bluuebunny/crossref_metadata_2025 huggingface dataset:
Broadside wide-angle seismic studies and three-dimensional structure of the crust in the southeast Canadian Cordillera
Authors: Burianyk M. J. A. , Kanasewich E. R. , Udey N.
Published: April 2010

Broadside, or fan, recordings of a Lithoprobe seismic refraction – wide-angle reflection experiment in the southeastern Canadian Cordillera show several features further illuminating the crustal structure beyond that previously derived from SCoRE '90 (Southern Cordillera Refraction Experiment of 1990) in-line data. Analysis of a nearly in-line profile centred on Castlegar, British Columbia, shows lower velocities in the upper crust associated with the Purcell Anticlinorium as well as velocity variations that may have some association with the Purcell fault zone. The depth to Moho is almost 38 km, somewhat deeper and on trend with the structure that has been established farther north. The broadside records show high signal-to-noise ratio PmP arrivals (i.e., reflections from the bottom of the crust). These PmP fan picks were analysed in regions away from in-line profiles, providing further measurements of the depth to Moho in the southeastern Cordillera. The analysis of the broadside records combined with the earlier in-line interpretations as well as older crustal seismic measurements make up a relatively high resolution database, compared with most other regions in Canada, from which we have generated maps of depth to Moho and average crustal velocity in the southeastern Cordillera of Canada. The maps show thin, low-velocity crust over much of the region and indicate a high degree of correlation between current crustal seismic properties and regional isotherms.
Interpretation of seismic reflection and gravity profile data in western Lake Superior
Authors: Sexton John L. , Henson Jr. Harvey
Published: April 2010

The interpretation of 1047 km of seismic reflection data collected in western Lake Superior is presented along with reflection traveltime contour maps and gravity models to understand the overall geometry of the Midcontinent Rift System beneath the lake. The Douglas, Isle Royale, and Keweenaw fault zones, clearly imaged on the seismic profiles, are interpreted to be large offset detachment faults associated with initial rifting. These faults have been reactivated as reverse faults with 3–5 km of throw. The Douglas Fault Zone is not directly connected with the Isle Royale Fault Zone. The seismic data has imaged two large basins filled with more than 22 km of middle Keweenawan pre-Portage Lake and Portage Lake volcanic rocks and up to 8 km of upper Keweenawan Oronto and Bayfield sedimentary rocks. These basins persisted throughout Keweenawan time and are separated by a ridge of Archean rocks and a narrow trough bounded by the Keweenaw Fault Zone to the south. Another fault zone, herein named the Ojibwa fault zone, previously interpreted as the northeastern extension of the Douglas Fault Zone, has been reinterpreted as a reverse fault that closely follows the ridge of Archean rocks. Previous researchers have stated that neighboring segments of the rift display alternating polarity of basins associated with large detachment faults. Accommodation zones have been previously interpreted to exist between rift segments; however, the seismic data do not image a clearly identifiable accommodation zone separating the two basins in western Lake Superior. Thus, the seismic profile may lie directly above the pivot of a scissors-type accommodation fault zone, there is no vertical offset associated with the zone, or the zone does not exist. Seismic data interpretations indicate that application of a simple alternating polarity basin – accommodation zone model is an oversimplification of the complex geological structures associated with the Midcontinent Rift System.
Terrestrial heat flow in Lake Superior
Authors: Hart S. R. , Steinhart J. S. , Smith T. J.
Published: April 2010

Using oceanographic heat-flow techniques, 162 measurements of heat flow were made in Lake Superior during the summers of 1966 and 1967. These data are of high quality, with precisions with respect to intercomparisons typically in the 3–5% range. The data define two very clear features. One is a trough of low heat-flow values, which runs continuously for 650 km along the northern edge of the lake, with values ranging between 0.46 and 0.98 heat-flow units (HFU) (19.2–41.0 mW/m2). This feature correlates with surface exposure of Keweenawan mafic volcanics; it is believed to delineate a major crustal separation associated with the Midcontinent Rift and is filled to crustal thicknesses with mafic intrusives and extrusives. This feature has not been imaged with the seismic reflection profiling of GLIMPCE. The other heat-flow feature is an arcuate ridge of high heat-flow values (1.0–1.45 HFU; 41.8–60.7 mW/m2), parallel to and south of the heat-flow trough. The highest areas of this ridge correspond to areas of thick rift-filling Keweenawan sediments. The high heat flow is modulated to lower values in areas where the thick sediments overlie highly thinned crust now containing large thicknesses of mafic volcanic rock. The heat-flow features show very good correlation with the magnetic anomaly map of Lake Superior, but only spotty correlation with the Bouguer gravity anomaly features.
Seismic reflection profiles across the central Kapuskasing uplift
Authors: Leclair Alain D. , Percival John A. , Green Alan G. , Wu Jianjun , West Gordon F. , Wang Weizhong
Published: April 2010

