Meta-igneous granulite and ultramafic xenoliths from basalts of the Midland Valley of Scotland: petrology and mineralogy of the lower crust and upper mantle

ABSTRACTUltramafic xenolith lithologies representative of the mantle beneath the Midland Valley of Scotland comprise magnesian peridotite (predominantly spinel lherzolite) and cumulate wehrlites and clinopyroxenites. The lherzolites are typical of the worldwide type I (Cr-diopside) xenolith suite; their textures and mineral chemistry record a complex thermal and deformational history. The petrographical and mineralogical features of the wehrlite-clinopyroxenite suite can be interpreted within the context of a sequence of cpx + ol ± sp cumulates that have undergone a protracted period of subsoli dus re-equilibration. Mineral compositions are similar to those of type II (Al-augite) ultramafic xenolith suites.Although xenolith populations imply widespread lower crustal heterogeneity, meta-igneous basic granulites form a major component of this region beneath the Midland Valley. They are principally composed of pi + cpx + mt ± opx ± ap; a modal continuum exists from clinopyroxenite to anorthosite, skewed towards plagioclase-rich lithologies. Garnet is rare. Locally, evidence indicates re-equilibration from garnet granulite precursors. Rock densities range from c. 2·8 to c. 3·2 gm . cm−3, implying P-wave velocities in the range 6·5–7·5 km . s−1 consistent with the known seismic properties of the lower crustal layer beneath the Midland Valley. Phase relations are also consistent with equilibration of primary assemblages at depths of 20–35 km. Retrograde reactions indicate that portions of the crust may have had a complex pressure-temperature-time evolution. Major element compositions of the granulites are broadly basaltic, ranging from ne to hy normative with the mean corresponding to alkali olivine basalt. They are distinct, chemically, from basic granulites of the Lewisian complex of NW Scotland.

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The Fairbanks earthquakes of June 21, 1967; aftershock distribution, focal mechanisms, and crustal parameters

Bulletin of the Seismological Society of America ◽

10.1785/bssa0590010073 ◽

1969 ◽

Vol 59 (1) ◽

pp. 73-100

Author(s):

Larry Gedney ◽

Eduard Berg

Keyword(s):

P Wave ◽

Fault System ◽

Crustal Layer ◽

Near Surface ◽

Fault Surface ◽

True Value ◽

Regional Tectonic ◽

Tectonic System ◽

Relationship Of ◽

The Relationship

Abstract A series of moderately severe earthquakes occurred in the vicinity of Fairbanks, Alaska, on the morning of June 21, 1967. During the following months, many thousands of aftershocks were recorded in order to outline the aftershock zone and to resolve the focal mechanism and its relation to the regional tectonic system. No fault is visible at the surface in this area. Foci were found to occupy a relatively small volume in the shape of an ablate cylinder tilted about 30° from the vertical. The center of the zone lay about 12 kilometers southeast of Fairbanks. Focal depths ranged from near-surface to 25 kilometers, although most were in the range 9-16 km. In the course of the investigation, it was found that the Jeffreys and Bullen velocity of 5.56 km/sec for the P wave in the upper crustal layer is very near the true value for this arec, and that the use of 1.69 for the Vp/Vs ratio gives good results in most cases. The proposed faulting mechanism involves nearly equal components of right-lateral strike slip, and normal faulting with northeast side downthrown on a system of sub-parallel faults striking N40°W. The fault surface appears to be curved—dipping from near vertical close to the surface to less steep northeast dips at greater depths. The relationship of this fault system with the grosser aspects of regional tectonism is not clear.

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Abstract 2155: Plasma Adiponectin Levels in Patients with Atrial Fibrillation

Circulation ◽

10.1161/circ.118.suppl_18.s_677-b ◽

2008 ◽

Vol 118 (suppl_18) ◽

Author(s):

Masayuki Shimano ◽

Rei Shibata ◽

Yukiomi Tsuji ◽

Noriyuki Ouchi ◽

Yasuya Inden ◽

...

Keyword(s):

