Eastern Block Research Articles

Paleoproterozoic medium to high pressure metamorphism in the Wanzi supracrustal association, Trans-North China Orogen: New insights from the gedrite-bearing gneiss, gedrite-free gneiss, and amphibolite

The Wanzi supracrustal association locates in the Fuping Complex, middle Trans-North China Orogen, and it was generally considered before as a lithological unit that underwent medium pressure metamorphism. The newly discovered gedrite-bearing gneiss, gedrite-free gneiss, and amphibolite of the Wanzi supracrustal association show abundant mineral assemblages with complex reaction textures, which are critical clues to retrieve the metamorphic evolution of this area. Gedrite-bearing/free gneiss samples mainly consist of garnet porphyroblast plus matrix minerals including biotite, kyanite, sillimanite, staurolite, ±gedrite, plagioclase, quartz, as well as accessory minerals such as ilmenite, magnetite, apatite, monazite, and zircon. Amphibolite samples are generally composed of garnet porphyroblast plus matrix minerals amphibole, ±biotite, plagioclase, quartz, as well as accessory minerals including ilmenite, magnetite, and zircon. Two to four generations of metamorphic mineral assemblages formed at the prograde (M1), peak (M2), and retrograde (M3-M4) stages have been identified from these samples, recording clockwise P-T paths including sequential near-isothermal decompression (ITD) and near-isobaric cooling (IBC) segments, indicative of convergence tectonic settings. The peak P-T conditions of these samples are different, ranging from 8.2 to 13 kbar and 695 to 822 °C. SIMS/SHRIMP U-Pb dating of metamorphic zircon yields 207Pb/206Pb age of 1838–1821 Ma, representing the metamorphic event. Combined with the previous data, the Wanzi supracrustal association is inferred to have undergone middle to high pressure metamorphism during 1.84–1.82 Ga, which was involved in the subduction and/or collision event between the Western and Eastern Blocks and led to the final assembly of the North China Craton.

Temperature and timing of ductile deformation of the Longquanguan shear zone, Trans-North China Orogen

Determination of temperature conditions and timing of ductile shearing is important in understanding the deformation mechanisms and tectonic evolution. The Longquanguan shear zone locates in the middle section of the Trans-North China Orogen, extending ~ 100 km long in NNE-SSW direction and exposing abundant granitic and granodioritic mylonites, characterized by well-developed NW-dipping mylonitic foliation and penetrative NW-plunging mineral stretching lineation. The mylonite exhibits regionally heterogeneous mechanisms of dynamic recrystallization, dominated by subgrain rotation. Ti-in-quartz (TitaniQ) geothermometer was applied to assess the deformational temperature along five profiles across this shear zone. In the northern part of this shear zone, quartz ribbons of the three narrower profiles display relatively homogeneous Ti content and record similar temperatures of 474–505 °C, 500–539 °C, and 492–521 °C, respectively. In the southern part, quartz ribbons of the two wider profiles show eastward increasing Ti content and record temperature increasing from 440 to 557 °C, and from 461 to 553 °C, respectively. A temperature gradient is estimated to be 20–25 °C/km, which possibly relates to the geothermal gradient between the hanging wall and the footwall. The shear zone, along with the temperature gradient narrows out to the north, possibly resulted from differential erosion/denudation. The hornblende and mica 40Ar/39Ar age data indicate that the ductile deformation occurred at ~ 1.85–1.80 Ga, followed by quick cooling occurred at 1.83–1.78 Ga. Therefore, the Longquanguan shear zone records ductile shear deformation, which possibly occurred during the collision between the Western and Eastern Blocks of the NCC in the Late Paleoproterozoic.

Tectono-metamorphic evolution of the proto-Andean margin of Gondwana: Evidence of internal high-grade metamorphism along the northern portion of the Famatinian orogen, Sierra de Aconquija, Sierras Pampeanas Orientales, Argentina

