scholarly journals Strength contrast between plagioclase and olivine at water-rich Moho depths

2010 ◽  
Vol 105 (5) ◽  
pp. 286-290
Author(s):  
Shintaro AZUMA ◽  
Ikuo KATAYAMA ◽  
Ken-ichi HIRAUCHI ◽  
Shigeru YAMASHITA
Keyword(s):  
Moho Depths

Xác định mặt Moho ở Miền Nam Việt Nam

2008 ◽  
Vol 30 (4) ◽  
pp. 403-409
Author(s):  
Đỗ Đăng Trình ◽  
Bùi Thị Ánh Phương ◽  
Đặng Văn Liệt
Keyword(s):  
Viet Nam ◽  
The South ◽  
Moho Depths

Moho depths in the south of Vietnam

The preserved plume conduits of the Caribbean Large Igneous Plateau and their relation with the Galápagos hotspot back to 90 Ma

2021 ◽  
Author(s):  
Angela Maria Gomez Garcia ◽  
Eline Le Breton ◽  
Magdalena Scheck-Wenderoth ◽  
Gaspar Monsalve ◽  
Denis Anikiev
Keyword(s):  
Reference Frames ◽  
Thermal Anomaly ◽  
Caribbean Region ◽  
Positive Density ◽  
South American ◽  
Kinematic Models ◽  
Tomographic Data ◽  
The Caribbean ◽  
Moho Depths ◽  
South American Continent

<p>Remnants of the Caribbean Large Igneous Plateau (C-LIP) are found as thickened zones of oceanic crust in the Caribbean Sea, that formed during strong pulses of magmatic activity around 90 Ma. Previous studies have proposed the Galápagos hotspot as the origin of the thermal anomaly responsible for the development of this igneous province. Particularly, geochemical signature relates accreted C-LIP fragments along northern South America with the well-known hotspot material.</p><p>In this research, we use 3D lithospheric-scale structural and density models of the Caribbean region, in which up-to-date geophysical datasets (i.e.: tomographic data, Moho depths, sedimentary thickness, and bathymetry) have been integrated. Based on the gravity residuals (modelled minus observed EIGEN6C-4 dataset), we reconstruct density heterogeneities both in the crust and the uppermost oceanic mantle (< 50km).</p><p>Our results suggest the presence of two positive mantle density anomalies in the Colombian and the Venezuelan basins, interpreted as the preserved plume material which migrated together with the Proto-Caribbean plate from the east Pacific. Such bodies have never been identified before, but a positive density trend is also observed in the mantle tomography, at least down to 75 km depth.</p><p>Using recently published regional plate kinematic models and absolute reference frames, we test the hypothesis of the C-LIP origin in the Galápagos hotspot. However, misfits of up to ~3000 km between the present hotspot location and the mantle anomalies, reconstructed back to 90 Ma, is observed, as other authors reported in the past.</p><p>Therefore, we discuss possible sources of error responsible for this offset and pose two possible interpretations: 1. The Galápagos hotspot migrated (~1200-3000 km) westward while the Proto-Caribbean moved to the northeast, or 2. The C-LIP was formed by a different plume, which – if considered fixed - would be nowadays located below the South American continent.</p>

scholarly journals Geodynamic and structural factors of porphyritic objects localization in Sikhote-Alin

2018 ◽  
Vol 56 ◽  
pp. 04020
Author(s):  
Viktor Nevstruyev ◽  
Olga Kozlova
Keyword(s):  
Porphyry Copper ◽  
Volcanic Belt ◽  
Structural Factors ◽  
Sikhote Alin ◽  
The Andes ◽  
Tectonic Disturbances ◽  
Pacific Slab ◽  
Moho Depths ◽  
Objects Localization

Ore bearing porphyritic systems of Sikhote-Alin form linear zones in Cretaceous volcanic belt. They are limited to zones of tectonic disturbances at Moho depths of 19-25 mi (30-40 km). Pacific slab lies at around 340 miles (548 km) below the volcanic belt, which matches the slab depth of porphyritic deposits formation belts in the Andes and Indonesia-Tonga region. Formation of porphyry copper systems is linked to the processes of metalliferous fluids intrusion at slab destruction areas near asthenosphere.

Concluding remarks

1987 ◽  
Vol 321 (1557) ◽  
pp. 275-276 ◽  
Keyword(s):  
Regional Metamorphism ◽  
Physical Conditions ◽  
New Period ◽  
Strongly Connected ◽  
History Of ◽  
Critical Problems ◽  
Stable Continental Regions ◽  
Actual Plate ◽  
Moho Depths ◽  
Metamorphic Terranes