Atrial Fibrillation ◽

Collagen Type ◽

Collagen Type I ◽

High Plasma ◽

P Wave ◽

Atrial Remodeling ◽

Type I ◽

Plasma Adiponectin ◽

Type Iii ◽

And Control

The occurrence and development of atrial fibrillation (AF) are associated with changes in electrical properties and cardiac structure, known as electrical and structural atrial remodeling. AF characterized by atrial remodeling also occurs with obesity-related conditions. Adiponectin, an adipose tissue-derived hormone, exerts beneficial effects on the heart in various pathological conditions. These observations led us to speculate that adiponectin levels affect the development and prevalence of AF. Here, we investigated a potential association between circulating adiponectin levels and atrial remodeling in patients with AF. We measured plasma adiponectin levels, serum carboxy-terminal telopeptide of collagen type I (CITP) levels, as a collagen type I degradation marker, and serum type III procollagen-N-peptide (PIIINP) levels, as a collagen type III synthesis marker in consecutive 414 patients; 225 paroxysmal AF, 81 persistent AF and 108 paroxysmal supra-ventricular tachycardia without AF history (control) patients, who admitted for scheduled radiofrequency catheter ablation. Plasma adiponectin levels were significantly higher in patients with persistent AF compared to paroxysmal AF and control patients (p<0.05). Serum CITP levels, but not serum PIIINP levels, were also higher in patients with persistent AF compared to paroxysmal AF and control patients (p<0.05). In addition, a positive correlation was observed between adiponectin levels and CITP levels (r=0.39, p<0.005) or the P wave duration (r=−0.31, p<0.05) in patients with persistent AF. High plasma adiponectin levels are associated with the presence of persistent AF, which is accompanied by increased CITP levels. Hyperadiponectinemia might also attenuate atrial conduction disturbance. Thus, measurement of plasma adiponectin could be useful for assessment of AF.

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Overview of regional geophysical studies in Manitoba and northwestern Ontario

Canadian Journal of Earth Sciences ◽

10.1139/e82-182 ◽

1982 ◽

Vol 19 (11) ◽

pp. 2049-2059 ◽

Cited By ~ 14

Author(s):

D. H. Hall ◽

W. C. Brisbin

Keyword(s):

Greenstone Belt ◽

Seismic Velocities ◽

Crustal Layer ◽

Northwestern Ontario ◽

Reflection And Refraction ◽

Gravity And Magnetic ◽

Winnipeg River ◽

Lower Crustal ◽

Gravity And Magnetic Anomaly

This paper presents an overview of six geophysical projects (seismic reflection and refraction, gravity and magnetic anomaly interpretation, specific gravity and magnetic property measurements) carried out in an area in Manitoba and northwestern Ontario bounded by 93 and 96°W longitude, and 49 and 51°N latitude.The purpose of the surveys was to define crustal structure in the Kenora–Wabigoon greenstone belt, the Winnipeg River batholithic belt, the Ear Falls – Manigotagan gneiss belt, and the Uchi greenstone belt. The following conclusions emerge.In all of the belts, a major discontinuity divides the crust into the commonly found upper and lower crustal sections. At the top of the lower crust, a seismically distinct layer (the mid-crustal layer) occurs. Seismic velocities in this layer suggest either intermediate to basic igneous rocks or metamorphic rocks of the amphibolite facies.Crustal geophysical characteristics vary sufficiently among the four belts to justify the classification of all four as distinct subprovinces of the Superior Province.Cet article présente une vue générale sur six projets de géophysique (réflexion et réfraction sismique, interprétation d'anomalies de gravité et magnétiques, déterminations de densité et de propriétés magnétiques) réalisés dans une région du Manitoba et du nord-ouest de l'Ontario encadrée par les longitudes 93 et 96°O et les latitudes 49 et 51°N.

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Constraints on the composition of the crust and uppermost mantle in northwestern Canada: Vp/Vs variations along Lithoprobe's SNorCLE transect

Canadian Journal of Earth Sciences ◽

10.1139/e05-028 ◽

2005 ◽

Vol 42 (6) ◽

pp. 1205-1222 ◽

Cited By ~ 34

Author(s):

Gabriela Fernández-Viejo ◽

Ron M Clowes ◽

J Kim Welford

Keyword(s):

Wave Velocity ◽

Upper Mantle ◽

Laboratory Data ◽

High Ratio ◽

P Wave ◽

S Wave ◽

Uppermost Mantle ◽

Crust And Upper Mantle ◽

Slave Craton ◽

Crustal Composition

Shear-wave seismic data recorded along four profiles during the SNoRE 97 (1997 Slave Northern Cordillera Refraction Experiment) refraction wide-angle reflection experiment in northwestern Canada are analyzed to provide S-wave velocity (Vs) models. These are combined with previous P-wave velocity (Vp) models to produce cross sections of the ratio Vp/Vs for the crust and upper mantle. The Vp/Vs values are related to rock types through comparisons with published laboratory data. The Slave craton has low Vp/Vs values of 1.681.72, indicating a predominantly silicic crustal composition. Higher values (1.78) for the Great Bear and eastern Hottah domains of the Wopmay orogen imply a more mafic than average crustal composition. In the western Hottah and Fort Simpson arc, values of Vp/Vs drop to ∼1.69. These low values continue westward for 700 km into the Foreland and Omineca belts of the Cordillera, providing support for the interpretation from coincident seismic reflection studies that much of the crust from east of the Cordilleran deformation front to the Stikinia terrane of the Intermontane Belt consists of quartzose metasedimentary rocks. Stikinia shows values of 1.781.73, consistent with its derivation as a volcanic arc terrane. Upper mantle velocity and ratio values beneath the Slave craton indicate an ultramafic peridotitic composition. In the Wopmay orogen, the presence of low Vp/Vs ratios beneath the Hottah Fort Simpson transition indicates the presence of pyroxenite in the upper mantle. Across the northern Cordillera, low Vp values and a moderate-to-high ratio in the uppermost mantle are consistent with the region's high heat flow and the possible presence of partial melt.

