Linear Belt Research Articles

Satellite gravity fields and the identification of accreted microplates

Small-scale lithospheric terranes (microplates) are important building-blocks of continental accretion but their presence is often obscured by subsequent plate-margin deformation events and by younger volcano-sedimentary covers. The geological fabric of the eastern Anatolian-Caucasian region results from the sequential accretion of lithospheric terranes against the southwestern continental margin of the Eurasian plate. Widespread sedimentary and volcanic covers conceal some of the principal tectonic boundaries in the region, and major uncertainties persist as to the number and extent of the various terranes.We determine whether the topographic height fits the expectance from crustal thickness, complying to the isostatic equilibrium. The input data of the study are the topography, the satellite derived gravity field, the geologic knowledge defining magmatic intrusions and tectonic terranes, arcs and sedimentary basins, the seismic Moho depth, and a seismic tomography model. We accomplish a topography-gravity regression analysis controlled by a seismic Moho model, which produces well defined positive and negative anomalies. Allowing for varying density contrast in lower crust, the topography is greatly in isostatic equilibrium and controlled by the crustal thickness, that is topographic uplift has evolved proportionally to crustal thickening. The average density contrast in lower crust is between 200 and 300 kg/m3 for the orogenic belt, with local exceptions.The inversion of the prominent positive linear anomalies of the regional gravity field defines discrete crustal density inhomogeneities, which can be interpreted as related to specific tectonic events, thus placing cogent constraints on the accretionary history and the overall anatomy of the eastern Anatolian-Caucasian lithospheric agglomerate. Three linear belts of intracrustal increased density are found along (i) the Greater Caucasus, (ii) the Lesser Caucasus, and (iii) a previously unidentified parallel belt ca. 80 km south of the Lesser Caucasus. The latter gravity anomaly clearly delineates for the first time the southwestern margin of the South Armenian Block, a lithospheric element (microplate) whose existence has long been a matter of debate.

The Sierra Madre Oriental Orocline: Paleomagnetism of the Nazas Province in NE Mexico

AbstractCurved mountain belts are spectacular natural features that contain crucial 3D information about the tectonic evolution of orogenic systems in the absence of other kinematic markers. The Mesozoic units exposed in the Mexican Fold and Thrust Belt in northeastern Mexico show a striking curvature, whose kinematic history has not been studied. The existing tectonic models of the region simply assumed the shape of the tectonic units as an inherent feature to the orogen. We investigated the kinematic history of this curvature through paleomagnetism and rock magnetism analyses, coupled with an exhaustive review of available published literature. The studied data sets indicate a protracted history of (re)magnetizations that occurred during the Late Jurassic‐Paleocene times at least during the Late Jurassic, Cretaceous and early Eocene. More significantly, they show significant counterclockwise rotations in the northern flank of the curvature and moderate clockwise vertical axis rotations along its southern flank. This data set suggests that the Sierra Madre Oriental was a linear belt that experienced oroclinal bending or buckling during the Cretaceous to early Eocene period (120–50 Ma).

