The zone of influence of the subducting slab in the asthenospheric mantle

Abstract Late Mesozoic igneous rocks are important for deciphering the Mesozoic tectonic setting of NE China. In this paper, we present whole-rock geochemical data, zircon U–Pb ages and Lu–Hf isotope data for Early Cretaceous volcanic rocks from the Tulihe area of the northern Great Xing’an Range (GXR), with the aim of evaluating the petrogenesis and genetic relationships of these rocks, inferring crust–mantle interactions and better constraining extension-related geodynamic processes in the GXR. Zircon U–Pb ages indicate that the rhyolites and trachytic volcanic rocks formed during late Early Cretaceous time (c. 130–126 Ma). Geochemically, the highly fractionated I-type rhyolites exhibit high-K calc-alkaline, metaluminous to weakly peraluminous characteristics. They are enriched in light rare earth elements (LREEs) and large-ion lithophile elements (LILEs) but depleted in high-field-strength elements (HFSEs), with their magmatic zircons ϵHf(t) values ranging from +4.1 to +9.0. These features suggest that the rhyolites were derived from the partial melting of a dominantly juvenile, K-rich basaltic lower crust. The trachytic volcanic rocks are high-K calc-alkaline series and exhibit metaluminous characteristics. They have a wide range of zircon ϵHf(t) values (−17.8 to +12.9), indicating that these trachytic volcanic rocks originated from a dominantly lithospheric-mantle source with the involvement of asthenospheric mantle materials, and subsequently underwent extensive assimilation and fractional crystallization processes. Combining our results and the spatiotemporal migration of the late Early Cretaceous magmatic events, we propose that intense Early Cretaceous crust–mantle interaction took place within the northern GXR, and possibly the whole of NE China, and that it was related to the upwelling of asthenospheric mantle induced by rollback of the Palaeo-Pacific flat-subducting slab.

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Phanerozoic record of mantle-dominated arc magmatic surges in the Zealandia Cordillera

Geology ◽

10.1130/g48916.1 ◽

2021 ◽

Author(s):

M.F. Ringwood ◽

J.J. Schwartz ◽

R.E. Turnbull ◽

A.J. Tulloch

Keyword(s):

Detrital Zircon ◽

Mantle Melting ◽

Dynamic Changes ◽

Plate Deformation ◽

Asthenospheric Mantle ◽

Addition Rate ◽

Pacific Margin ◽

Cyclical Process ◽

Tectonic Settings ◽

Subducting Slab

We integrated new and existing bedrock and detrital zircon dates from the Zealandia Cordillera to explore the tempo of Phanerozoic arc magmatism along the paleo-Pacific margin of southeast Gondwana. We found that episodic magmatism was dominated by two high-magma-addition-rate (MAR) events spaced ~250 m.y. apart in the Devonian (370–368 Ma) and the Early Cretaceous (129–105 Ma). The intervening interval between high-MAR events was characterized by prolonged, low-MAR activity in a geographically stable location for more than 100 m.y. We found that the two high-MAR events in Zealandia have distinct chemistries (S-type for the Devonian and I-type for the Cretaceous) and are unlikely to have been related by a repeating, cyclical process. Like other well-studied arc systems worldwide, the Zealandia Cordillera high-MAR events were associated with upper-plate deformation; however, the magmatic events were triggered by enhanced asthenospheric mantle melting in two distinct arc-tectonic settings—a retreating slab and an advancing slab, respectively. Our results demonstrate that dynamic changes in the subducting slab were primary controls in triggering mantle flare-up events in the Phanerozoic Zealandia Cordillera.

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Engineering-Geological Studies Of The Territory, Soils Of Foundation And Foundations Of The Architectural Monument Of The "Melnikov’s House" In Moscow

Promyshlennoe i Grazhdanskoe Stroitel stvo ◽

10.33622/0869-7019.2019.05.41-51 ◽

2019 ◽

pp. 41-51

Keyword(s):