The present work gives a detailed analysis of the metamorphic and structural evolution of the back-arc portion of the Famatinian Orogen exposed in the southern Sierra de Aconquija (Cuesta de La Chilca segment) in the Sierras Pampeanas Orientales (Eastern Pampean Sierras). The Pampeanas Orientales include from north to south the Aconquija, Ambato and Ancasti mountains. They are mainly composed of middle to high grade metasedimentary units and magmatic rocks.At the south end of the Sierra de Aconquija, along an east to west segment extending over nearly 10 km (Cuesta de La Chilca), large volumes of metasedimentary rocks crop out. The eastern metasediments were defined as members of the El Portezuelo Metamorphic–Igneous Complex (EPMIC) or Eastern block and the western ones relate to the Quebrada del Molle Metamorphic Complex (QMMC) or Western block. The two blocks are divided by the La Chilca Shear Zone, which is reactivated as the Río Chañarito fault.The EPMIC, forming the hanging wall, is composed of schists, gneisses and rare amphibolites, calc– silicate schists, marbles and migmatites. The rocks underwent multiple episodes of deformation and a late high strain-rate episode with gradually increasing mylonitization to the west. Metamorphism progrades from a M1 phase to the peak M3, characterized by the reactions: Qtz + Pl + Bt ± Ms → Grt + Bt2 + Pl2 ± Sil ± Kfs, Qtz + Bt + Sil → Crd + Kfs and Qtz + Grt + Sil→ Crd. The M3 assemblage is coeval with the dominant foliation related to a third deformational phase (D3).The QMMC, forming the foot wall, is made up of fine-grained banded quartz – biotite schists with quartz veins and quartz-feldspar-rich pegmatites. To the east, schists are also overprinted by mylonitization. The M3 peak assemblage is quartz + biotite + plagioclase ± garnet ± sillimanite ± muscovite ± ilmenite ± magnetite ± apatite.The studied segment suffered multiphase deformation and metamorphism. Some of these phases can be correlated between both blocks. D1 is locally preserved in scarce outcrops in the EPMIC but is the dominant in the QMMC, where S1 is nearly parallel to S0. In the EPMIC, D2 is represented by the S2 foliation, related to the F2 folding that overprints S1, with dominant strike NNW – SSE and high angles dip to the E. D3 in the EPMIC have F3 folds with axis oblique to S2; the S3 foliation has striking NW – SE dipping steeply to the E or W and develops interference patterns. In the QMMC, S2 (D2) is a discontinuous cleavage oblique to S1 and transposed by S3 (D3), subparallel to S1. Such structures in the QMMC developed at subsolidus conditions and could be correlated to those of the EPMIC, which formed under higher P-T conditions. The penetrative deformation D2 in the EPMIC occurred during a prograde path with syntectonic growth of garnet reaching P-T conditions of 640°C and 0.54 GPa in the EPMIC. This stage was followed by a penetrative deformation D3 with syn-kinematic growth of garnet, cordierite and plagioclase. Peak P-T conditions calculated for M3 are 710°C and 0.60 GPa, preserved in the western part of the EPMIC, west of the unnamed fault.The schists from the QMMC suffered the early low grade M1 metamorphism with minimum PT conditions of ca 400°C and 0.35 GPa, comparable to the fine schists (M1) outcropping to the east. The D2 deformation is associated with the prograde M2 metamorphism. The penetrative D3 stage is related to a medium grade metamorphism M3, with peak conditions at ca 590°C and 0.55 GPa.The superimposed stages of deformation and metamorphism reaching high P-T conditions followed by isothermal decompression, defining a clockwise orogenic P-T path. During the Lower Paleozoic, folds were superimposed and recrystallization as well as partial melting at peak conditions occurred. Similar characteristics were described from the basement from other Famatinian-dominated locations of the Sierra de Aconquija and other ranges of the Sierras Pampeanas Orientales.

The Late Paleoproterozoic A-Type Granites in the Jiao-Liao-Ji Orogenic Belt, North China Craton: Petrogenesis and Implications for Post-Collision Extension

The Paleoproterozoic Jiao-Liao-Ji Orogenic Belt is a part of the Eastern Block, North China Craton. The Shuangcha rock mass has been recently recognized in Laohe group of Jiao-Liao-Ji Orogenic Belt, and it consists of mainly porphyritic monzonitic granite and porphyritic K-feldspar granite. We present detailed studies of petrography, geochronology and geochemistry of Shuangcha rock mass to constrain the petrogenesis and tectonic evolution features of the Jiao-Liao-Ji Orogenic Belt. The mineral of the Shuangcha granite consists of K-feldspar, plagioclase, quartz and a small amount of biotite ( 350 ppm) and 10,000Ga/Al ratios (average 2.69), which are typical features of A-type granite. The Shuangcha A-type granites can be further subdivided into A2-type subgroup based on some geochemical features, such as high Y/Nb ratios (0.99~3.14, average 1.84). Petrographic and geochemical studies have shown that the Shuangcha granites were the product of partial melting of quartzo-feldspathic rocks under a high temperature (>899°C), low pressure and anhydrous environment. Based on geochemical studies of Shuangcha granites, spatial and temporal distributions of regional magmatism and metamorphism records, the Jiao-Liao-Ji Orogenic Belt was in a typical post-collision extension setting in late Paleoproterozoic period (1.82~1.88 Ga) probably triggered by the slab breaks off.