Salinity Fronts in the South Atlantic

Monthly climatology data for salinity fronts in the South Atlantic have been created from satellite SMOS sea surface salinity (SSS) measurements taken from 2011–2019, processed at the Barcelona Expert Center of Remote Sensing (BEC), and provided as high-resolution (1/20°) daily SSS data. The SSS fronts have been identified with narrow zones of enhanced horizontal gradient magnitude (GM) of SSS, computed using the Belkin–O’Reilly algorithm (BOA). The SSS gradient fields generated by the BOA have been log-transformed to facilitate feature recognition. The log-transformation of SSS gradients markedly improved the visual contrast of gradient maps, which in turn allowed new features to be revealed and previously known features to be documented with a monthly temporal resolution and a mesoscale (~100 km) spatial resolution. Monthly climatologies were generated and analyzed for large-scale open-ocean SSS fronts and for low-salinity regions maintained by the Rio de la Plata discharge, Magellan Strait outflow, Congo River discharge, and Benguela Upwelling. A 2000 km-long triangular area between Africa and Brazil was found to be filled with regular quasi-meridional mesoscale striations that form a giant ripple field with a 100 km wave length. South of the Tropical Front, within the subtropical high-salinity pool, a trans-ocean quasi-zonal narrow linear belt of meridional SSS maximum (Smax) was documented. The meridional Smax belt shifts north–south seasonally while retaining its well-defined linear morphology, which is suggestive of a yet unidentified mechanism that maintains this feature. The Subtropical Frontal Zone (STFZ) consists of two tenuously connected fronts, western and eastern. The Brazil Current Front (BCF) extends SE between 40 and 45°S to join the subantarctic front (SAF). The STFZ trends NW–SE across the South Atlantic, seemingly merging with the SAF/BCF south of Africa to form a single front between 40 and 45°S. In the SW Atlantic, the Rio de la Plata plume migrates seasonally, expanding northward in winter (June–July) from 39°S into the South Brazilian Bight, up to Cabo Frio (23°S) and beyond. The inner Plata front moves in and out seasonally. Farther south, the Magellan Strait outflow expands northward in winter (June–July) from 53°S up to 39–40°S to nearly join the Plata outflow. In the SE Atlantic, the Congo River plume spreads radially from the river mouth, with the spreading direction varying seasonally. The plume is often bordered from the south by a quasi-zonal front along 6°S. The diluted Congo River water spreads southward seasonally down to the Angola–Benguela Front at 16°S. The Benguela Upwelling is delineated by a meridional front, which extends north alongshore up to 20°S, where the low-salinity Benguela Upwelling water forms a salinity front, which is separate from the thermal Angola–Benguela Front at 16°S. The high-salinity tropical water (“Angola water”) forms a wedge between the low-salinity waters of the Congo River outflow and Benguela Upwelling. This high-salinity wedge is bordered by salinity fronts that migrate north–south seasonally.

Hadgarh Greenstone Belt: An extension of Tomka Daitari Greenstone Belt, Singhbhum Craton, India

Peripheral volcano sedimentary belts around the nucleus of Singhbhum-Granite-Complex are a part of one of the oldest continental crusts, known as the Singhbhum Craton (SC). Deciphering mutual relationship among these volcano-sedimentary packages offers considerable challenges. Badampahar-Gorumahisani Belt (BG Belt), Tomka Daitari Belt (TD Belt) and Bonai-Kendujhar Belt (BK Belt) draping Singhbhum-Granite-Complex as long linear belts from east, south and west, have some certain difference, primarily in terms of lithology. While the sedimentaries of BG Belt is mainly chemogenic, BK Belt is dominated by terrestrial sediments and TD Belt contains the both. Available data suggests the younger age of BK Belt than the rest couple of belts. Between TD Belt and BG Belt, another volcano sedimentary belt, commonly known as Hadgarh Belt, is present and it is less studied. The present study aims to characterize the Hadgarh Belt based on lithology and structure, which indicates its similarity with TD Belt. Almost identical lithologies are manifested by these two volcano sedimentary sequences barring the fact that the Hadgarh Belt has minor dominance of metasediments over metavolcanics, which is in subequal proportion in Tomka-Daitari and sensustricto BIF bands are absent in Hadgarh Belt. Both the belts have undergone uniform polyphase deformation and metamorphism. In both the belts, volcano sedimentary sequence of IOG is overlain by less deformed younger Mahagiri Quartzites and they are separated by an angular unconformity, marked by an impersistent conglomerate horizon. The intermediate area also sustains the similarities in depositional and deformational history with respect to the TD and Hadgarh belts on either side. Petrological studies also invoke similar mineral assemblage in the two belts, which is also in corroboration with the petrochemistry of the litho-units concerned. All the data thus generated, shows that the area, in totality, was evolved in an island arc setting varying from deep to shallow marine environments and sequence of deformations, intrusion of ultramafics followed by granite are also similar. In a nut shell, Hadgarh Belt can be referred as an extended part of the TD Belt.

Reconstructing the Paleoproterozoic Heart of Nuna, from Fennoscandia to Northeastern Laurentia

