scholarly journals High 3He/4He in central Panama reveals a distal connection to the Galápagos plume

2021 ◽  
Vol 118 (47) ◽  
pp. e2110997118
Author(s):  
David V. Bekaert ◽  
Esteban Gazel ◽  
Stephen Turner ◽  
Mark D. Behn ◽  
J. Marten de Moor ◽  
...  
Keyword(s):  
Mantle Flow ◽  
Transport Mechanisms ◽  
Lithosphere Thinning ◽  
Enriched Mantle ◽  
Deep Interior ◽  
Southern Central ◽  
Galapagos Plume ◽  
Central Panama ◽  
Slab Window ◽  
Lava Geochemistry

It is well established that mantle plumes are the main conduits for upwelling geochemically enriched material from Earth's deep interior. The fashion and extent to which lateral flow processes at shallow depths may disperse enriched mantle material far (>1,000 km) from vertical plume conduits, however, remain poorly constrained. Here, we report He and C isotope data from 65 hydrothermal fluids from the southern Central America Margin (CAM) which reveal strikingly high 3He/4He (up to 8.9RA) in low-temperature (≤50 °C) geothermal springs of central Panama that are not associated with active volcanism. Following radiogenic correction, these data imply a mantle source 3He/4He >10.3RA (and potentially up to 26RA, similar to Galápagos hotspot lavas) markedly greater than the upper mantle range (8 ± 1RA). Lava geochemistry (Pb isotopes, Nb/U, and Ce/Pb) and geophysical constraints show that high 3He/4He values in central Panama are likely derived from the infiltration of a Galápagos plume–like mantle through a slab window that opened ∼8 Mya. Two potential transport mechanisms can explain the connection between the Galápagos plume and the slab window: 1) sublithospheric transport of Galápagos plume material channeled by lithosphere thinning along the Panama Fracture Zone or 2) active upwelling of Galápagos plume material blown by a “mantle wind” toward the CAM. We present a model of global mantle flow that supports the second mechanism, whereby most of the eastward transport of Galápagos plume material occurs in the shallow asthenosphere. These findings underscore the potential for lateral mantle flow to transport mantle geochemical heterogeneities thousands of kilometers away from plume conduits.

Chemical boundary layers of the mantle and core

1989 ◽  
Vol 328 (1599) ◽  
pp. 441-442 ◽  
Keyword(s):  
Boundary Layer ◽  
Heat Flow ◽  
Large Scale ◽  
High Heat ◽  
Mantle Flow ◽  
Sufficient Information ◽  
Deep Interior ◽  
Gravimetric Data ◽  
Flow Through ◽  
The Stability

There is now sufficient information from seismological mapping of the Earth’s deep interior to draw some preliminary conclusions regarding nature of large-scale mantle flow. This paper examines three features of mantle heterogeneity. Seismological studies confirm the existence of a thick (more than 300 km) thermal boundary layer (tbl) beneath the ancient cratonic nuclei. Petrological and gravimetric data imply that the continental tbl is stabilized against convective disruption by a buoyant, viscous, chemical boundary layer (cbl) depleted in Fe and A1 relative to Mg. Geothermal constraints require high heat production within the cbl and low heat flow through its base, indicating that the cbl has been recharged by large-ion lithophile (lil) elements after primary depletion events. Formation of this continental tectosphere cannot be simple conductive cooling, as in the oceans, but must involve several stages characterized by different timescales, terminating with crustal stabilization; the advective thickening of a basalt-depleted, LiL-rich cbl in episodes of compressive orogenesis (e.g. supercontinent assembly) may be an important mechanism for tectospheric consolidation. The stability and low basal heat flow of the cratonic cbl are evidence that the positions of the continents through time are coupled to the upward flow of material from the deep mantle.

scholarly journals Chemical trends in ocean islands explained by plume–slab interaction