TSS, Yield and Energetics of Stevia as Influenced by Nitrogen Levels and Spacing under Eastern U.P. Conditions

Background: Stevia is a natural sweetener plant with zero calorie content which is used as an alternative source of sugar. Stevioside extract from stevia is considered to be 300-350 times sweeter than sugar. It is safe for use by both diabetics and hypo glycaemics due to its low glycaemic index. Stevia has some bitter aftertaste along with sweetness due to the presence of some essential oils, tannins and flavonoids.Methods: Field experiment was conducted at Eastern Block of Crop Research Farm, Department of Agronomy, Naini Agricultural Institute, Prayagraj during Zaid 2018. The experiment was carried out in randomized complete block design comprising of three N levels i.e. 50, 75 and 100 kg N/ha and inter row spacing of 30, 40 and 50 cm with 20 cm of plant to plant spacing. The study was carried out to find out response of nitrogen levels and spacing on stevia.Result: Maximum plant height (51.24 cm), leaf area (4596.99 cm2) was observed with treatment 100 kg N ha-1 at 50 cm x 20 cm spacing and leaf area index (7.30), total soluble solids (TSS) (18.73 oBrix) was noticed with treatment 100 kg N ha-1 at 30 cm x 20 cm spacing, whereas the maximum Leaf number (342.52) was recorded with treatment 100 kg N ha-1 at 40 cm x 20 cm spacing. The results of this experiment revealed that increased dose of nitrogen with narrow spacing gave maximum quality.

Geochronology, geochemistry and petrogenesis of the Neoarchean magmatism in the Jiefangyingzi area, northern North China Craton: Implications for crustal growth and tectonic affinity

The Bayan Obo-Duolun-Chifeng-Kaiyuan fault is considered as the craton-orogen boundary between the northern North China Craton (NCC) and the Central Asian Orogenic Belt (CAOB). However, locations of this boundary from Duolun, Chifeng to Kaiyuan have not been well constrained. The Jiefangyingzi area northeast to Chifeng is located at the junction of the Bainaimiao arc belt and northern NCC, and has long been regarded as part of the Bainaimiao arc belt of the CAOB. This paper presents new LA-ICP-MS zircon U-Pb geochronological, whole-rocks geochemical and Nd-Hf isotopic data of some recently identified Neoarchean magmatic rocks from the Jiefangyingzi area. These rocks consist mainly of amphibolites, dioritic gneisses, quartz dioritic gneisses, tonalitic gneisses and trondhjemitic gneisses formed at 2569–2536 Ma and minor amphibole plagioclase gneisses formed at ca. 2640 Ma, and are distributed in an east–west belt that is about 13 km long and 1.5 km wide. Geochemical and Nd-Hf isotopic compositions suggest that the amphibolites were derived from partial melting of a depleted mantle that was metasomatized by subduction-derived fluids with significant crustal contamination, and the dioritic gneisses were generated by partial melting of mantle peridotite metasomatized by slab-melts. The quartz dioritic and tonalitic gneisses originated from high degree partial melting of the subducted oceanic crust with garnet-bearing amphibolite facies in the residue, while the trondhjemitic gneisses originated from low degree partial melting of the thickened mafic lower crust with eclogite facies in the residue due to underplating of mafic magmas. The occurrences of Neoarchean basement rocks, combined with previous Nd-Hf isotopic data of the late Paleozoic magmatic rocks, suggest that the Jiefangyingzi area has a tectonic affinity with the Eastern Block of the NCC rather than the CAOB, and the craton-orogen boundary between the northern NCC and the CAOB should be situated in places north to the Jiefangyingzi area. Our results support that the late Neoarchean (2.6–2.5 Ga) is also a period of crustal growth as well as extensive reworking of the 2.9–2.7 Ga ancient crust in the northwestern margin of the Eastern Block of the NCC. In addition, the transition from tonalite-trondhjemite-granodiorite (TTG) and other potassium-poor granitoid gneisses to crustal-derived potassium-rich granitoid gneisses at the end of Neoarchean (ca. 2.53 Ga) marked the initial cratonization of the NCC and ca. 2.53 Ga is a critical transformation period of maturation of the continental crust in the NCC.

Participatory forestry improves mangrove forest management in Kenya

Participatory forestry has been recognized as a tool for improving tropical forest management. The current study assessed the impacts of participatory forest management (PFM) on the structure and regeneration of a mangrove forest at Gazi Bay, Kenya. Data were collected along belt transects perpendicular to the waterline in both co-managed and state-managed mangrove forests. Basal area and standing density were significantly higher in the co-managed mangrove forests (16 m2/ha and 4 341 tree/ha) as compared to the state forests (eastern block 10.3 m2/ha and 2 673 trees/ha; western block 6.2 m2/ha and 2 436 trees/ha). There were significantly higher (p = 0.0068) densities of merchantable poles in community-managed as compared to state-managed forests. Natural regeneration patterns in community-managed and state-managed forests were deemed adequate to support the recovery of both forests. The results demonstrate that community participation contributes to improved management of mangrove forests and is in agreement with the principles of sustainable forest management.