Abstract Accurate palaeogeographical reconstructions of past supercontinents are necessary to test models of supercontinent cyclicity, secular variation in plate tectonics and mantle geodynamics. However, numerous factors limit our ability to reconstruct past supercontinents as is evident in the ongoing debates regarding the construction phase and geometry of Earth's most recent supercontinent, late Paleozoic to early Mesozoic Pangaea. An important factor in these debates, and a focus of our study is how best to palinspastically restore, in section and in plan-view, the orogenic belts along which supercontinents were stitched together. We utilize the orogenic belts spanning Baffin Island, Greenland and Fennoscandia that are inferred to record the assembly of the Paleoproterozoic supercontinent Columbia to test the accepted reconstruction of the Nuna core of Columbia. We show that as reconstructed in the Nuna model, each of Baffin Island, Greenland (with some complications) and Fennoscandia are characterized by an older cratonic backstop that gives way to younger accretionary complexes toward the inferred oceanic domain that lay to the south and which is inferred to have closed by subduction beneath northeastern Laurentia–Fennoscandia during Columbia assembly. This southward transition from cratonic backstop to accretionary orogen is a hallmark of upper plates in modern convergent plate margins and is consistent with the construction of the Columbia supercontinent, including its Nuna core, through plate tectonic processes, and provides a broad validation of the Nuna reconstruction and hence for Columbia as a whole. Map view curvature of the cratonic backstops is restricted to long wavelength, open bends consistent with the Archean crust having been characterized by significant lithospheric strength. The more accretionary southern portions of Nuna are, however, characterized by sinuous orogens that developed by oroclinal bending of formerly more linear belts, significantly complicating their palinspastic restoration and rendering detailed correlation of juvenile orogenic belts across Nuna problematic.

Crustal resistivity structures beneath the western flank across the Central Main Ethiopian Rift: Its implications for partial melt and pathways

The Wonji Fault Belt (WFB) and the Silti Debre Zeit Fault Zone (SDFZ) are two linear belts in the Central Main Ethiopian Rift (CMER) where recent magmatic and tectonic activities have been concentrated. To examine deep resistivity patterns, magma storage, and its path beneath the Earth's crust across the CMER, the researchers used a two-dimensional (2D) inversion model of magnetotelluric data. The time series magnetotelluric data ranging from 0.003125 to 1450.0 s were collected during >24 h of installations at 21 sites, with an average station separation of 2.5 km along a profile perpendicular to the rift from the western margin of the rift (near Butajira) to AdamiTulu (near the rift axis). This work describes the use of phase tensor analysis to determine the dimensionality and geoelectrical strike direction, as well as the estimation of geoelectric strike parameters and the 2D inversion model of MT data. The results of dimensionality analysis of the majority of our MT data show a small beta value (|β|<30) at low periods (nearly below 10 s), which indicates 1D or 2D structures, while at long periods (almost above 10 s), the data show 3D structures with a large value of |β| >30. However, from the results of the dimensionality analysis of MT data, the 2D inversion model is suitable to image the resistivity of subsurface structures. The dominant geo-electrical strike is estimated to be N150E using a Z-invariant and phase tensor azimuth. The 2D inversion model was performed after the MT data were rotated to the proper geoelectric strike direction of N150E. The desired 2D inversion of the resistivity model was obtained for the MT profile using joint inversion of TE (transverse electric) and TM (transverse magnetic) mode data with an RMS misfit of 1.11. The results of the 2D inversion model reveal partial melt and upper crustal fracture zone (fault). They are attributed to a large mass of batholithic or magmatic intrusion found at a depth of 12–22 km that is characterised by a resistivity of <5 Ωm. The partial melt extends beneath stations B07 to B11 along SDFZ with a horizontal width of approximately 10 km. It could be related to the source of heat for the Ashute and Aluto geothermal fields.

Landsat 8 and Alos DEM geological mapping reveals the architecture of the giant Mesoproterozoic Kunene Complex anorthosite suite (Angola/Namibia)