2018 ◽  
Vol 115 (17) ◽  
pp. 4351-4356 ◽  
Author(s):  
Juliane Dannberg ◽  
Rene Gassmöller
Keyword(s):  
Lower Mantle ◽  
Computational Models ◽  
Oceanic Islands ◽  
Mantle Flow ◽  
Exact Nature ◽  
Key Factors ◽  
Chemical Zoning ◽  
Chemical Gradients ◽  
Deep Interior ◽  
Lowermost Mantle

Earth’s surface shows many features, of which the genesis can be understood only through their connection with processes in Earth’s deep interior. Recent studies indicate that spatial geochemical patterns at oceanic islands correspond to structures in the lowermost mantle inferred from seismic tomographic models. This suggests that hot, buoyant upwellings can carry chemical heterogeneities from the deep lower mantle toward the surface, providing a window to the composition of the lowermost mantle. The exact nature of this link between surface and deep Earth remains debated and poorly understood. Using computational models, we show that subducted slabs interacting with dense thermochemical piles can trigger the ascent of hot plumes that inherit chemical gradients present in the lowermost mantle. We identify two key factors controlling this process: (i) If slabs induce strong lower-mantle flow toward the edges of these piles where plumes rise, the pile-facing side of the plume preferentially samples material originating from the pile, and bilaterally asymmetric chemical zoning develops. (ii) The composition of the melt produced reflects this bilateral zoning if the overlying plate moves roughly perpendicular to the chemical gradient in the plume conduit. Our results explain some of the observed geochemical trends of oceanic islands and provide insights into how these trends may originate.

scholarly journals Progressive weakening within the overriding plate during dual inward dipping subduction

2022 ◽  
Author(s):  
ZHIBIN LEI ◽  
J. Davies
Keyword(s):  
Strain Rate ◽  
Dominant Role ◽  
Viscosity Reduction ◽  
Mantle Flow ◽  
Complex Deformation ◽  
Geodynamic Process ◽  
Multiple Parameters ◽  
Lithosphere Thinning ◽  
Subducting Plate ◽  
Deformation Patterns

Dual inward dipping subduction often produces complex deformation patterns in the overriding plate. However, the geodynamic process of how dual inward dipping subduction relates to this deformation is still poorly understood. Here we apply a composite viscosity, dependent on multiple parameters, e.g., temperature, pressure, strain rate etc., in 2-D thermo-mechanical numerical modelling to investigate how dual inward dipping subduction modifies the rheological structure of the overriding plate. Three variables are investigated to understand what controls the maximum degree of weakening. We find that the initial length and thickness of the overriding plate are negatively correlated with the magnitude of viscosity reduction. While the initial thickness of the subducting plate positively relates to the magnitude of viscosity reduction. The progressive weakening can result in a variety of stretching states ranging from 1) little or no lithosphere thinning and extension, to 2) limited thermal lithosphere thinning, and 3) localised rifting followed by spreading extension. Compared with single sided subduction, dual inward dipping subduction further reduces the magnitude of viscosity of the overriding plate. It does this by creating a dynamic fixed boundary condition for the overriding plate and forming a stronger upwelling mantle flow underlying the overriding plate. Three types of feedback weakening cycles are recognised, among which the strain rate weakening mechanism plays the dominant role in lowering the viscosity of the overriding plate throughout the simulation. Strain rate weakening is also a precondition for initiating thermal weakening, strain localisation and lithosphere thinning.

