Basaltic Volcanic Rocks Research Articles

New details on the volcanic and tectonic evolution of the Mesoarchaean Dominion Group with special reference to the Syferfontein Formation in the Ottosdal area (South Africa)

Abstract The ca. 2.96 Ga Dominion Group (DG) preserves the first subaerial volcano-sedimentary succession on the Kaapvaal Craton. Based on field and core observations, this study provides revised stratigraphic logs and geological maps from the area around Ottosdal that refine the understanding of the stratigraphic and tectonic evolution of these ancient rocks. Fluvial sandstone and conglomerate of the Rhenosterspruit Formation (RsF) were deposited on granite basement, followed by andesitic to basaltic volcanic rocks of the Rhenosterhoek Formation (RhF). These amygdaloidal andesitic to basaltic lava units show fragmentation around lava flows that may represent an indication of prevalent subaerial environment. However, local hyaloclastite and pillow lava units indicate periodic aqueous conditions. The Syferfontein Formation (SF) has the most extensive exposures in the Ottosdal area and represents the youngest volcanic unit of the DG. The porphyritic and spherulitic volcanic rocks tell a story of subaerial volcanism interspersed with periods of lacustrine deposition of sandstone and shale. The Witwatersrand Supergroup (WSG) overlies the DG along an angular unconformity. Folding affected the succession of the DG, WSG and the Ventersdorp Supergroup (Rietgat Formation). This event is reflected in small-scale folds and mullion structures in the central part of the study area and by larger scale north-northwest–south-southeast-striking anticlines and synclines. Folding was accompanied by northwest-southeast-striking thrust faulting, either during or shortly after the formation of the Ventersdorp Supergroup. In the study area, post-Ventersdorp deformation is restricted to east-northeast–west-southwest-striking faults.

Water Projects in Ethiopia and their Implications for the Future of the Nile Water

Ethiopia is well known as the “East Africa water tower.” Water flows from it in all directions, north and west to the Nile River (Sudan and Egypt), And south to Lake Turkana (Kenya), Shabelle and Juba (Somalia). To the east, Lake Assal (Djibouti), Mountainous nature, and complex terrain dominate Ethiopia. Rainwater and its run-off mountain slopes and hills are the source of surface water for most Ethiopian lands. This paper discusses Ethiopia’s water situation, as the primary source country, which contributes about 85% of the Nile’s water, and discusses Ethiopia’s possibility to establish great dams. And the most important geological reasons behind the failure of many water projects in Ethiopia, whether on a large or small scale. Including the temporal and spatial diversity of rainfall, the high evaporation rate (87%), the different terrain, the severity of the slopes, the spread of weak basaltic volcanic rocks and fractured limestone, and a large number of faults and faults as a result of the seismic activity associated with the African trench, as well as the increase of the Ethiopian plateau. Alluvial sedimentation that negatively affects the storage capacity of dams.It also aims to assess the impact of existing or under-construction water projects on the water share of Egypt and Sudan and to identify future water projects in Ethiopia by analyzing previous data, reports, and scientific research, and finally finding ways to get out of the current crisis between countries The source on one side and the downstream countries (Egypt and Sudan) on the other side.

Late Permian rift-related volcanic rocks from the Zhongba Terrane, Southern Tibet: implications for the opening of the Neotethys

ABSTRACT The questions of how and when the Neotethys Ocean opened are crucial for understanding the evolution of the Tethys Realm and the break-up of Gondwana. However, the evolution of the Neotethys remains controversial. Herein, we report the zircon U–Pb ages, whole-rock major as well as trace elements, and Sr–Nd isotopic data for the basaltic volcanic rocks from the Zhongba Terrane in the western Yalung–Zangbo Suture Zone. The results demonstrate that the Saga basalts were extruded during the Late Permian (257–258 Ma). All samples are characterized based on the low SiO2 content (44.03–50.33 wt%) and belong to the high-K calc-alkaline series. Furthermore, they exhibit light rare earth element enrichment ((La/Yb)N = 12.7–26.7); slightly positive Eu anomaly(Eu/Eu* = 1.01–1.14); prominent Nb and Ta positive anomalies; slightly negative Zr, Hf, and Ti anomalies and exhibit high ratios of Ta/Hf (0.93–1.21), Zr/Y (8.68–10.63), and Nb/Zr (0.39–0.45). The (87Sr/86Sr)i ratio varied from 0.7050 to 0.7063, with relatively constant and depleted εNd(t) values ranging from 0.52 to 1.08. The rocks were probably sourced from a low-degree partial melting of the asthenospheric mantle in a rift environment and had undergone the process of fractional crystallization. These characteristics indicate that the Saga basalts differ from the rift-related magmatic rocks produced by the Panjal Traps. Consequently, combined with the recently reported detailed fieldwork, the Zhongba Terrane disintegrated from the northern margin of Gondwana during the Late Permian, promoting the opening of the Neotethys Ocean, which is most likely caused by the northward subduction of the Paleotethys Ocean.