Metamorphic history and Neoarchean–Paleoproterozoic crustal growth of the central Trans-North China Orogen: Evidence from granulite- to amphibolite-facies rocks of the Hengshan complex

The Trans-North China Orogen (TNCO) is a major Paleoproterozoic collisional orogen exposed within the North China Craton (NCC). The orogen has undergone a complex tectonic evolution, but its role in the growth of continental crust is contentious. High-grade metamorphic rocks may carry key information required to clarify these issues. Here, using petrography, mineral chemistry, and zircon U–Pb–Hf isotopes, we investigate a suite of Neoarchean–Paleoproterozoic high-grade metamorphic rocks in the Hengshan Complex within the central TNCO. Garnet-bearing mafic granulites and amphibolites occur as lenses or dikes within tonalite–trondhjemite–granodiorite (TTG) gneisses. Three stages of metamorphic mineral assemblages are identified in a mafic granulite from the northern Hengshan Complex: (1) the prograde assemblage is preserved as small plagioclase and apatite inclusions within garnet porphyroblasts; (2) the peak mineral assemblage is recorded by a high-Ca garnet core coexisting with clinopyroxene, plagioclase, hornblende, biotite, and quartz; and (3) the retrograde assemblage is represented mainly by vermicular symplectites of hornblende + plagioclase and plagioclase coronae surrounding low-Ca garnet rims. Phase equilibria modeling and conventional geothermobarometry suggest that the mafic granulite records a clockwise P–T path, including decompression and cooling from the granulite-facies peak (12.5–14 kbar and >750 °C) to amphibolite-facies conditions during retrogression (7.3–8.3 kbar and 615–721 °C). In contrast, the amphibolite in the southern Hengshan Complex preserves only amphibolite-facies assemblages (hornblende + plagioclase + quartz), consistent with the metamorphic pressures of <7.1 kbar and temperatures below 720 °C.Zircon U--Pb dating of magmatic zircons shows that the protoliths of the TTG gneisses and amphibolite were emplaced at ca. 2.5 and 2.1 Ga, respectively. The metamorphic zircons reveal ages of 1.92–1.80 Ga for the mafic granulite (weighted mean of ca. 1.87 Ga) and 1.92–1.83 Ga for the amphibolites (weighted mean of ca. 1.88 Ga). These 1.88–1.87 Ga metamorphic ages are interpreted to represent the time when the rocks cooled to the solidus. By comparing Paleoproterozoic metamorphic ages across the TNCO, we infer that the subduction–collision–amalgamation between the Western and Eastern Blocks of the NCC lasted from 1.95 to 1.80 Ga at least, marking the final cratonization of the NCC. The ca. 2.5 Ga magmatic zircons within the TTG gneisses show positive εHf(t) values (+0.49 to +7.12) with model ages of 2.8–2.7 Ga, suggesting that the protoliths were derived from the partial melting of Neoarchean juvenile mafic crust. Zircon Hf model ages (TDM = 2.1–2.0 Ga) of the mafic granulite may represent the approximate time at which the mafic magma was generated in the mantle. Thus, the Hengshan Complex within the central TNCO records two episodes of crustal growth at 2.8–2.7 and 2.1–2.0 Ga, respectively. To further understand the processes involved in crustal evolution, we reconstructed a layered crust model for the Hengshan Complex, and the layered crust was strongly influenced by Paleoproterozoic thermal events.

Origin of high-Cr stratiform chromitite in the Fangmayu Alaskan-type ultramafic intrusion, North China Craton

The study of chromite from chromitite-bearing layered intrusions can provide significant insights into their petrogenetic origin and tectonic setting. The Fangmayu Alaskan-type ultramafic intrusion in the North China Craton contains layered and massive chromitite associated with a serpentinized ultramafic suite. This study presents zircon and apatite geochronology, chromite mineral chemistry, platinum-group element (PGE) and Re-Os isotopic data for the purpose of constraining the origin, evolution, and composition of the Fangmayu chromitite parental melts. Zircon U-Pb data from the chromitites define various age populations, with oldest age component (>2.49 Ga) interpreted to represent xenocrystic grains incorporated from crystalline basement. A dominant age component (~2.42 Ga) may represent the age of magma emplacement. Ages in the range of 2375–2068 Ma likely represent variable partial radiogenic Pb-loss during subsequent thermal events. Zircon ages in the range of 1.96–1.90 Ga record metamorphic events, potentially related to the collision between the Eastern Block and Western Block in the North China Craton. Ages of 1.85–1.81 Ga likely represent zircon growth during retrograde metamorphic process in a post-collisional setting; near contemporaneous apatite (~1.8 Ga) tracks cooling through ~500 °C. High Fo contents in olivine (Fo90-92) and high Cr# in chromite (72–77) suggest a low Al2O3 ultramafic parental magma formed by a high degree of partial melting. However, total concentrations of PGEs are abnormally low, and the Re-Os system indicates multiple disturbances during later metamorphic events. Experimental data are used to recover the compositions of parental melts to the chromitite, the calculations yield parental melts with 10–11 wt% Al2O3 and 0.7–1.1 wt% TiO2, which define the arc and IAB affinity. The high Cr#s, low Al2O3 (8–10 wt%), and high TiO2 (0.58–0.96 wt%) contents of chromite, combined with calculated parental melt compositions, suggest that the parental magma of Fangmayu stratiform chromitites was a high-Ti island-arc basalt origin and formed within supra-subduction zone setting.