The central Superior Province is transected by the intracratonic Kapuskasing uplift, which contains rocks exhumed from 30 to 35 km paleodepth. As part of the Lithoprobe Kapuskasing transect, approximately 52 km of 16 s seismic reflection data were collected in the central segment of the uplift along three profiles that traverse the northern Groundhog River block, the bounding Saganash Lake fault, and the eastern Val Rita block. The seismic sections have the following characteristics in common: (i) a complexly reflective uppermost portion (< 1 s) limiting correlation of reflective zones and surface features; (ii) numerous subhorizontal, east- and west-dipping reflection zones; and (iii) a significant reduction in reflectivity beyond the refraction-defined Moho (~ 14 s). Beneath the Groundhog River block a series of straight, west-dipping (~ 20°) reflection zones between 2 and 10 s is underlain by subhorizontal reflections in the lower crust. Across the Saganash Lake fault, the Val Rita block is characterized by a maze of discontinuous, curvilinear reflections with general easterly dip down to 8 – 10 s, below which west-dipping events are prominent. A north–south cross profile reveals a highly reflective crust with dominantly horizontal reflection geometry below the Saganash Lake metavolcanic belt, and a steep truncation of reflection zones down to at least 7 s, which correlates with the surface trace of the Nansen Creek fault. This fault resembles well-known strike-slip faults in intraplate settings. The Saganash Lake fault, variably interpreted as a west-side-down normal fault with up to 15 km of throw or a major strike-slip zone, may be visible as a west-dipping, weakly reflective zone steeply truncating east-dipping reflections and becoming listric at depth. This interpretation accords with surface geological observations and gravity models for the structural geometry of the region in which the Groundhog River block is a thin thrust sheet of granulite perched on Abitibi belt rocks and truncated on the west by the crustal-scale Saganash Lake fault. Alternatively, the fault could be a seismically unresolved major transcurrent structure juxtaposing blocks with disparate reflection patterns in the upper 8 s. Limited amounts of late strike-slip motion have been inferred from various geophysical studies.
Ramp-flat geometry within the central Kapuskasing uplift? Evidence from potential field modeling results
Authors: Atekwana E. A. , Salisbury M. H. , Verhoef J. , Culshaw N.
Published: April 2010

Potential field data constrained by seismic reflection, seismic refraction, geologic, and physical-properties data have been used to study the deep crustal structure of the central Kapuskasing uplift. The Val Rita block is interpreted as a thrust sheet of granulites detached at mid-crustal depths and uplifted along a ramp producing an arched, double granulite layer. A thin thrust sheet of southward-thickening granulites best describes the Groundhog River block, whereas simple thrusting along a ramp characterizes the Chapleau block. From this interpretation, a sequential evolution of the Kapuskasing uplift is proposed.At about 2450 Ma, northwest–southeast compression (σ1) resulted in variable thrusting along the Ivanhoe Lake fault zone. This was followed by a period of normal faulting, resulting in the juxtaposition of high- and low-pressure rocks across the Lepage and Saganash Lake faults, with possible truncation of the Val Rita block arch. Further rotation of σ1 to an east–west direction resulted in the reactivation of the Lepage and Saganash Lake faults as dextral transcurrent or transpressional faults accentuating the Val Rita block as an en echelon fold, and distorting the Matachewan dykes. Later (about 2140 Ma), rotation of σ1 into a southwest–northeast direction brought transpression to a halt and a period of intermittent dyke and carbonatite intrusion was initiated, which lasted to about 1200 Ma or just prior to the Grenville orogeny.
Structural correlation within the Kapuskasing uplift
Authors: Bursnall J. T. , Leclair A. D. , Moser D. E. , Percival J. A.
Published: April 2010

Comparison of progressive deformation and metamorphic history within and between the tectonic domains of the Kapuskasing uplift indicates significant variation in age and style of deformation across this large segment of the central Superior Province; multiple stages of tonalite and granitoid intrusion, melt generation, polyphase diachronous deformation, and likely rapid deep burial of supracrustal rocks collectively produced the complex character of this example of Archean mid to deep crust. At least four Archean deformation phases are recognized, although not all are of regional extent. Dated structural chronology suggests that the locus of the earliest recorded deformations migrated to deeper crustal levels with time. Pre-2680 Ma deformation (local D1–D2) within high-level tonalites is correlated with deformation in the Michipicoten supracrustal belt. The apparent earliest deformational fabrics at deeper crustal levels in the granulite terrane of the Kapuskasing structural zone occurred between 2660 and 2640 Ma. Archean third and fourth phase deformation phases (~ 2667 to ~ 2629 Ma) are present at mid-crustal and deeper levels and deform post-2667 Ma metaconglomerate; these resulted in large-scale folding and subhorizontal ductile shear zones, which seem to represent an important transitional zone that separated a passive upper crust from continued ductile strain at deeper levels.Subsequent uplift of the high-grade rocks was accomplished in multiple stages, initiated prior to 2.45 Ga and likely culminated around 1.9 Ga, although continued movement occurred as late as 1.14 Ga. The Ivanhoe Lake fault zone, along which much of the uplift must have occurred, exhibits some evidence of ductile deep-thrust-related fabrics, but most of the observed structures are brittle to brittle–ductile and steeply inclined. A broad zone of pervasive cataclasis and brittle–ductile shear zones is a characteristic feature of the fault zone throughout its length, and both dextral and sinistral offset are locally present. Clear ground evidence for major transcurrent or thrust displacements, however, has not been recognized.
Quantification of lower crustal synmetamorphic fluid fluxes in the Kapuskasing structural zone based on oxygen-isotope profiles across two paragneiss – mafic gneiss contacts
Authors: Puris Eriks M. , Wickham Stephen M.
Published: April 2010

