 2014 an intense seismic swarm started in Bárðarbunga, the beginning of a major volcano-tectonic rifting event forming over 45 km long dyke extending from the caldera to Holuhraun lava field outside the northern margin of Vatnajökull. A large basaltic, effusive fissure eruption began in Holuhraun on 31 August which had by January formed a lava field with a volume in excess of one cubic kilometre. We document how the FUTUREVOLC project has contributed to the study and response to the subsurface dyke formation, through increased seismic and geodetic coverage and joint interpreation of the data. The dyke intrusion in the Bárðarbunga volcanic system, grew laterally for over 45 km at a variable rate, with an influence of topography on the direction of propagation. Barriers at the ends of each segment were overcome by the build-up of pressure in the dyke end; then a new segment formed and dyke lengthening temporarily peaked. The dyke evolution, which occurred over 14 days, was revealed by propagating seismicity, ground

  10. Occurrence of the vancomycin-resistant genes vanA, vanB, vanCl, vanC2 and vanC3 in Enterococcus strains isolated from poultry and pork.

    PubMed

    Lemcke, R; Bülte, M

    2000-09-25

    It is suspected that the use of avoparcin as a feeding antibiotic for the fat stock contributes to development of cross-resistance against vancomycin and teicoplanin. After isolating enterococci strains from poultry and pork meat by cultivation on citrate azide Tween carbonate agar (CATC) and screening the vancomycin resistance on Columbia colistin nalidixic acid agar (CNA, supplemented with 5% sheepblood and 5 mg vancomycin/l) the polymerase chain reaction (PCR) was used for the detection of the vancomycin resistance genes vanA ('high level'), vanB ('moderate high level'), vanC1, vanC2 and vanC3 ('low level'). Out of 1643 E.-isolates from 115 poultry and 50 pork samples, 420 isolates could be identified as vancomycin resistant, 202 isolates of which carry the vanA, one isolate both the vanA and the vanC1, 38 isolates the vanC1, 14 isolates the vanC2, nine isolates both the vanC1 and the vanC3 gene and 156 isolates carry no gene. The vanB gene was not found in these isolates. Comparing vanA-positive food isolates with those from different human sources by means of the pulsed field gel electrophoresis (PFGE) it could clearly be demonstrated that they do not show homological fingerprints according to the source of origin. It is therefore unlikely that there is a close genetic relationship between isolates from animal foodstuff and humans. PMID:11016608