Late Neoarchean crustal growth under paired continental arc-back arc system in the North China Craton

The late Archean (~3.0–2.5 Ga) was a key period of continental growth globally, which is widely considered to reflect the onset of vigorous plate tectonic activity, although related continental growth modes remain contentious. Here we investigate a suite of late Neoarchean metavolcanic rocks from the southwest Qixia area of the Jiaobei terrane in the North China Craton. The rocks in this suite include amphibolites, clinopyroxene amphibolites, and hornblende plagioclase gneisses. We present zircon U-Pb isotopic data which indicate that the protoliths of these rocks formed during ~2549–2511 Ma.The (clinopyroxene) amphibolites correspond to meta-basaltic rocks, with some containing high modal content of titanite. These rocks show moderate to high FeOT (8.96–13.62 wt.%) and TiO2 (0.59–1.59 wt.%), flat to less fractionated REE patterns, and mildly negative Th, Nb, and Ta anomalies, resembling those of Fe-tholeiites. In addition, they display positive zircon ƐHf(t) values (+2.6 to +8.7), and are devoid of crustal contamination or fractional crystallization. Combined with the low Nb/Yb (mostly < 1.60) and (Hf/Sm)N (mostly < 0.95), low to moderate Th/Yb (0.08–0.54), and low V/Sc (5.53–9.19) ratios, these basaltic rocks are interpreted to have been derived from a relatively reduced and depleted mantle source that was mildly metasomatized by hydrous fluids. The hornblende plagioclase gneisses are meta-andesitic rocks, and occur interlayered with the basaltic rocks. They are transitional between tholeiitic and calc-alkaline rock series, and show fractionated REE patterns with evidently negative Th, Nb, and Ta anomalies. The depleted zircon ƐHf(t) values (+2.4 to +8.4) and quantitative chemical modeling suggest that the andesitic rocks were most likely generated by injection and mixing of juvenile felsic magmas with the tholeiitic basaltic magmas.In general, the chemical features and genesis of late Neoarchean meta-basaltic rocks in our study area resemble those of Mariana back-arc basin basalts. Combined with regional geological data, it is proposed that the Jiaobei terrane witnessed late Neoarchean crustal growth under a paired continental arc-back arc setting. On a regional context, we propose two distinct geodynamic mode of late Neoarchean continental growth across North China Craton (particularly the Eastern Block), i.e., (1) arc-continent accretion along northwestern part of the Eastern Block; and (2) paired continental arc-back arc system surrounding the ~3.8–2.7 Ga continental nuclei to the southeast.

Intracontinental extension and geodynamic evolution of the Paleoproterozoic Jiao-Liao-Ji belt, North China craton: Insights from coeval A-type granitic and mafic magmatism in eastern Liaoning Province

Abstract To better understand the origin and tectonic evolution of the Paleoproterozoic Jiao-Liao-Ji belt, North China craton, which have long been debated, we have conducted whole-rock geochemical and zircon U-Pb and Hf isotope analyses on Paleoproterozoic monzo(syeno)granitic gneisses and metamafic rocks from eastern Liaoning Province. The results indicate that these monzo(syeno)granitic gneisses and metamafic rocks formed concurrently at ca. 2.2–2.1 Ga. The monzo(syeno)granitic gneisses show geochemical features of A-type granites and were derived from dehydration melting of Archean tonalite-trondhjemite-granodiorite (TTG) with minor involvement of coeval mantle-derived magma in an extensional setting. The metamafic rocks are geochemically similar to mid-ocean-ridge basalt; they were generated by partial melting of isotope-depleted asthenospheric mantle in an intracontinental extensional setting and experienced crustal and continental lithospheric mantle contamination and fractional crystallization. Based on this study and published geological evidence, we propose the following tectonic model for the origin and geodynamic evolution of the Jiao-Liao-Ji belt: (1) Generation of high-density eclogitized lower crust accompanied by formation of voluminous Archean TTGs in the Eastern block; (2) intracontinental extension driven by upwelling of an asthenospheric hotspot along the Jiao-Liao-Ji belt in period of 2.20–2.0 Ga; (3) convergent orogenic processes between the Longgang block and Nangrim block governed by gravity-driven subduction of high-density eclogitized lower crust at ca. 1.95–1.85 Ga; and (4) postorogenic extension caused by delamination of the orogenic root and subsequent hot asthenospheric upwelling. This tectonic model can well explain the origin and geodynamic evolution of the Paleoproterozoic Jiao-Liao-Ji belt.