The quasi-monomineralic composition and huge spatial extent of massif-type anorthosites make detecting lithological regions and boundaries challenging. We use processed Landsat 8 OLI multispectral images and ALOS digital elevation models integrated with field and petrographic observations to characterize the architecture of the ≥17,000 km2 Mesoproterozoic Kunene Complex (KC) anorthosite suite in Angola and Namibia. Images of false colour composite bands 6, 4 and 1 and band ratios 4/2 (ferric minerals), 6/5 (ferrous minerals) and 6/7 (OH-bearing minerals), as well as assessment of the PCA and MNF matrices of eigenvectors and eigenvalues from Landsat 8 data using available spectral libraries, have substantially improved the interpretation of the Kunene Complex rock types and structures. The dataset shows that the reflectance signature of KC anorthositic rocks is primarily a function of the degree of metasomatism, which is most significant in olivine-poor rock types. The weathering intensity of the olivine-bearing anorthosite substrate is another control on the remote sensing signal.Our remote sensing and field-based approach has enabled us to divide the KC anorthosite suite into six distinct spectral and architecture domains and at least four distinct magmatic plutons when considering available high-precision geochronological data. The northernmost pluton (ca. 1380 Ma) of massive, olivine-bearing anorthosite shows distinct remote sensing signatures in the band ratio and MNF images marked by the dominance of OH-bearing and subordinate ferric minerals. The central pluton (1412–1400 Ma) is composed of NNE- to N-striking steeply dipping interlayered olivine-bearing and olivine-poor anorthosite, which correspond to ridges of dark-coloured, low albedo rocks with subordinate slightly oxidised ferrous mineral spectral signatures, and valleys of low albedo and OH-bearing mineral spectral signatures. A NNE-striking tectonic zone along a linear belt of KC granite gneiss separates the northern and central plutons. To the south is a NNW- to NNE-striking layered pluton (ca. 1390 Ma), marked by olivine-bearing anorthosite that forms ridges and metasomatized olivine-poor and pyroxene-bearing anorthosite that forms valleys. This domain is separated from the similarly layered and E–W-striking Zebra Lobe–Oryeheke anorthosite by a top-to-the north thrust zone. A small domain of ca. 1438 Ma olivine-bearing anorthosite sensu lato is situated to the SE of the main Kunene Complex.This work highlights the variability in layered and massive textures, the extent of metasomatism, and the importance of internal tectonic boundaries in the architecture of the Kunene Complex anorthosite suite. Our approach can be applied in other anorthositic terrains and large igneous bodies elsewhere on Earth, especially those where outcrop is poor, or access is inhibited.

Age and petrogenesis of mafic granulites from central Madurai block, south India: implications on regional tectonics

AbstractThe Precambrian Southern Granulite Terrane (SGT) of south India is well-known for the preservation of high- to ultrahigh-temperature (HT-UHT) granulites, prominently exposed in its central part forming a linear belt referred to as the Kambam UHT belt. This belt also hosts widespread occurrences of mafic granulites that are observed in close spatial association with the HT-UHT granulites. This study presents detailed petrology, geochemistry and geochronology of representative mafic granulites from the area to understand their petrogenesis and tectonic setting. The results demonstrate that mafic granulites are low- to medium-K tholeiites, with continental arc affinity, formed by the partial melting of a subduction-modified enriched mantle source. The composition of the parent mantle source is modelled with a spinel/garnet lherzolite contribution ratio between 100/0 and 70/30, suggesting the mixing of spinel and garnet bearing melts during asthenosphere upwelling. Zircon U–Pb geochronology of mafic granulites constrains their emplacement between 612 Ma and 625 Ma, that subsequently underwent metamorphism between 581 Ma and 531 Ma. This overlaps with the timing of HT-UHT metamorphism in the Kambam UHT belt bracketed between 593 and 532 Ma. Zircon Hf isotopic studies reveal parent magma generation from reworked melting sources involving Archean and Proterozoic components. These results propose an alternative heat source for the formation of HT-UHT granulites in the Kambam UHT belt which can be designated as a major terrane boundary within the SGT.

Deposition of sandstone (early Cambrian) above the Great Unconformity in the Sino-Korean Block, Gondwana: Control of antecedent topography

The global transition between the Precambrian and Phanerozoic eons in concert with rise in eustatic sea-level caused an important change in paleoenvironments, represented by sedimentary records above the Great Unconformity. In the Sino-Korean Block, Gondwana, the unconformity has been recognized by a boundary between various basement rocks and the overlying distinctive suite of sandstone (including conglomerate, conglomeratic sandstone, and mudstone) of the early Cambrian age. A plate tectonic reconstruction of the Cambrian-Ordovician succession in the northeast Asian continent reveals that the sandstone deposited largely in the eastern part of the platform (North China Platform), including the Taebaeksan and Pyeongnam basins. In the western part of the platform, the basal sandstone is correlated to basal carbonate rocks of middle Cambrian age, forming a time-transgressive or diachronous unconformity. The disparity in sedimentary facies of the basal deposits overlying the Great Unconformity was primarily due to antecedent topography of the bounding continent: in the eastern platform, the drainage area comprised high-relief Precambrian massifs, whereas in the western part, it comprised low-relief massifs. During the initial stage of sea-level rise, the eastern part of the platform formed progressively open shoreface and foreshore environments with localized embayments in which relatively coarse-grained gravelly sandstone deposited in fan-delta and tide-dominated environments. In the western platform, however, the supply of siliciclastic sediments was limited and the sandstone formed a relatively narrow linear belt of delta and distributary mouth bars and foreshore deposits. In the rest of the platform farther west, accommodation created by subsequent sea-level rise was filled with carbonate sediments. This study demonstrates that antecedent topography of the unsubmerged drainage area played a major role for the deposition of sandstone in the initial transgression stage, forming the Great Unconformity.