Toroidal mantle flow through the western U.S. slab window

Geology ◽  
2008 ◽  
Vol 36 (4) ◽  
pp. 295 ◽  
Author(s):  
G. Zandt ◽  
E. Humphreys
Keyword(s):  
Mantle Flow ◽  
Flow Through ◽  
Slab Window

Mantle flow through the Northern Cordilleran slab window revealed by volcanic geochemistry

Geology ◽  
2011 ◽  
Vol 39 (3) ◽  
pp. 267-270 ◽  
Author(s):  
Derek J. Thorkelson ◽  
Julianne K. Madsen ◽  
Christa L. Sluggett
Keyword(s):  
Mantle Flow ◽  
Flow Through ◽  
Slab Window

Seismic Tomography of Kamchatkan Volcanoes

2021 ◽  
Author(s):  
I.Yu. Koulakov
Keyword(s):  
Seismic Tomography ◽  
Regional Scale ◽  
Active Regions ◽  
Recent Decade ◽  
Kamchatka Peninsula ◽  
Integral Model ◽  
Mantle Flow ◽  
Local Networks ◽  
The World ◽  
Slab Window

Abstract —The Kamchatka Peninsula is one of the most tectonically active regions in the world, where intensive and diverse modern volcanic activity takes place. In the recent decade, substantial progress in the investigation of deep structures beneath Kamchatka has been achieved owing to numerous tomography studies based on seismological data provided by permanent stations and temporary networks deployed in some key areas. The goal of this review is summarizing and systematizing dozens of separate multiscale geophysical studies in Kamchatka and constructing an integral model of volcano-feeding systems. An important part of this review contains the description of results of various seismic studies related to the Klyuchevskoy group volcanoes, which can now be considered one of the best studied volcanic areas in the world. The results of the regional-scale seismic tomography reveal the existence of the Pacific slab window, which determines the particular activity of the Klyuchevskoy group volcanoes. Middle-scale tomography studies have found traces of an ascending hot mantle flow that passes through the slab window, reaches the bottom of the crust below Shiveluch Volcano, and then propagates laterally toward the Klyuchevskoy group. Seismic models of the entire crust in the area of the Klyuchevskoy group were used to identify different mechanisms of magmatic feeding of three most active volcanoes: Klyuchevskoy, Bezymianny, and Tolbachik. The data of local networks deployed on several volcanoes of Kamchatka were used to image the magma sources in the upper crust, which are directly responsible for the current eruption activity. The comparison of the results for the Kamchatka volcanoes with tomography models of several other volcanoes of the world allowed determining some common features and differences in feeding active magmatic systems.

Mantle flow and dynamic topography associated with slab window opening: Insights from laboratory models

2010 ◽  
Vol 496 (1-4) ◽  
pp. 83-98 ◽  
Author(s):  
Benjamin Guillaume ◽  
Monica Moroni ◽  
Francesca Funiciello ◽  
Joseph Martinod ◽  
Claudio Faccenna
Keyword(s):  
Mantle Flow ◽  
Dynamic Topography ◽  
Window Opening ◽  
Laboratory Models ◽  
Slab Window

Physical Properties of Isolated Perfused Renal Tubular Basement Membranes

1971 ◽  
Vol 29 ◽  
pp. 390-391
Author(s):  
Jared Grantham ◽  
Larry Welling
Keyword(s):  
Basement Membrane ◽  
Basement Membranes ◽  
Transport Mechanisms ◽  
Permeability Characteristics ◽  
Peritubular Capillaries ◽  
Strategic Location ◽  
Tubular Lumen ◽  
Glomerular Filtrate ◽  
Urine Formation ◽  
Renal Tubular

In the course of urine formation in mammalian kidneys over 90% of the glomerular filtrate moves from the tubular lumen into the peritubular capillaries by both active and passive transport mechanisms. In all of the morphologically distinct segments of the renal tubule, e.g. proximal tubule, loop of Henle and distal nephron, the tubular absorbate passes through a basement membrane which rests against the basilar surface of the epithelial cells. The basement membrane is in a strategic location to affect the geometry of the tubules and to influence the movement of tubular absorbate into the renal interstitium. In the present studies we have determined directly some of the mechanical and permeability characteristics of tubular basement membranes.

Alveolobronchiolar transport mechanisms

1973 ◽  
Vol 131 (1) ◽  
pp. 109-114 ◽  
Author(s):  
G. M. Green
Keyword(s):  
Transport Mechanisms
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