Geochemistry, geochronology and its geological implication of metamorphic rocks of the Jiehekou Group in the Lüliang complex

华北中部造山带是华北克拉通内部一条重要的前寒武纪碰撞造山带，该造山带的形成经历了一个漫长而复杂的演化过程。吕梁变质杂岩位于造山带中段，阜平杂岩西南，是透视华北克拉通早前寒武纪构造-热演化的一个重要窗口。本文针对该地区的界河口（岩）群黑云斜长片麻岩和含榴斜长角闪岩开展了系统的野外地质调查、显微岩石学、地球化学和变质年代学研究。结果表明，界河口（岩）群黑云斜长片麻岩的原岩多为富铝富钾的变泥质岩石，其物源主要来自长英质火成岩，形成于有演化岛弧发育的活动大陆边缘构造背景；含榴斜长角闪岩的原岩多数是拉斑玄武岩，源区来自于富集地幔，形成于岛弧构造环境。显微岩相学研究显示，含榴夕线黑云斜长片麻岩和含榴斜长角闪岩中均保留了早期进变质、峰期变质和晚期退变质三个阶段的变质矿物组合，且石榴子石边部多发育明显的白眼圈反应结构。其中，含榴夕线黑云斜长片麻岩的峰期矿物组合包括石榴子石、黑云母、夕线石、斜长石、石英和少量钾长石等；含榴斜长角闪岩的峰期矿物组合主要由石榴子石、角闪石、斜长石、磁铁矿和石英等组成。前期研究表明，二者的变质演化均记录了类似的顺时针近等温降压型的变质作用P-T轨迹，其峰期变质条件分别为>750℃/>7.0kbar和>750℃/>6.3kbar。本文LA-ICP-MS锆石U-Pb年代学研究表明，含榴黑云斜长片麻岩中记录了1928~1920Ma和1882~1855Ma两组变质年龄。结合中部带前人研究成果，本文推断吕梁变质杂岩的区域变质事件与华北克拉通东、西部陆块间的碰撞造山作用有关，该地区与碰撞阶段同期的峰期变质作用发生在1928~1920Ma，而后于1882~1855Ma期间进入与快速构造隆升有关的退变质作用阶段。;As an important Precambrian orogenic belt in the North China Craton (NCC), the Trans-North China Orogen (TNCO) was formed by the collision between the Eastern Block and Western Block through an extremely protracted evolution process. To the southwest of the Fuping complex in the central TNCO, the Lüliang metamorphic complex provides an ideal target for studying the Precambrian tectonothermal evolution of the NCC since many upper amphibolite- to granulite-facies metamorphic rocks of the Jiehekou Group were exposed in this area. Petrographic, geochemical and metamorphic geochronological studies were carried out on the biotite plagiogneisses and garnet-bearing amphibolites in this contribution. It was indicated that the protoliths of biotite plagiogneisses were mostly metapelites with high aluminium and potassium contents whose sedimentary provenances were demonstrated to have mainly come from felsic igneous rocks formed in an active continental margin environment. The protoliths of garnet-bearing amphibolites were tholeiite basalts from the enriched mantle, and formed in the island arc tectonic setting. Microscopic petrographic studies showed that there were three stages of mineral assemblages preserved in the garnet-bearing sillimanite-biotite plagiogneisses and amphibolites, including the prograde, peak and retrograde stages. The white-eye socket reaction microstructures commonly grew surrounding the garnet rims of these rocks. The peak assemblages of garnet-bearing sillimanite-biotite plagiogneisses mainly consist of garnet, biotite, sillimanite, plagioclase, quartz and some K-feldspar. Those of garnet-bearing amphibolites include garnet, amphibole, plagioclase, magnetite and quartz. Our previous studies showed that both two types of rocks revealed clockwise P-T paths ended with a near-isothermal decompression, and their peak conditions were > 750℃/>7.0kbar and >750℃/>6.3kbar, respectively. LA-ICP-MS zircon U-Pb dating in this study indicated that two groups of metamorphic ages, including 1928~1920Ma and 1882~1855Ma, were recorded in the garnet-bearing biotite plagiogneisses. Combined with previous metamorphic and geochronological studies of other complexes in the TNCO, the regional metamorphism occurred in the Lüliang complex was thought to be related to the orogenic collision between the Eastern Block and Western Block of the NCC. During this orogenic process, the metamorphic peak occurred at 1928~1920Ma in the Lüliang area, and then followed with 1882~1855Ma retrograde stages resulted by the rapid tectonic uplift after collision.

Polacy w Komisji Nadzorczej Państw Neutralnych w Korei

In the years 1950–1953, the Korean Peninsula was engulfed in a bloody war. Peace negotiations began as early as 1951, but the signing of the Armistice Agreement could not take place until July 27, 1953 in Pan Mun Jom, four months after the death of the USSR leader, Joseph Stalin. The Armistice Agreement closed an extremely tragic stage in Korean history, but also an extremely hot period of tense relations between Western and Eastern block. At the same time, the Korean Peninsula was artificially divided into two countries. Korea emerged from the war ruined. In order to implement the tasks assumed in the Armistice Agreement and to achieve the assumed goals, several bodies were established, incl. Neutral Nations Supervisory Commission, composed of representatives of four countries: Czechoslovakia, Switzerland, Sweden and Poland. The tasks of the Commission consisted in performing functions related to supervision, observation, inspection and investigations related to the replacement of military personnel, weapons and equipment, as well as in connection with the reported incidents in the demilitarized zone. Poles participate in its activities continuously until today.