The Multiple Metamorphism of Mafic Granulites From the East Hebei Terrane, North China Craton: Insights Into the Transition of Tectonic Regimes

The East Hebei terrane from the North China Craton preserves the dome–and–keel structures, which was transected by a later linear belt in the north margin. Mafic granulites from the linear belt and domes record two groups of metamorphic ages at Neoarchean and Paleoproterozoic, but their accurate metamorphic peak conditions and paths have not been well addressed. Three samples of mafic granulites, including two-pyroxene granulite (JD15120), garnet-bearing two-pyroxene granulite (YC8-43), and garnet clinopyroxene granulite (JD1546), were documented for detailed metamorphic studies. Two-episode metamorphism can be recognized. The first-episode recovered from JD15120 and YC8-43 is represented by peak assemblage of medium-grained clinopyroxene, orthopyroxene, amphibole, plagioclase, and ilmenite, which yields ultrahigh temperature (UHT) conditions of 940–960°C at 7.5–8.5 kbar and 950–990°C at 8 kbar, respectively, constrained by contours of the maximum anorthite (XAn) in plagioclase cores. The post-peak evolution is dominated by cooling with decompression, constrained mostly from the measured core-to-rim decreasing XAn in plagioclase. By contrast, the second-episode overprinting is recognized in all samples, but exhibits varying textures. In garnet-bearing samples (YC8-43 and JD1546), the overprinting assemblages are characterized by poikilitic garnet that occurs either as coronae around the first-episode pyroxenes, forming “red-eye socket” textures, or as grains in equilibrium with tiny-grained clinopyroxene, plagioclase, amphibole, rutile, and quartz, forming high-pressure (HP) granulite assemblages. These HP granulite assemblages show peak conditions of ∼12 kbar/860°C and ∼12.6 kbar/835°C, constrained by contours of the maximum grossular (XGrs) in garnet cores and the minimum XAn in plagioclase cores. The post-peak evolution is dominated by isothermal decompression, constrained from the outward decreasing XGrs in garnet and increasing XAn in plagioclase. LA-ICP-MS U-Pb zircon dating on JD15120 and JD1546 suggests two metamorphic ages of ∼2.49 Ga and ∼1.78 Ga, being considered to be correlated with the UHT and HP granulite metamorphism, respectively. Tectonically, the late Neoarchean UHT granulite metamorphism may correlate a vertical sagduction regime, whereas the late Paleoproterozoic HP granulite metamorphism is favored to register the continental collision in the northern margin of the North China Craton. This study may have indications for the Neoarchean–Paleoproterozoic tectonic transition of the craton.

Hunter-Gatherer Settlement Patterns in the South-Central Mojave Desert: Perspectives from Emerson Lake, San Bernardino County, California

ABSTRACT This article briefly explores the archaeological signatures of Early through Late Holocene resource use and hunter-gatherer settlement patterns near Emerson Lake aboard the Marine Corps Air Ground Combat Center. Investigations of 156 localities along a linear belt of probable plant biomass modeled through Normalized Difference Vegetation Index assessments registered larger, richer, and more diverse assemblages containing significantly higher frequencies of resource-processing artifacts, such as flake tools and ground stone, nearer this belt than predicted by random distribution, suggesting that hunter-gatherer encampments, reflecting the utilization of recurring abundant seasonal biotic patches, targeted this belt. However, other than upticks in processing artifact numbers and proximity to the belt during the 1,000 years prior to European contact, archaeological assemblage profiles remain comparatively constant, implying little deviation in the way local hunter-gatherers utilized and settled around this landscape throughout the Holocene.