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Crustal velocity structure of the Apennines (Italy) from P-wave travel time tomography

Annals of Geophysics ◽

10.4401/ag-4042 ◽

1996 ◽

Vol 39 (6) ◽

Author(s):

C. Chiarabba ◽

A. Amato

Keyword(s):

Velocity Structure ◽

P Wave ◽

Depth Interval ◽

Low Velocity ◽

Data Set ◽

Arrival Times ◽

Velocity Anomaly ◽

Minimum Number ◽

Velocity Images ◽

Lower Crustal

In this paper we provide P-wave velocity images of the crust underneath the Apennines (Italy), focusing on the lower crustal structure and the Moho topography. We inverted P-wave arrival times of earthquakes which occurred from 1986 to 1993 within the Apenninic area. To overcome inversion instabilities due to noisy data (we used bulletin data) we decided to resolve a minimum number of velocity parameters, inverting for only two layers in the crust and one in the uppermost mantle underneath the Moho. A partial inversion of only 55% of the overall dataset yields velocity images similar to those obtained with the whole data set, indicating that the depicted tomograms are stable and fairly insensitive to the number of data used. We find a low-velocity anomaly in the lower crust extending underneath the whole Apenninic belt. This feature is segmented by a relative high-velocity zone in correspondence with the Ortona-Roccamonfina line, that separates the northern from the southern Apenninic arcs. The Moho has a variable depth in the study area, and is deeper (more than 37 km) in the Adriatic side of the Northern Apennines with respect to the Tyrrhenian side, where it is found in the depth interval 22-34 km.

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Crustal velocity structure from SAREX, the Southern Alberta Refraction Experiment

Canadian Journal of Earth Sciences ◽

10.1139/e01-070 ◽

2002 ◽

Vol 39 (3) ◽

pp. 351-373 ◽

Cited By ~ 39

Author(s):

Ron M Clowes ◽

Michael JA Burianyk ◽

Andrew R Gorman ◽

Ernest R Kanasewich

Keyword(s):

Velocity Structure ◽

Data Interpretation ◽

Crustal Thickening ◽

Tectonic Zone ◽

Crustal Layer ◽

Crustal Velocity ◽

Crustal Velocity Structure ◽

Southern Alberta ◽

Magmatic Underplating ◽

Lower Crustal

Lithoprobe's Southern Alberta Refraction Experiment, SAREX, extends 800 km from east-central Alberta to central Montana. It was designed to investigate crustal velocity structure of the Archean domains underlying the Western Canada Sedimentary Basin. From north to south, SAREX crosses the Loverna domain of the Hearne Province, the Vulcan structure, the Medicine Hat block (previously considered part of the Hearne Province), the Great Falls tectonic zone, and the northern Wyoming Province. Ten shot points along the profile in Canada were recorded on 521 seismographs deployed at 1 km intervals. To extend the line, an additional 140 seismographs were deployed at intervals of 1.252.50 km in Montana. Data interpretation used an iterative application of damped least-squares inversion of traveltime picks and forward modeling. Results show different velocity structures for the major blocks (Loverna, Medicine Hat, and Wyoming), indicating that each is distinct. Wavy undulations in the velocity structure of the Loverna block may be associated with internal crustal deformation. The most prominent feature of the model is a thick (1025 km) lower crustal layer with high velocities (7.57.9 km/s) underlying the Medicine Hat and Wyoming blocks. Based on data from lower crustal xenoliths in the region, this layer is interpreted to be the result of Paleoproterozoic magmatic underplating. Crustal thickness varies from 40 km in the north to almost 60 km in the south, where the high-velocity layer is thickest. Uppermost mantle velocities range from 8.05 to 8.2 km/s, with the higher values below the thicker crust. Results from SAREX and other recent studies are synthesized to develop a schematic representation of Archean to Paleoproterozoic tectonic development for the region encompassing the profile. Tectonic processes associated with this development include collisions of continental blocks, subduction, crustal thickening, and magmatic underplating.