Working Condition ◽

Overlying Water ◽

North East ◽

The North ◽

Geological Processes ◽

Architectural Monument ◽

Geological Conditions ◽

Zone Of Influence ◽

Complex Engineering ◽

Building Engineering

On the basis of engineering and design surveys of the building, engineering-geological and geophysical studies of the soils of the territory conducted by the article authors, as well as with due regard for the results of studies conducted on this territory by other authors, the features of the foundations, soils of their foundation and engineering-geological conditions of the territory of the Melnikov House are established. It is shown that the Melnikov house is located under complex engineering-geological conditions on the territory of high geological risk, in the zone of influence of tectonic disturbance. To the North of the area there is a zone of intersection of the observed disturbance with a larger disturbance that can have an impact on geological processes. To the North-East of the site of the Melnikov House, a sharp immersion of the roof of carbon deposits was revealed. It promotes groundwater seepage into limestone of the carbonate strata from overlying water-bearing sands and activation of processes of suffusion removal and sinkhole phenomena of the soil. The surveyed area is assessed as potentially karst-hazardous and adjacent to it from the North-East territory as karst-dangerous. In this regard any construction on the adjacent territory can provoke activation of sinkhole phenomena on the surface. The foundations of the building are basically in working condition. Existing defects can be eliminated during repair. The foundation soils mainly have sufficient bearing capacity. Areas of the base with bulk soil can be reinforced. However, when developing a project for the reconstruction of the building and its territory, it should be taken into account that the design of the Melnikov House does not provide for its operation on the loads at the formation of sinkholes.

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METHODS OF FORECAST CALCULATION OF GROUND WATER BACKWATER IN THE ZONE OF HYDRAULIC STRUCTURES INFLUENCE

Prirodoobustrojstvo ◽

10.26897/1997-6011-2020-5-109-116 ◽

2020 ◽

pp. 109-116

Author(s):

N.P. KARPENKO ◽

◽

M.A. SHIRYAEVA

Keyword(s):

Numerical Model ◽

Computer Program ◽

Ground Water ◽

Programming Language ◽

Hydraulic Structure ◽

Hydraulic Structures ◽

Software Model ◽

Computational Program ◽

Specific Object ◽

Zone Of Influence

The purpose of the work is to consider methods for calculating the forecast of groundwater backwater in the zone of influence of hydraulic structures. The analysis of analytical dependences of calculation of the forecast of groundwater backwater for various calculation schemes is carried out. For a homogeneous scheme of the geofiltration structure, a numerical model is proposed and a computational program for calculating the groundwater backwater is developed. It allows calculating the groundwater backwater from the channel at any time in the discrete mode. To simplify the solution of the problem of calculating the groundwater backwater, a computer program was created in the programming language Phyton Version 8.3 which quickly solves this hydrogeological problem. A possible range of geofiltration parameters is proposed for calculating the groundwater backwater near main channels. The adaptation and implementation of the software model was carried out for a specific object – the Bolshoy Stavropol channel-5, for which forecast calculations were made. The results of predictive calculations of groundwater backwater are the basis for the assessment of areas of possible flooding – the territory within which the level of ground water increases as a result of their backup by a hydraulic structure.

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Methodical and organizational aspects in designing sanitary protection zones for a group of enterprises or industrial centers as a toll for complex atmospheric air quality assessment

Russian Journal of Occupational Health and Industrial Ecology ◽

10.31089/1026-9428-2019-59-11-940-944 ◽

2019 ◽

pp. 940-944

Author(s):

S. Yu. Zagorodnov ◽

I. V. May

Keyword(s):

Air Quality ◽

Industrial Complex ◽

Design Work ◽

Atmospheric Air ◽

Protection Zones ◽

Industrial Enterprises ◽

Economic Entity ◽

Outer Border ◽

Zone Of Influence ◽

Environmental Measures

Introduction. Sanitary legislation of the Russian Federation provides for the organization of sanitary protection zones of industrial enterprises located in the industrial hub. However, the justification procedure, establishing and monitoring boundaries of a single sanitary zones not fully resolved. This determines the practice of organization by economic entities of individual zones separating production from residential development. This situation complicates the adequate assessment of real pollution, as well as the reasonable development of programs (plans) of environmental measures. Identification of the sources that create poor air quality and public health risks is becoming extremely problematic.The aim of the study is to develop and test recommendations for the organization and methodological support of the design of a single sanitary protection zone of a group of enterprises in the current urban development.Materials and methods. The object of the study is an industrial hub formed by 5 industrial enterprises and located on the territory of a large urban settlement with a population of more than 450 thousand people. The city administration carried out a number of organizational measures that ensured the simultaneous inventory of emissions of enterprises and the design of the general sanitary zone of the industrial complex. The design work was carried out in full accordance with the current regulatory framework.Results. The verified unified database of 102 sources of chemical emissions and 113 sources of noise provided the possibility of summary calculations and obtaining the most correct results for surface concentrations in the zone of influence of the industrial hub. The program of quality control of atmospheric air defining the contribution of each economic subject to carrying out researches is formed. This made it possible to ensure the control of all priority contaminants at the outer border of the sanitary zone and reduce the costs of each separate economic entity. Zones of responsibility of each enterprise within borders of a uniform sanitary zone for tasks of maintenance of the standard maintenance of the territory are allocated.Conclusions. The obtained results confirmed the feasibility of designing unified sanitary protection zones for economic entities located in the industrial hub.

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