Evropska unija i Ruska federacija - kratak istorijat odnosa od 1991. do 2021. godine

This article is dealing with international relations between EU and Russian Federation after falling of Berlin's wall and decline of communist regimes in countries of Eastern block. Author is trying to emphasize three periods. First period is from 1991. until 2000. During presidency of Boris Jeljcin in Russia. This period is reflected by declining of Russian power and stronger integration of Europe because of Treaties of Maastricht and Amsterdam. Second period is period of coming on power president Vladimir Putin and uprising of Russia. This period lasts until 2014. year, when relations were more-less stable, except conflict in Georgia. Third period is related to conflict in Ukraine in 2014. And energetic crisis in 2021. Conflict in Ukraine has shown that EU doesn't have force to stand from foreign policy of USA, which is reflected in actions of NATO. Author concludes article with hope that memory from two world wars will be enough strong for politicians from both sides to not let another world war, and they will find new ways to enhance international cooperation.

Effect of Zinc Fertilization on Physiological Parameters, Nutrient Uptake, Yield and Economics of Babycorn

A field experiment was conducted during late Kharif (September-November) of the year 2018 at Eastern Block Farm, Tamil Nadu Agricultural University, Coimbatore to find out the effect of agronomic bio-fortification with zinc on physiological parameters, nutrient uptake, yield and economics of babycorn under irrigated condition. The field experiment was laid in randomized complete block design with three replications. The treatments comprised of T1: No zinc (control), T2: Zinc Sulphate (ZnSO4) at 25 kgha-1 as soil application, T3: ZnSO4 at 37.5 kgha-1 as soil application, T4: Foliar spray of ZnSO4 at 0.5% on 20 and 40 DAS, T5: Foliar spray of ZnSO4 at 1.0% on 20 and 40 DAS, T6: ZnSO4 at 25 kgha-1 as soil application + foliar spray at 0.5% on 20 and 40 DAS, T7 : ZnSO4 at 25 kgha-1 as soil application + foliar spray at 1.0% on 20 and 40 DAS, T8: ZnSO4 at 37.5 kgha-1 as soil application + foliar spray at 0.5% on 20 and 40 DAS, T9: ZnSO4 at 37.5 kgha-1 as soil application + foliar spray at 1.0% on 20 and 40 DAS. Babycorn hybrid G-5414 was used to experiment with a plant spacing of 45 cm x 25 cm. The results showed that the combined application of zinc sulphate @ 37.5 kgha-1 with 0.5% foliar spray at 20 and 40 DAS recorded significantly higher Crop Growth Rate (CGR) (31.07, 30.83) gcm-2day-1, Relative Growth Rate (RGR) (110.25, 31.67) mgg-1day-1 and Net Assimilation Rate (NAR) (9.65, 4.54) mgcm-2day-1 at 25-45 DAS and 45 DAS - harvest intervals respectively. NPK uptake was recorded higher in (T8) and green cob yield was recorded higher in (T9) at harvest stage. Green fodder yield and higher benefit cost ratio was obtained higher with soil application of zinc sulphate @ 37.5 kgha-1 with 0.5% foliar spray at 20 and 40 DAS.

울산단층 동부 동부 지기의 융기율

울산단층 동부 동부 지기의 융기율

Paleoproterozoic metamorphism of metaultramafic rocks in the Miyun area, northeastern North China Craton

The Miyun area is located in the northwestern border of the Eastern Block of the North China Craton, where the metaultramafic rocks occur as intrusive bodies, some of which display cumulate features. The metaultramafic rock is (olivine-bearing) amphibole websterite and two generations of mineral assemblage have been identified: the magmatic mineral assemblage -consists- of clinopyroxene + orthopyroxene ± olivine ± spinel ± pyrite, whereas the subsequent metamorphic mineral assemblage comprises of hornblende + serpentine + chlorite + magnetite + zircon ± biotite ± calcite ± chromite ± calcite ± garnet. The metamorphic P-T conditions are estimated to be ~ 600–630 °C/4–6 kbar, which belongs to amphibolite facies and medium-P/T facies series. U-Pb dating of metamorphic zircon and 40Ar/39Ar dating of metamorphic hornblende indicate that the metamorphic event occurred at ~ 1.85–1.82 Ga. These data suggest that the Miyun area involved in the late Paleoproterozoic subduction-collision between the Eastern and Western Blocks, and the metamorphism possibly occurred at upper-middle crustal level with fluids.