Modelling Kinetics of Extruded Fish Feeds in a Continuous Belt Dryer

Feed is the major inputs in aquaculture production which affects the development growth of aquaculture in the African continent. Extruded fish feeds are dried to desire moisture content to increase the shelf life. Conventional method of drying fish feeds had gained attention recently in Nigeria in order to reduce high cost of producing fish feeds. However, this method is still grossly underutilized. Extrude floating fish feed was dried using continuous belt dryer at drying air temperature from 60°C to 100°C at an interval of 10°C, velocity of air using for drying from 0.8 m s-1 to 1.0 m s-1 at an interval of 0.1 m s-1 using a constant linear belt speed of 50 m s-1. Various moisture contents gotten at different conditions were changed to ratio of the dried extrudates moisture so as to obtain curves of drying by plotting the ratio of moisture against time. The dried extrudates behaviour was determined by fixing the drying curves with five well known models. Model with high determination coefficient and low reduced chi-square, low standard error, low value of least square and low standard deviation error (SEE) was used as best model. Midilli et al model was found suitable in describing the behaviour of extruded fish feed during drying. The temperature of air used for drying was discovered to have a major influence on the drying kinetics of the extruded fish feeds based on the conditions of this experiment.

Modelling Kinetics of Extruded Fish Feeds in a Continuous Belt Dryer

Feed is the major inputs in aquaculture production which affects the development growth of aquaculture in the African continent. Extruded fish feeds are dried to desire moisture content to increase the shelf life. Conventional method of drying fish feeds had gained attention recently in Nigeria in order to reduce high cost of producing fish feeds. However, this method is still grossly underutilized. Extrude floating fish feed was dried using continuous belt dryer at drying air temperature from 60°C to 100°C at an interval of 10°C, velocity of air using for drying from 0.8 m s-1 to 1.0 m s-1 at an interval of 0.1 m s-1 using a constant linear belt speed of 50 m s-1. Various moisture contents gotten at different conditions were changed to ratio of the dried extrudates moisture so as to obtain curves of drying by plotting the ratio of moisture against time. The dried extrudates behaviour was determined by fixing the drying curves with five well known models. Model with high determination coefficient and low reduced chi-square, low standard error, low value of least square and low standard deviation error (SEE) was used as best model. Midilli et al model was found suitable in describing the behaviour of extruded fish feed during drying. The temperature of air used for drying was discovered to have a major influence on the drying kinetics of the extruded fish feeds based on the conditions of this experiment.

Frequency analysis of transversal vibrations of belt drives with time‐varying belt lengths

AbstractThe dynamic positioning accuracy and the smoothness are key aspects of linear belt drives where vibrations have a negative impact. A FE‐Model, based on a one‐dimensional analytical model of the belt, is derived to study the respective effects for different parameters. The model considers the dominant transverse deflection and a quasi‐static assumption for the longitudinal deformation. The possibility to consider various time‐varying belt lengths, the belt mass, stiffness and tension force is an essential part of the modeling. The non‐linear cable effect is demonstrated by comparison with the linearized solution. Vibrations for the cases of constant and variable belt length are investigated and compared to common in literature used approximation formulas for the resonance frequencies of such systems. The influence on positioning deviations and the use of vibration reduction techniques considering the different belt sections of the linear drive can be derived from the computed results and are topics for future research.

Indentation rolling resistance in pipe conveyor belts: a review

In this paper, a detailed literature review of indentation rolling resistance (IRR) in pipe belt conveyors is provided. Pipe belt conveyors offer an alternative to overcome the technical limitations of trough belt conveyors. However, pipe belt conveyor systems are more complex than trough belt conveyors, and the system’s life cycle can be significantly affected by some important technical aspects. Based on analytical formulations deduced from Jonkers to Rudolphi and the mathematical models used for pipe belt conveyors with regard to IRR, the influence of variables such as belt speed, vertical load, back cover thickness, idler radius, temperature, panel spacing, transverse stiffness, number of cycles, filling degree, and linear belt mass is discussed. The dimension standards for belt conveyors are shown, as well as relevant experimental methods currently available for measuring the IRR. Several main belt manufacturers of low rolling resistance compounds are noted.

Development and assessment of belt-drive seedlings transmission device for fully-automatic vegetable transplanter

The planting section of vegetable cultivation system practiced in China is moving rapidly in the direction of computerized transplanting. While seedlings metering device is considered a bottleneck in sense of its application in tunnel farming. Therefore, a novel type of belt drive seedlings transmission device has been designated by considering the requirements of fully-automatic transplanter. Further, the control system of device has also realized in this investigation. The overall assemblage of the device consisted of a supporting frame, linear belt actuator equipped with 57HS22 stepping motor, cups assembly, two photoelectric sensors, brake wires, pneumatic air cylinder, and linear slider rail. The positioning accuracy examination at delivery points and the success transmission rate assessment of the linear transmission device were carried out at different frequencies of the motor. The outcomes of positioning accuracy examination indicated that positioning error at both delivery points was gradually increasing with gradual increment in motor frequency. The maximum positioning error was 7.26 mm at the maximum corresponding frequency of 1600 Hz which satisfied the requirement of cups position. The required value of 60 seedlings per minute was achieved at the frequency of 1500 Hz and corresponding success transplanting rate was also 95%. Base on experimental outcomes indicated that this design structure meets the requirements of the seedling transmission at the pulse frequency of 1500 Hz.