Detailed oxygen-isotope profiles were measured across two very similar amphibolite-grade, paragneiss – mafic gneiss contacts located 2 km apart within the Kapuskasing structural zone. The first profile is asymmetrical about die contact. δ18O values for whole rocks and minerals are homogeneous in the paragneiss (whole-rock δ18O = +10.4 to +11.4‰), smoothly decrease by about 2‰ over 2.5 m moving into the mafic gneiss, and are homogeneous in the remainder of the mafic gneiss (whole-rock δ18O = +7.0 to +7.4‰). The second profile is flat, with homogeneous whole-rock and mineral δ18O values in bom lithologies, and mafic gneiss values (whole-rock δ18O = +8.7 to +9.8‰) that are higher by about 3‰ relative to typical mafic gneiss values. Mineral–mineral isotopic fractioations are fairly constant in all samples and are typical of high-grade metamorphic rocks. Despite their differences, both profiles can be explained by the advection of a mixed H2O–CO2 fluid in equilibrium with the paragneiss across the contact into the mafic gneiss, coupled with diffusion of oxygen in the fluid. Modeling constrains the net fluid flux required to form me first profile to be 1–3 m3/m2, and for me second profile to be ≥ 10 m3/m2. Thus the net fluid flux during metamorphism varied probably by at least a factor of five over 2 km. These fluxes could have been generated locally within the Kapuskasing structural zone during metamorphism either by metamorphic devolatilization reactions or by the release of volatiles from crystallizing magmas.
Thermobarometry of garnet–clinopyroxene–hornblende granulites from the Kapuskasing structural zone
Authors: Mäder Urs K. , Percival John A. , Berman Robert G.
Published: April 2010

Amphibole mixing properties and standard state properties for the end members tremolite, tschermakite, pargasite, ferrotremolite, ferrotschermakite, and ferropargasite have been refined through analysis of relevant phase equilibrium experiments, coexisting cummingtonite–hornblende pairs, and natural mineral parageneses. When merged with the mineral properties given by R.G. Berman, these amphibole properties allow the calculation of numerous equilibria suitable for thermobarometry in a wide range of bulk compositions at amphibolite to granulite metamorphic grades. The method was applied to texturally equilibrated garnet–pyroxene–hornblende gneisses and compared both to results based on anhydrous assemblages and to those for garnet–biotite gneisses from the Kapuskasing structural zone. Thermometer resetting is apparent only in garnet–biotite gneisses, whereas touching garnet–pyroxene pairs in mafic gneiss show little evidence of retrograde Fe–Mg exchange. Computed metamorphic temperatures (garnet–clinopyroxene) for the 50 km wide garnet–clinopyroxene zone, in the range 750–790 °C, show no systematic variation with distance from the Ivanhoe Lake fault zone. Paleopressures computed from hydrous and anhydrous equilibria consistently indicate a north-trending high of 10–11 kbar (1 kbar = 100 MPa), decreasing to 3.3 kbar 60 km to the west in the Wawa gneiss domain. The pressure results define west-dipping Archean isobars with gentle (< 5°) attitudes through the Wawa gneiss domain and steeper dips (~ 17°) east of the amphibolite–granulite transition. The preserved record of high temperatures and pressures and moderate water activities (0.2–0.45) through a prolonged period of lower crustal residence and slow cooling indicated by zircon and titanite geochronology is difficult to reconcile at present.
Rb–Sr biotite and whole-rock data from the Kapuskasing uplift and their bearing on the cooling and exhumation history
Authors: Percival J. A. , Peterman Z. E.
Published: April 2010

Rb–Sr isotopic ratios were measured on biotite and whole rocks from a suite of 21 granitoid rocks from the southern Kapuskasing uplift. Results of 18 of the whole-rock analyses fall on an isochron with an age of 2.677 ± 0.057 Ga and Sri = 0.70080. Biotite model ages range from 2.50 to 1.93 Ga in a general spatial relationship of decreasing age with depth in the structural section as calibrated with the igneous hornblende barometer for tonalitic rocks and garnet–pyroxene barometers for granulites. Near the Michipicoten belt in the west, biotite ages of ~ 2 Ga reflect disturbances also recorded by paleomagnetic and whole-rock Rb–Sr systems. To the east, in a 70 km long northwest–southeast transect toward the Ivanhoe Lake fault zone, ages decrease from 2.50 to 1.95 Ga. In a southern transect ages are in the range 2.30–2.38 Ga to within 15 km of the fault, reflecting consistent erosion levels corresponding to ~ 0.53 MPa, but decrease to 1.93 Ga to the east, in concert with paleopressures in the 0.7–1.0 GPa range.A plateau of low Rb–Sr biotite dates is not evident, suggesting that the Kapuskasing uplift event exposed a frozen-in cooling profile, rather than setting the Rb–Sr clock by rapid cooling of the rocks from above their closure temperature. The youngest biotite date of 1.93 Ga therefore provides a maximum age for uplift, consistent with paleomagnetic data from Archean rocks and Early Proterozoic dykes, but in conflict with some K–Ar and 40Ar/39Ar biotite age data.
Synopsis of paleomagnetic studies in the Kapuskasing structural zone
Authors: Symons D. T. A. , Lewchuk M. T. , Dunlop D. J. , Costanzo-Alvarez V. , Halls H. C. , Bates M. P. , Palmer H. C. , Vandall T. A.
Published: April 2010