New 40Ar/39Ar geochronology data of the Fuping and Wutai Complexes: Further constraints on the thermal evolution of the Trans-North China Orogen

The Trans-North China Orogen has witnessed the assembly of the Western and Eastern blocks of the North China Craton during Late Paleoproterozoic. Numerous studies have focused on the subduction/collision timing and metamorphic evolution of the Trans-North China Orogen, whereas the thermal evolution and exhumation history are still poorly understood. The Fuping and Wutai Complexes are widely exposed of middle- to high-grade metamorphic rocks, which are excellent regions to investigate the thermal evolution and exhumation history of the Trans-North China Orogen. Previous U-Pb geochronological data of metamorphic zircon and monazite suggest that the peak granulite facies metamorphism in the Fuping Complex occurred during 1.92–1.80 Ga, and peak amphibolite facies metamorphism in the northeastern part of the Wutai Complex happened at 1.85–1.82 Ga. Here we report newly obtained hornblende 40Ar/39Ar age of 1813–1806 Ma in the Fuping Complex, and biotite 40Ar/39Ar age of 1802–1786 Ma in the northeastern part of the Wutai Complex, which representing the cooling ages. Combined with previous thermochronological data, the cooling rate of 2.0–8.5 °C/Ma was obtained for the middle to southern segments of the Trans-North China Orogen, possibly suggesting a moderate to fast exhumation relative to other Proterozoic orogens.

A Textural and Mineralogical Study of the Shanzhuang Banded Iron Formation, Southeastern Margin of the North China Craton: Implications for the Overprint History of Hydrothermal Alteration and Supergenesis after Mineralization

AbstractThe newly discovered Shanzhuang BIF is hosted in the Shancaoyu Formation of the Taishan Group within the Eastern Block, southeastern margin of the North China Craton. The ores can be subdivided into three types in terms of mineral assemblages, corresponding to three types (I, II, III). The element concentration of the type I magnetite is similar to that of the type II magnetite, while the type III magnetite is similar to that of the schist. In general, magnetite and hematite grains from the ores show high concentrations of Mn (1317, 1162 ppm), Co (787, 1023 ppm), Al (2224, 2435 ppm) and Ti (540, 300 ppm), Whereas magnetite is depleted in Si (420 ppm) and hematite enriched in Si (1690 ppm). Detailed petrographic and mineral chemical analysis of magnetite, hematite, amphibole/hornblende and pyroxene, reveals that almost all the minerals occur as subhedral‐anhedral grains with pits and fractures, and the BIF is recrystallized to metamorphic assemblages of high amphibolite facies. Hornblende is highly enriched in Fe, Mg and Ca, but depleted in K and Na, mostly belonging to magnesiohornblende. In addition, the ratios of Mg/(Mg+Fe2+), Fe3+/(Fe3++Fe2+), Si/(Si+Ti+Al) and Al/Si are 0.48–0.64, 0.17–0.36, 0.79–0.88 and 0.14–0.27, respectively. It is suggested that hornblende is neither a typical magmatic origin nor a typical metamorphic. Pyroxene has the characteristics of high Ca and Fe, but low Ti and Al, with end‐member components En, Wo and Fs in the ranges of 25.22–28.64 wt%, 43.71–46.40 wt% and 24.51–27.62 wt%, respectively, belonging to clinopyroxene, and mostly diopside, might be formed during the prograde metamorphism in the absence of H2O. The carbonate such as dolomite‐ankerite series is probably a precursor mineral of the BIF deposit. Mass mineral chemical and structural characteristics indicate that the Shanzhuang iron deposit has been subjected to varying degrees of oxidized hydrothermal superimposed reformation, metamorphism, and supergenesis after mineralization, during which some elements have been migrated in some degree.

Modernism in the Case of Cultural Architecture in Yugoslavia

As a result of very strong and organised antifascist resistance on domestic territory during the World War II and historical conditions in the rest of Europe, new established socialist country Yugoslavia on geostrategic games was planned to stay part of the eastern block in the new division of post-war Europe. But just three years after the war Yugoslavian political establishment led by charismatic president Tito, despite the serious threats from USSR and Stalin, he decided to start with their own way of socialism based on self-management with reduced influence of the state into the economy, society and culture. The result was an atypical socialist system for that time, which was very open to the world, but especially to Western Europe and the USA. During the whole history, architecture was always the best representation of historical developments and social circumstances in different civilisations through different periods. Yugoslavian modernist architecture developed by domestic architects, influenced by modernist ideas from Central and Western Europe and with phenomenological support of the state can be considered as an indicator of social and cultural movements during the existence of that avant-garde socialist country from 1945-1990. Through the research of different study cases and examples of architecture from socialist Yugoslavia and studies of relevant scientists from the field of architecture and sociology, as a predominant methodology for this study, relations between architecture and socio-economic and cultural conditions will be investigated. In accordance with the declared ideas for general modernisation of the entire society, modernist architecture in Yugoslavia was widely accepted as a tool for the realisation of proclaimed ideals for open, human oriented and contemporary society. The architecture of cultural buildings was some of the best examples for the mentioned direction in the content, but even more in conceptual and visual expression. The Yugoslavian architecture of the representative cultural centres, museums, libraries and concert halls are some of the most successful realizations of modernism in the region of south east Europe, but even much wider. At the same time, these buildings were witnessing well organized, state supported institutional work that was able to arrange some of the most prominent cultural activities on the highest world level.