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The Australian Plate and underlying mantle from waveform tomography with massive datasets

10.5194/egusphere-egu21-5272 ◽

2021 ◽

Author(s):

Janneke de Laat ◽

Sergei Lebedev ◽

Bruna Chagas de Melo ◽

Nicolas Celli ◽

Raffaele Bonadio

Keyword(s):

Structural Information ◽

Azimuthal Anisotropy ◽

P Wave ◽

Depth Range ◽

S Wave ◽

Crust And Upper Mantle ◽

Southern Boundary ◽

Velocity Anomaly ◽

Australian Plate ◽

Australian Continent

We present a new S-wave velocity tomographic model of the Australian Plate, Aus21.&#160; It is constrained by waveforms of 0.9 million seismograms with both the corresponding sources and stations located within the half-hemisphere centred at the Australian continent. Waveform inversion extracts structural information from surface, S- and multiple S-waves on the seismograms in the form of a set of linear equations. These equations are then combined in a large linear system and inverted jointly to obtain a tomographic model of S- and P-wave speeds and S-wave azimuthal anisotropy of the crust and upper mantle. The model has been validated by resolution tests and, for particular locations in Australia with notable differences with previous models, by independent inter-station measurements of surface-wave phase velocities, which we performed using available array data.&#160;&#160;Aus21 offers new insights into the structure and evolution of the Australian Plate and its boundaries. The Australian cratonic lithosphere occupies nearly all of the western and central Australia but shows substantial lateral heterogeneity. It extends up to the northern edge of the plate, where it is colliding with island arcs, without subducting. The rugged eastern boundary of the cratonic lithosphere provides a lithospheric definition of the Tasman Line. The thin, warm lithosphere below the eastern part of the continent, east of the Tasman Line, underlies the Cenozoic volcanism locations in the area. The lithosphere is also thin and warm below much of the Tasman Sea, underlying the Lord Howe hotspot and the submerged part of western Zealandia. A low velocity anomaly that may indicate the single source of the Lord Howe and Tasmanid hotspots is observed in the transition zone offshore the Australian continent, possibly also sourcing the East Australia hotspot. Another potential hotspot source is identified below the Kermadec Trench, causing an apparent slab gap in the overlying slab and possibly related to the Samoa Hotspot to the north. Below a portion of the South East Indian Ridge (the southern boundary of the Australian Plate) a pronounced high velocity anomaly is present in the 200-400 km depth range just east of the Australian-Antarctic Discordance (AAD), probably linked to the evolution of this chaotic ridge system.

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Three-Dimensional Imaging of the Crust and Upper Mantle in the Long Valley-Mono Craters Region, California, Using Teleseismic P-Wave Residuals

IAVCEI Proceedings in Volcanology - Volcanic Seismology ◽

10.1007/978-3-642-77008-1_23 ◽

1992 ◽

pp. 339-358 ◽

Cited By ~ 2

Author(s):

P. B. Dawson ◽

H. M. Iyer ◽

J. R. Evans

Keyword(s):

Upper Mantle ◽

Three Dimensional ◽

P Wave ◽

Crust And Upper Mantle ◽

Three Dimensional Imaging ◽

Mono Craters ◽

Long Valley

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The CIELO Seismic Experiment

Seismological Research Letters ◽

10.1785/0220210237 ◽

2021 ◽

Author(s):

Heather A. Ford ◽

Maximiliano J. Bezada ◽

Joseph S. Byrnes ◽

Andrew Birkey ◽

Zhao Zhu

Keyword(s):

Receiver Function ◽

Function Analysis ◽

P Wave ◽

Crust And Upper Mantle ◽

Waveform Data ◽

Wyoming Craton ◽

Sensor Orientation ◽

Seismic Experiment ◽

Short Period ◽

Receiver Function Analysis

Abstract The Crust and lithosphere Investigation of the Easternmost expression of the Laramide Orogeny was a two-year deployment of 24 broadband, compact posthole seismometers in a linear array across the eastern half of the Wyoming craton. The experiment was designed to image the crust and upper mantle of the region to better understand the evolution of the cratonic lithosphere. In this article, we describe the motivation and objectives of the experiment; summarize the station design and installation; provide a detailed accounting of data completeness and quality, including issues related to sensor orientation and ambient noise; and show examples of collected waveform data from a local earthquake, a local mine blast, and a teleseismic event. We observe a range of seasonal variations in the long-period noise on the horizontal components (15–20 dB) at some stations that likely reflect the range of soil types across the experiment. In addition, coal mining in the Powder River basin creates high levels of short-period noise at some stations. Preliminary results from Ps receiver function analysis, shear-wave splitting analysis, and averaged P-wave delay times are also included in this report, as is a brief description of education and outreach activities completed during the experiment.

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