This paper summarizes results from paleomagnetic studies sponsored by Lithoprobe on the Kapuskasing structural zone (KSZ). Data from Archean rocks outside the KSZ indicate that the Wawa Subprovince has not been significantly rotated or translated (< 5°) relative to the Abitibi Subprovince. Results from the granulites and amphibolites indicate that the KSZ underwent several kilometres of uplift at ca. 2.51 Ga and then 10 ± 5° west-northwest tilt with several kilometres of further uplift between 2.04 and 1.88 Ga from thrust faulting on the Ivanhoe Lake fault zone. Localized chemical remagnetization occurred at 1.1 Ga along the west side of the Shawmere anorthosite. Paleomagnetic data from the 2.45 Ga Matachewan diabase dike swarm indicate that it was emplaced within one reversed to normal polarity interval of less than 5 Ma. Their polarity pattern indicates major north-trending faults with several kilometres of dip-slip displacement. Their remanence confirms that the Superior Province was deformed around the KSZ into an oroclinal flexure with 40° changes in trend between 2.04 and 1.88 Ga. Results from eight 1.1 Ga alkali syenite–carbonatite complexes show that the KSZ and adjacent subprovinces have undergone only minor uplift (< 6 ± 2 km) since emplacement. Also, these data refine the radiometric ages of some complexes, demonstrate that the use of superchrons to correlate Keweenawan units in the Midcontinental Rift is unsound, and show that Keweenawan magnetic field was symmetrical. Many specific conclusions that relate to a given unit or limited area were drawn in the KSZ paleomagnetic studies.
Finite-element models of evolution for the Kapuskasing structural zone
Authors: Parphenuk Olga I. , Dechoux Véronique , Mareschal Jean-Claude
Published: April 2010

Finite-element modeling was used to assess the conditions for the feasibility of a mechanism of evolution for the Kapuskasing structural zone. The proposed mechanism calls for formation of the Kapuskasing structural zone during an intracratonic shortening event which led to overthrusting in the brittle upper crust and formation of a crustal root by ductile deformation in the lower crust. Simple calculations show that, during overthrusting, the temperature in the lower crust is high and the effective viscosity of rocks could be reduced to 1021–1022 Pa∙s for 10−14 s−1 strain rate. The viscosity of the upper mantle below the Moho is higher by 1 to 2 orders of magnitude. The actual shortening could have been completed in 4–20 Ma at a rate on the order of 0.5–2.5 cm∙a−1, which leads to strain rates consistent with the assumed effective viscosity and to a geologically reasonable level of stress [Formula: see text]. The exposure of different crustal levels by erosion was already underway at the end of the shortening event. The calculations show that the formation of a crustal root by ductile flow in the lower crust requires the viscosity to be higher than 1020 Pa∙s; less viscous material will flow and not produce the observed crustal thickening. The preservation of the crustal root is possible provided that the mantle rheology is much stronger than that of the lower crust. The Moho temperature should have been around 800 °C for the formation and preservation of the root to be possible. Such temperature conditions are compatible with the thermal regime of this part of the Canadian Shield between 2.0 and 2.5 Ga, as estimated from present heat-flow data.
Three-dimensional seismic crustal structure of the Monashee hinterland core complex on the Lithoprobe Southern Canadian Cordillera Transect
Authors: Vasudevan Kris , Cook Frederick A. , Maier Rolf
Published: April 2010

Three-dimensional seismic coverage in an approximately 12 km × 12 km area of the southern Monashee metamorphic complex in the south-central portion of the Canadian Cordillera reveals a complex geometry to the Mesozoic–early Tertiary contractional Monashee décollement. Data were acquired as part of the Lithoprobe Southern Canadian Cordillera Transect where two approximately perpendicular lines intersected on the south flank of the Monashee mountains in the hinterland of the Cordillera. Stacks of traces within 100 m × 100 m bins are nominally 6-fold, but range from zero to 108-fold due to the crooked nature of the lines. Both migrated and unmigrated data have been examined for interpretation, but the highly variable data quality and discontinuous reflectivity cause excessive added noise during the migration process.
Electrical conductivity structure of the Purcell Anticlinorium in southeast British Columbia and northwest Montana
Authors: Gupta Jagdish C. , Jones Alan G.
Published: April 2010

Magnetotelluric data from almost 200 sites were acquired by a commercial contractor over the Precambrian Purcell Anticlinorium west of the Rocky Mountains of Canada and the United States. Fifteen east–west profiles cross the anticlinorium between latitudes of 48 and 49.5°N, and provide a grid suitable for a regional three-dimensional study of the electrical structure of predominantly the upper crust. The data show essentially a resistive uppermost crust, varying from 2 to 6 km in thickness, over a strongly conductive widespread electrical "basement." The general electrical strike of this conductive basement is found to be N30°W, which concurs with the surface geological trend of the region. The data from all profiles were inverted one dimensionally, and from two of the profiles two dimensionally, using different algorithms, to test the accuracy of the one-dimensional images. The main features found are (i) the sediments in the Upper and Middle Belt–Purcell strata are, in general, more conducting than those in the Lower Belt strata of the anticlinorium; (ii) the basement conductor appears to be strongest just to the south of the Canada–United States border, with resistivities of around 1 Ω·m or less; (iii) the western part of the region is more conducting than the eastern part, suggesting that the sources of sedimentation on the two sides of the region were different; (iv) the enhanced conductivity observed can be explained by the presence of mineralization (copper, etc.), rather than other geophysical causes; (v) near the western edge of the Rocky Mountain trench the conductivity increases downwards from near the surface, and near the eastern edge it increases downwards from a depth of about 2 km, suggesting the presence of the asymmetric mineralization in it; (vi) a few kilometres west of the Rocky Mountain trench in the resistive terrain there exist two narrow, vertical, and significantly conductive electrical "conduits"; and (vii) the pervasive conductive basement extends farther east and north than the present location of the copper sulphide mines in northwestern Montana.
Thermal evolution of the southeastern Canadian Cordillera
Authors: Parrish Randall R.
Published: April 2010