Mesozoic Metallogenesis of Peru: A Reality Check on Geodynamic Models

Abstract The Andean Cordillera is generally regarded as the product of easterly subduction of oceanic lithosphere below South America since the Late Triassic, but recent syntheses have challenged this paradigm. In one model, W-dipping oceanic subduction pulls the continent west until it collides with a ribbon continent that now forms the coastal region and Western Cordillera of the Peruvian Andes. A second model involves westerly oceanic subduction until 120 to 100 Ma, without the involvement of a ribbon continent, to explain deep, subducted slabs revealed by mantle tomographic images. Both assume that “Andean-style” E-dipping subduction did not exist during the Jurassic and Early Cretaceous. Another model, also involving mantle tomography, assumes that a back-arc basin opened inboard of the trench between 145 and 100 Ma, displacing the E-dipping subduction zone offshore without changing its polarity. This article examines the implications of these hypotheses for southern Peruvian metallogenesis during the Mesozoic, when marginal basins opened and closed and were thrust eastward and then were intruded, between 110 and ~50 Ma, by a linear belt of multiple plutons known as the Coastal Batholith. The earliest mineralization in southern Peru is located on the coast and comprises major iron oxide and minor porphyry copper deposits emplaced between 180 and 110 Ma. This was followed by Cu-rich iron oxide copper-gold deposits and a large Zn-rich volcanogenic massive sulfide (VMS) deposit between 115 and 95 Ma, then minor porphyry Cu deposits at ~80 Ma. A second episode of localized VMS mineralization followed at 70 to 68 Ma, then a group of at least five giant porphyry Cu-Mo deposits in southernmost Peru formed between 62 and 53 Ma. The conventional model of Andean-style subduction, which explains many features of Mesozoic Andean metallogenesis in terms of changing plate vectors and velocities, is a poor fit with mantle tomographic anomalies that are thought to record the paleopositions of ancient trenches. A ribbon-continent model requires some plutons of the Coastal Batholith to have been separated from others by an ocean basin. West-dipping oceanic subduction does not account for Jurassic mineralization and magmatism in southern Peru. A model involving a back-arc basin that opened inboard of the existing trench, forcing E-dipping subduction to retreat offshore between 145 and 100 Ma, seems to best explain the metallogenic and tomographic data.

Was the Pamir salient built along a Late Paleozoic embayment on the southern Asian margin?

While the northward convex Pamir salient has been interpreted to be a Cenozoic feature, resulting from terranes of the Pamir experiencing ∼300 km of northward translation relative to Tibet and Afghanistan during the India-Asia collision, structural evidence for large magnitudes of translation is generally lacking. We focus on the geology of the Northern Pamir, which forms the outer margin of the salient, to argue that the Pamir salient has not experienced significant northward translation as has been suggested by several recent studies. We then present evidence based on new detrital zircon results that the Pamir salient may be an inherited feature from the Late Paleozoic southern margin of Asia. Kinematic endmember models of northward translation of the Pamir predict either ∼300 km of arc-parallel extension (radial thrusting model) or truncation of geologic terranes at the margins of the salient by strike-slip faults (transfer faulting model). However, both models are inconsistent with the regional geology and structural evolution, which shows minimal extension along outer arc of the Pamir (∼50 km) and no clear truncation or thinning of geologic terranes that make up the Northern Pamir. Regarding the origin of the Pamir salient, a pronounced change in detrital zircon age signature of the Northern Pamir from west to east suggests the regions were not directly connected (i.e. part of a continuous linear belt), and were sourced from distinct cratons. Further, an absence of Triassic arc/forearc flysch deposits and arc plutons along WNW portion of the Northern Pamir suggests the possibility of a transform boundary segment along the Triassic Paleo-Tethys oceanic subduction zone. Based on these observations, we suggest an embayment existed between Tarim and Karakum Cratons after their amalgamation to the southern margin of Asia in the Early Permian. During the Late Triassic, colliding Cimmerian Gondwanan terranes (Central-Southern Pamir) filled in the embayment, resulting in the northward deflection in the trace of the Paleotethyan suture zone and Gondwanan terranes and the current arcuate geometry of the Pamir. Subsequent Cenozoic northward translation of the Pamir is interpreted to be only ∼50 km, no more than ∼80-100 km, and may be coupled with northward translation of northwestern Tibet and northeastern Afghanistan.