The focus of this discussion meeting is strongly connected to that of the history of continental crust. I was reminded of G. K. Gilbert (1893), who said that 'the permanence of the continental plateau, though highly probable, is not yet fully established; and the doctrine of continental growth, though generally accepted, has not been placed beyond the field of profitable discussion’. Recently, Kerr (1985) remarked that we increasingly see continents as a ‘collage of wandering fragments’, and this present discussion has been most concerned with processes associated with this model. I think we are sometimes confused by what is formed, when we observe what is preserved. Continental metamorphism presents us with a great puzzle. Given the present heat flow, stable continental regions have temperatures little above 400 °C at Moho depths; the continents should be dominated by facies of the lowest grades. Yet continental rocks show an amazing diversity of P—T regimes, far exceeding any normal range. Verhoogen (1980) wrote ‘as deformation and orogeny are commonly associated with regional metamorphism, orogeny should perhaps be described as a thermal disturbance, rather than a mechanical one’. Modern metamorphic studies involve the central theme of tracking the convective style of the earth through time. We are now entering a new period of observation, where deep continental structure is being refined by seismic and electrical methods, while actual plate motions can be observed by satellites. Many of the metamorphic terranes discussed at this meeting involve subduction and collision-related phenomena. Recent studies of the subduction process (Uyeda 1983; Yorath et al. 1985; Kaiko Staff 1985) are beginning to elucidate the critical problems of the mechanics of subduction and the materials involved (even serpentine and diamonds; see, for example, Schulz 1986; Ozima et al. 1985). Such studies feed back to the complex paths now being revealed by the metamorphic record. Rocks show us the range of physical conditions, and place some constraints on time, while modern geophysics can show the mechanisms. We are reaching the point where petrology and geophysics are joining to produce sound models of dynamics and thermal history.

Moho Variations across the Northern Canadian Cordillera

2020 ◽  
Vol 91 (6) ◽  
pp. 3076-3085 ◽  
Author(s):  
Pascal Audet ◽  
Derek L. Schutt ◽  
Andrew J. Schaeffer ◽  
Clément Estève ◽  
Richard C. Aster ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
High Elevation ◽  
Receiver Functions ◽  
Moho Depth ◽  
Canadian Cordillera ◽  
Regional Seismicity ◽  
Thermal Buoyancy ◽  
Mackenzie Mountains ◽  
Moho Depths ◽  
Array Density

Abstract Moho morphology in orogens provides important constraints on the rheology and density structure of the crust and underlying mantle. Previous studies of Moho geometry in the northern Canadian Cordillera (NCC) using very sparse seismic data have indicated a flat and shallow (∼30–35  km) Moho, despite an average elevation of >1000  m above sea level attributable to increased thermal buoyancy and lower crustal flow due to elevated temperatures. We estimate Moho depth using receiver functions from an expanded dataset incorporating 173 past and recently deployed broadband seismic stations, including the EarthScope Transportable Array, Mackenzie Mountains transect, and other recent deployments. We determine Moho depths in the range 27–43 km, with mean and standard deviations of 33.0 and 3.0 km, respectively, and note thickened crust beneath high-elevation seismogenic regions. In the Mackenzie Mountains, thicker crust is interpreted as due to crustal stacking from thrust sheet emplacement. The edge of this region of thickened crust is interpreted to delineate the extent of the former Laurentian margin beneath the NCC and is associated with a transition from thrust to strike-slip faulting observed in regional seismicity. More geographically extensive seismograph deployments at EarthScope Transportable Array density and scale will be required to further extend crustal-scale and lithosphere-scale imaging in western Canada.

IMPLEMENTING SEISMIC MOHO DEPTHS IN GEOID COMPUTATION

Survey Review ◽  
2003 ◽  
Vol 37 (289) ◽  
pp. 235-245 ◽  
Author(s):  
Hussein Abd-Elmotaal
Keyword(s):  
Moho Depths ◽  
Geoid Computation

scholarly journals On Moho Determination by the Vening Meinesz-Moritz Technique

2021 ◽  
Author(s):  
Lars Erik Sjöberg ◽  
Majid Abrehdary
Keyword(s):  
Least Squares ◽  
Moho Depth ◽  
Glacial Isostatic Adjustment ◽  
Altimetry Data ◽  
Satellite Gravity ◽  
Isostatic Adjustment ◽  
Uncertainty Estimates ◽  
Least Squares Adjustment ◽  
Moho Depths ◽  
Vening Meinesz

This chapter describes a theory and application of satellite gravity and altimetry data for determining Moho constituents (i.e. Moho depth and density contrast) with support from a seismic Moho model in a least-squares adjustment. It presents and applies the Vening Meinesz-Moritz gravimetric-isostatic model in recovering the global Moho features. Internal and external uncertainty estimates are also determined. Special emphasis is devoted to presenting methods for eliminating the so-called non-isostatic effects, i.e. the gravimetric signals from the Earth both below the crust and from partly unknown density variations in the crust and effects due to delayed Glacial Isostatic Adjustment as well as for capturing Moho features not related with isostatic balance. The global means of the computed Moho depths and density contrasts are 23.8±0.05 km and 340.5 ± 0.37 kg/m3, respectively. The two Moho features vary between 7.6 and 70.3 km as well as between 21.0 and 650.0 kg/m3. Validation checks were performed for our modeled crustal depths using a recently published seismic model, yielding an RMS difference of 4 km.

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