The eastern metamorphic culmination of the southern Canadian Cordillera is a composite core complex, which at low structural levels exposes the Monashee décollement, a major contractional fault with large Late Cretaceous to Paleocene east-directed displacement. The hanging wall of this fault, the Selkirk allochthon, is a sheared thrust sheet, recording metamorphic and deformational events spanning the period from ca. 170 to 60 Ma, with younger kinematic and thermal events recorded at progressively deeper levels. The Monashee complex, the footwall terrane of the Monashee décollement, consists of an Early Proterozoic crystalline basement complex overlain by Late Proterozoic and perhaps Phanerozoic metasedimentary rocks. The Monashee complex was significantly metamorphosed and deformed in Paleogene time (60–55 Ma), on the basis of U–Pb data presented in this paper. Analysis of U–Pb titanite data show that the duration of this metamorphic event was but a few million years at most, and it provides a strong argument that the heat source for this metamorphism was the overlying hot Selkirk allochthon. A ~1.85–1.90 Ga metamorphism also is recorded within the Precambrian basement. The tectonometamorphic chronology of the footwall and hanging-wall terranes of the Monashee décollement are very different, and only share Paleogene thermal–tectonic events when the two were structurally juxtaposed by deep-seated thrusting. Although this region is the hinterland of the foreland belt of the southern Cordillera, the thermal and tectonic history of the metamorphic core zone is analogous to that in a thrust belt setting where warmer rocks progressively override cooler rocks as displacement migrates toward the foreland. In such settings, a protracted and more complex thermal history of the hanging wall is juxtaposed with a simpler thermal history of shorter duration of the footwall. Seismic reflection and chronological information indicate that the Monashee décollement is the same structure as the basal décollement beneath the full width of the southern Rocky Mountains, representing its deep-seated continuation in the hinterland. Tectonic denudation resulting from Eocene extension and crustal-scale tilting, followed by late Tertiary erosion, brought these rocks to the surface for study.
Geochemistry of syntectonic, crustal fluid regimes along the Lithoprobe Southern Canadian Cordillera Transect
Authors: Nesbitt Bruce E. , Muehlenbachs Karlis
Published: April 2010

In conjunction with the Lithoprobe southern Canadian Cordillera program, an extensive examination of geochemical indicators of origins, movement, chemical evolution, and economic significance of paleocrustal fluids was conducted. The study area covers approximately 360 000 km2from the Canadian Rockies to Vancouver Island. Research incorporated petrological, mineralogical, fluid-inclusion, δ18O, δD, δ13C, and Rb/Sr studies of samples of quartz ± carbonate veins and other rock types. The results of the study document a variety of pre-, syn-, and postorogenic, crustal fluid events. In the Rockies, a major pre-Laramide hydrothermal event was identified, which was comprised of a west to east migration of warm, saline brines. This was followed by a major circulation of meteoric water in the Rockies during Laramide uplift. In the southern Omineca extensional zone, convecting surface fluids penetrated to the brittle–ductile transition at 350–450 °C and locally into the underlying more ductile rocks. A principal conclusion of the study is that most quartz ± carbonate veins in metamorphic rocks in the southern Canadian Cordillera precipitated from deeply converted surface fluids. This conclusion supports a surface fluid convection model for the genesis of mesothermal Au–quartz veins, common in greenschist-facies rocks worldwide. The combination of our geochemical results with the results of other Lithoprobe studies indicates that widespread and deep convection of surface fluids in rocks undergoing active metamorphism is a commonplace phenomena in extensional settings, while in compressional-thrust settings the depth of penetration of surface fluids is more limited.
Nd–Sr isotopic constraints on the interactions of the Intermontane Superterrane with the western edge of North America in the southern Canadian Cordillera
Authors: Ghosh Dipak K.
Published: April 2010

Sr and Nd isotopic compositions of the late Paleozoic metavolcanics and Late Triassic to early Tertiary granitoids from four magmatic episodes in the southern Canadian Cordillera from the Kootenay Arc to the Fraser Fault have been used to (i) identify the sources of these rocks, (ii) constrain the compressive tectonic history from Middle Jurassic to Paleocene, and (iii) constrain the western boundary of the basement in this region. The 215–190 Ma old primitive granitoids (εNd = +3.1 to 8.7; 87Sr/86Sr = 0.7028 − 0.7043) of the Late Triassic and Early Jurassic magmatic episode were emplaced in the Paleozoic oceanic crust of Quesnellia (εNd = +2.9 to +9.3) prior to its obduction over the basement. In contrast, during the younger magmatic episodes (Middle–Late Jurassic, Cretaceous, and early Tertiary), the granitoids from western Quesnellia show primitive isotopic compositions, and those from eastern Quesnellia show eastward-increasing crust-contaminated compositions. The contaminated characters of the Middle–Late Jurassic (180–150 Ma) granitoids from eastern Quesnellia (εNd = +2.8 to −9.1; 87Sr/86Sr = 0.7041 − 0.7083) suggest that by 180 Ma, the eastern part of Quesnellia obducted over the North American cratonic basement by an amount of about 100 km (Eocene extension corrected) measured from westward shifts of the Nd and Sr isopleths. The eastward-increasing crustal-contamination patterns in the Cretaceous (120–80 Ma) and the Paleocene igneous rocks also show westward shifts of these isopleths by 20 and 70 km, respectively. Thus, we observe that a total 190 km of obduction took place, this amount is similar to the amount of shortening measured in the Rocky Mountains Fold and Thrust Belt, and the western boundary of the North American basement presently lies at least 25–75 km east of the Fraser Fault.
Lithospheric processes and products in the southern Canadian Cordillera: a Lithoprobe perspective
Authors: Cook Frederick A.
Published: April 2010