Olivine-induced viscous anisotropy in fossil strike-slip mantle shear zones and associated strain localization in the crust

SUMMARYWe propose that strain localization in plate interiors, such as linear belts of intraplate seismicity, may arise from spatial variations in viscous anisotropy produced by preferred orientation of olivine crystals (CPO or texture) inherited from previous deformation episodes in the lithospheric mantle. To quantify this effect, we model the deformation of a plate containing a fossil strike-slip mantle shear zone at different orientations relative to an imposed horizontal shortening, but no initial heterogeneity in the crust. The fossil shear zone is characterized by different orientation and intensity of the olivine CPO relatively to the surrounding mantle, which is isotropic in most simulations. The anisotropy in viscosity produced by the CPO, which remains fixed throughout the simulations, is described by an anisotropic (Hill) yield function parametrized based on second-order viscoplastic self-consistent (SO-VPSC) models. The results indicate that lateral variations in viscous anisotropy in the mantle affect the strain distribution in the entire lithosphere. Reactivation of the strike-slip mantle shear zone and strain localization in the crust above it occur for horizontal compression at 35–55° to the fossil shear plane, with a maximum at 45°. The magnitude of strain localization depends on (i) the contrast in viscous anisotropy and, hence, on the variations in CPO orientation and intensity in the mantle, (ii) the boundary conditions and (iii) the feedbacks between mantle and crustal deformation. For a strong olivine CPO, when the boundary conditions do not hinder shear parallel to the fossil mantle shear zone, strain rates within it are up to a factor 30 higher than in an isotropic surrounding mantle or up to a factor 200 when the surrounding mantle is anisotropic, which results in strain rates up to a factor 10 or up to a factor 100 higher in the crust right above the fossil shear zone. Frictional weakening in the crust faults increases strain localization in the entire lithospheric column. High strength contrasts between the mantle and the ductile crust result in less efficient mechanical coupling, with strong localization in the mantle and lower crust, but weak in the brittle upper crust. Decrease in the crust–mantle strength contrast enhances the coupling and produces more homogenous strain distribution with depth, as well as a time-dependent evolution of strain localization, which reaches a peak and decreases before attaining steady-state. Comparison of seismic anisotropy, regional stress and focal mechanism data in linear arrays of intraplate seismicity, like the New Madrid and South Armorican seismic zones, to our models' predictions corroborates that olivine CPO preserved in fossil lithospheric-scale shear zones may be key for the development of such structures.

From Mesoarchean drips to modern–style tectonics in the Carajás Province, Amazonian Craton

The beginning of modern–style plate tectonics on Earth is not a consensus, but many authors suggest that it happened transitionally, from 3.2 to 2.5 Ga. In the Amazonian Craton, Brazil, the contrasting crustal architecture of the Rio Maria and the Carajás domains is marked by dome–and–keel and linear belt, respectively, which may represent a shift in the tectonic styles along the Mesoarchean to Neoarchean transition. Here, we discuss this hypothesis combining existing literature and an interpretation of airborne geophysical data for the Caracol Dome. This Archean TTG (Trondhjemite–Tonalite–Granodiorite) Dome shows a concentric lithological variation, with older 2.97–2.96 Ga trondhjemites at the edges and younger 2.95–2.92 Ga tonalites within the inner parts. The Caracol Dome exhibits a similar magmatic evolution to other Archean domes worldwide (e.g., Yalgoo and Mt. Edgar Domes), commonly interpreted as the record of vertical tectonics (e.g., drip–tectonics). However, the subsequent geological record in the Carajás Province is more likely related to the onset or transition to modern–style tectonics, such as large continental shelf sedimentation (Carajás Basin), steeply dipping linear shear zones with 2.76–2.73 Ga syn–tectonic intrusions and Neoarchean iron oxide–copper–gold (IOCG) mineralization. Finally, late Neoarchean to Paleoproterozoic tectonic events with new (and/or remobilized) IOCG deposits are also recorded in the Carajás Province.