Analyses of Lithoprobe and other data from southwestern Canada provide new insights on how this portion of the Cordillera formed during plate convergence along the western margin of North America. Crustal rocks are detached from their mantle lithosphere, which must have been consumed during subduction. Detachment occurred at or near the base of the crust beneath the Intermontane and (or) Omineca belts, probably along the tips of tectonic wedges while the rocks were still outboard of the relatively cool, mechanically rigid, North American craton. During the Late Cretaceous and early Tertiary, rotation of detached rocks caught between the North American craton and the oceanic plates accounts for some apparently conflicting results between paleomagnetic data that indicate large northward translation of rocks in the western Cordillera, and regional geological features that appear to preclude comparable amounts of translation of rocks in the eastern Cordillera during the same time interval. Transpression associated with rotation in the Foreland and Omineca belts ceased by the early Tertiary because detached allochthonous rocks of the crust became mechanically attached to, and thus physically part of, North America. Continued plate convergence led to regional transtensional shearing and associated crustal extension in the southern Canadian Cordillera, and perhaps as far inboard as northern Montana, where coeval magmatism was probably associated with new, or reactivation of ancient, lithosphere-penetrating fracture systems.
Medium-sized cyclophanes — Part 85: Benzylation by 8-(bromomethyl)[2.2]metacyclophanes. Through-space electronic interactions of [2.2]metacyclophane benzyl cations
Authors: Shimizu Tomoe , Tanaka Kan , Paudel Arjun , Yamato Takehiko
Published: April 2010

TiCl4-mediated Friedel–Crafts benzylation of benzene with 8-(bromomethyl)[2.2]metacyclophanes to afford 8-benzyl[2.2]metacyclophanes is described. Substituent effect through space on the rate of the benzylation of benzene with a bromomethyl group attached on the opposite aromatic ring was first found in this investigation. Interestingly, the introduction of the substituents at the internal position 16 tends to promote the present benzylation reaction rate 1.8–3.8 times. It was found that the benzyl cation intermediate was stabilized by the the direct through-space cation–π interaction among the opposite benzene ring in the benzylation of [2.2]metacyclophane systems.
Effect of collision energy on cross sections and product alignments for the C(1D) + H2 (v = 0, j = 0) insertion reactions
Authors: Kang Lihua , Dai Bin
Published: April 2010

Quasi-classical trajectory (QCT) calculations of total reaction probabilities and vibrationally state-resolved reaction probabilities at total angular momentum J = 0 as a function of collision energy for the C(1D) + H2 (v = 0, j = 0) reactions have been performed on an ab initio potential-energy surface [ J. Chem. Phys. 2001, 115, 10701]. In addition, the integral cross sections as a function of collision energy have been carried out for the same reaction. The product rotational alignments have also been calculated, which are almost invariant with respect to collision energies.
A novel and efficient cross-coupling of tris(fluorinated phenyl)boroxins with disulfides catalyzed by CuI/1,10-phenanthroline
Authors: Yu Chuanming , Jin Beibei , Liu Zhenyu , Zhong Weihui
Published: April 2010

Under an oxygen atmosphere, the cross-coupling of tris(fluorinated phenyl)boroxins and disulfides catalyzed by CuI/1,10-phenanthroline were smoothly achieved to produce the corresponding asymmetric fluorinated arylsulfides in good-to-excellent yields.
ON GENERATING SOME KNOWN BLACK HOLE SOLUTIONS
Authors: RAHAMAN F. , JAMIL MUBASHER , GHOSH A. , CHAKRABORTY K.
Published: April 2010

In this paper, we have presented an algorithm to generate various black hole solutions in general relativity and alternative theories of gravity. The algorithm involves few dimensional parameters that are assigned suitable values to specify the required black hole.
CASIMIR EFFECT AND FUZZY SPHERE AS EXTRA DIMENSIONAL SPACE
Authors: OIKONOMOU V. K.
Published: April 2010

We calculate the scalar Casimir energy for a Minkowski spacetime with Td × SFZ as extra dimensional space, with Td the d-dimensional commutative torus and SFZ the noncommutative two-sphere. We compute the Casimir energy up to one-loop level in order to address the stabilization of the internal space issue. We found that, contrary to the noncommutative two-torus case, the one-loop Casimir energy is singular, when D = even , therefore cannot give reliable results, when D = 4. However, when D = odd and d = even , the Casimir energy is always regular and a stabilization radius for the internal commutative space exists.
TIME-DEPENDENT EXTRA DIMENSION AND HIGHER-DIMENSIONAL MODIFICATIONS TO THE MATTER CONTENT IN FRW SPACETIMES
Authors: LA CAMERA M.
Published: April 2010

In this work we suggest that higher-dimensional modifications to the matter content in FRW spacetimes can be obtained not only, as first considered by Ponce de Leon, referring to "moving" 4D hypersurfaces non-orthogonal to the time-dependent extra dimension of an embedding 5D manifold, but also referring to "fixed" 4D hypersurfaces orthogonal to a suitable scalar function which defines a static foliation of the 5D manifold and takes the role of the extra dimension in a suitable coordinate system. Results obtained in each approach crucially depend on the method used to identify the 4D metric of our brane universe from the 5D metric of the bulk manifold.
REMOVING THE HAYSTACK — THE CMS TRIGGER AND DATA ACQUISITION SYSTEMS
Authors: O'DELL VIVIAN
Published: April 2010

The CMS Trigger and Data Acquisition Systems have been installed and commissioned and are awaiting data at the Large Hadron Collider. In this article, we describe what factors drove the design and architecture of the systems.
ON NONLINEAR WAVE EQUATIONS WITH BREAKING LOOP-SOLUTIONS
Authors: LI JIBIN , CHEN GUANRONG
Published: April 2010

Using analytic methods from the dynamical systems theory, some new nonlinear wave equations are investigated, which have exact explicit parametric representations of breaking loop-solutions under some fixed parameter conditions. It is shown that these parametric representations are associated with some families of open level-curves of traveling wave systems corresponding to such nonlinear wave equations, each of which lies in an area bounded by a singular straight line and the stable and the unstable manifolds of a saddle point of such a system.
PERIODIC SOLUTIONS FOR SOME NONLINEAR PARTIAL NEUTRAL FUNCTIONAL DIFFERENTIAL EQUATIONS
Authors: BENKHALTI RACHID , ELAZZOUZI ABDELHAI , EZZINBI KHALIL
Published: April 2010

In this work, we study the existence of periodic solutions for some nonlinear partial functional differential equation of neutral type. We assume that the linear part is nondensely defined and satisfies the Hille–Yosida condition. The delayed part is assumed to be ω-periodic with respect to the first argument. Using a fixed point theorem for multivalued mapping, some sufficient conditions are given to prove the existence of periodic solutions.
AMPLITUDE EQUATION FOR STATIONARY CONVECTION IN A VISCOELASTIC MAGNETIC FLUID
Authors: LAROZE D. , MARTINEZ-MARDONES J. , PÉREZ L. M.
Published: April 2010

We report theoretical and numerical results on convection for a magnetic fluid in a viscoelastic carrier liquid. We focus on the stationary convection for idealized boundary conditions. We obtain explicit expressions of convective thresholds in terms of the control parameters of the system. Close to bifurcation, the coefficients of the corresponding amplitude equation are determined analytically. The effect of the rheology and Kelvin force are emphasized and, finally, the nature of the bifurcation is discussed.
CARBON MONOXIDE OXIDATION ON IRIDIUM(111) SURFACES UNDER COLORED NOISE
Authors: CISTERNAS JAIME , ESCAFF DANIEL , DESCALZI ORAZIO , WEHNER STEFAN
Published: April 2010

We study the effect of external noise on the catalytic oxidation of CO on an Iridium(111) single crystal under ultrahigh vacuum conditions. This reaction can be considered as a model of catalysis used in the industry. In the absence of noise, the reaction exhibits one or two stable stationary states, depending on the control parameters such as temperature and partial pressures. When noise is added, for instance, by randomly varying the quality of the influx mixture, the system exhibits stochastic reaction rate and switching. In this work, we present the theoretical predictions for the bistable situation using a number of colored-noise approximations that consider the intensity and correlation of the external fluctuations. As we will show, only some of these approximations are suitable for bistable systems.
QUANTUM-RESONANCE RATCHETS: THEORY AND EXPERIMENT
Authors: DANA I. , ROITBERG V. B. , RAMAREDDY V. , TALUKDAR I. , SUMMY G. S.
Published: April 2010

A theory of quantum ratchets for a particle periodically kicked by a general periodic potential under quantum-resonance conditions is developed for arbitrary values of the conserved quasimomentum β. A special case of this theory is experimentally realized using a Bose–Einstein condensate (BEC) exposed to a pulsed standing light wave. While this case corresponds to completely symmetric potential and initial wave-packet, a purely quantum ratchet effect still arises from the generic noncoincidence of the symmetry centers of these two entities. The experimental results agree well with the theory after taking properly into account the finite quasimomentum width of the BEC. This width causes a suppression of the ratchet acceleration occurring for "resonant" β, so that the mean momentum saturates to a finite ratchet velocity, strongly pronounced relative to that for nonresonant β.
CONTINUOUS-TIME QUANTUM WALKS AND TRAPPING
Authors: AGLIARI ELENA , MÜLKEN OLIVER , BLUMEN ALEXANDER
Published: April 2010

Recent findings suggest that processes such as the excitonic energy transfer through the photosynthetic antenna display quantal features, aspects known from the dynamics of charge carriers along polymer backbones. Hence, in modeling energy transfer one has to leave the classical, master-equation-type formalism and advance towards an increasingly quantum-mechanical picture, while still retaining a local description of the complex network of molecules involved in the transport, say through a tight-binding approach.

Interestingly, the continuous time random walk (CTRW) picture, widely employed in describing transport in random environments, can be mathematically reformulated to yield a quantum-mechanical Hamiltonian of tight-binding type; the procedure uses the mathematical analogies between time-evolution operators in statistical and in quantum mechanics: The result are continuous-time quantum walks (CTQWs). However, beyond these formal analogies, CTRWs and CTQWs display vastly different physical properties. In particular, here we focus on trapping processes on a ring and show, both analytically and numerically, that distinct configurations of traps (ranging from periodical to random) yield strongly different behaviors for the quantal mean survival probability, while classically (under ordered conditions) we always find an exponential decay at long times.
CONSEQUENCES OF THE DYNAMICAL PROPERTIES OF THE SPECIFIC HEAT IN SEMIQUANTUM NONLINEAR HAMILTONIANS
Authors: SARRIS CLAUDIA M. , PROTO ARACELI N.
Published: April 2010

Within the Maximum Entropy Principle context, the specific heat of the system can be expressed in terms of the extensive variables (mean values) or the intensive variables (Lagrange multipliers). It can be shown that the specific heat of the system represented by a given Hamiltonian is not only a thermodynamical quantity but also a dynamical concept. In this contribution, we analyze the consequences emerging from the dynamical properties of the specific heat whose value can be varied using initial conditions independently of the temperature value for the case of semiquantum nonlinear Hamiltonians. An example is outlined.
CHAOS AND STABILITY IN A MODEL OF INHIBITORY NEURONAL NETWORK
Authors: CATSIGERAS ELEONORA
Published: April 2010

We analyze the dynamics of a deterministic model of inhibitory neuronal networks proving that the discontinuities of the Poincaré map produce a never empty chaotic set, while its continuity pieces produce stable orbits. We classify the systems in three types: the almost everywhere (a.e.) chaotic, the a.e. stable, and the combined systems. The a.e. stable are periodic and chaos appears as bifurcations. We prove that a.e. stable systems exhibit limit cycles, attracting a.e. the orbits.
AUDITORY NEURONAL NETWORKS IN SLEEP AND WAKEFULNESS
Authors: VELLUTI RICARDO A. , PEDEMONTE MARISA
Published: April 2010

Auditory system neuronal networks may change on passing from wakefulness to sleep stages, therefore, the sleeping brain can process information in a different fashion that includes networks shifts. The auditory unit phase/locking to hippocampus theta rhythm and the firing shifts on passing to the sleep stages, are the processing representative examples shown. Although still receptive to sensory incoming data, new sets of neuronal networks are reorganized on passing from wakefulness to a different functional state, i.e. sleep.
CLUSTERS IN SOCIAL NETWORKS WITH INCOMPLETE INFORMATION
Authors: CARIDI I. , DORSO C. O. , GALLO P. , SOMIGLIANA C.
Published: April 2010

We have developed a method to recognize communities in networks which lack of some information. It has been conceived to be applied to the problem of getting information about people who were disappeared in the Argentine Province of Tucuman during the period 1975–1983.
QUERYING METABOLISM UNDER DIFFERENT PHYSIOLOGICAL CONSTRAINTS
Authors: CAKMAK ALI , OZSOYOGLU GULTEKIN , HANSON RICHARD W.
Published: April 2010

Metabolism is a representation of the biochemical principles that govern the production, consumption, degradation, and biosynthesis of metabolites in living cells. Organisms respond to changes in their physiological conditions or environmental perturbations (i.e. constraints) via cooperative implementation of such principles. Querying inner working principles of metabolism under different constraints provides invaluable insights for both researchers and educators. In this paper, we propose a metabolism query language (MQL) and discuss its query processing. MQL enables researchers to explore the behavior of the metabolism with a wide-range of predicates including dietary and physiological condition specifications. The query results of MQL are enriched with both textual and visual representations, and its query processing is completely tailored based on the underlying metabolic principles.
CHARACTERIZING THE SPACE OF INTERATOMIC DISTANCE DISTRIBUTION FUNCTIONS CONSISTENT WITH SOLUTION SCATTERING DATA
Authors: KAVATHEKAR PARITOSH A. , CRAIG BRUCE A. , FRIEDMAN ALAN M. , BAILEY-KELLOGG CHRIS , BALKCOM DEVIN J.
Published: April 2010

Scattering of neutrons and X-rays from molecules in solution offers alternative approaches to the study of a wide range of macromolecular structures in their solution state without crystallization. We study one part of the problem of elucidating three-dimensional structure from solution scattering data, determining the distribution of interatomic distances, P(r), where r is the distance between two atoms in the protein molecule. This problem is known to be ill-conditioned: for a single observed diffraction pattern, there may be many consistent distance distribution functions, and there is a risk of overfitting the observed scattering data. We propose a new approach to avoiding this problem: accepting the validity of multiple alternative P(r) curves rather than seeking a single "best."

We place linear constraints to ensure that a computed P(r) is consistent with the experimental data. The constraints enforce smoothness in the P(r) curve, ensure that the P(r) curve is a probability distribution, and allow for experimental error. We use these constraints to precisely describe the space of all consistent P(r) curves as a polytope of histogram values or Fourier coefficients. We develop a linear programming approach to sampling the space of consistent, realistic P(r) curves. On both experimental and simulated scattering data, our approach efficiently generates ensembles of such curves that display substantial diversity.