The 1126 Ma volcanic event in the Dechang Area, SW Yangtze Block, and its significance

AbstractTraditionally, the strata of the Luonie Valley, Dechang County, SW Sichuan, China, are considered to contain a suite of felsic volcanic rocks (the Huili Group) that erupted after c. 1050 Ma. However, we report here new age constraints, elemental and Lu–Hf isotope geochemistry for a different suite of older basaltic agglomerate lava, basaltic tuff lava and basalt from the same area, which we name the Luonie Formation. New dating results show that the basaltic volcanic suite of the upper part of the Luonie Formation formed at 1126.1 ± 9.9 Ma, significantly earlier than deposition of the Huili Group, but comparable in age to the 1142 ± 16 Ma Laowushan Formation in central Yunnan Province. Granite intrusion into the Luonie Formation dated 1050.7 ± 12.7 Ma provides crucial supporting evidence for this earlier depositional age. We also report a maximum sedimentary age of c. 1158 Ma for the underlying arkose, implying stratigraphic conformity with the basaltic volcanic rock suite.The ϵHf(t) values of the basaltic volcanic rocks are mainly positive, indicating that the rocks are mainly derived from the depleted mantle and slightly stained by crustal materials. The characteristics of P*, Nb* and Zr* anomalies also support this view. The distribution patterns of trace and rare earth elements indicate that the basaltic volcanic rocks formed in an extensional setting. The Zr/4–Y–2Nb and Th–Nb/16–Zr/117 discrimination diagrams also provide evidence for this understanding. Lithofacies analysis shows that basaltic volcanic wrocks with the characteristics of both continental and marine facies should be formed in a littoral–neritic environment. We propose here that the evidence is consistent with a phase of continental extension that preceded the convergence of the SW Yangtze Block to form part of Rodinia.

Implication of Paleoproterozoic Basalt Fertility Related to Mantle Plume Activity in Nassara Gold Mineralization (Burkina Faso, West Africa)

The Birimian Nassara volcanic formations are located south of Gaoua in the southern part of the Boromo belt. Within these formations is the Nassara gold deposit where mineralization is hosted at the contact between basaltic volcanic rocks and sedimentary rocks. It is with the aim of understanding the geodynamic context of the basaltic rocks and the implication of their primary gold potential in the Nassara gold deposit that this work is carried out. To achieve our objectives, 28 samples of fresh basaltic rocks were geochemically analyzed for their major and trace element compositions. These analyses show that the Nassara basalts are Fe-rich tholeiitic basalts. Rare earth profiles (La/SmN = 0.75 - 1.50; La/YbN = 0.65 - 2.18) are fairly flat and without europium anomaly (Eu/Eu* = 0.90 - 1.09), nor niobium. In the Zr/Nb vs. Nb/Th and Nb/Y vs. Zr/Y binary diagrams, the Fe-rich tholeiitic basalts of Nassara, as well as those of the Houndé and Boromo belts, are placed in the field of oceanic plateau basalts related to a mantle plume system. A gold fertility test carried out on these basalts was positive. As other studies have already shown, the genetic link between gold deposits and mantle plumes appears to be a general rule. The scenario for the Nassara gold deposit is that it is the source magma that was already more or less enriched in gold and other related elements on its way up. The remobilization of this gold would have occurred during the Eburnean orogeny with the help of metamorphic, hydrothermal and deformation phenomena to be redeposited at the level of shear zones with economic grades. Through this analysis, we show that the fertility of the initial lithologies is very important for the formation of economic size deposits in the proximal shear zones. Exploration work should now integrate this dimension to define the best targets.

Central Hoggar groundwaters and the role of shear zones: 87Sr/86Sr, δ18O, δ2H and 14C isotopes, geochemistry and water-rock interactions

In an environment of volcanic and plutonic rocks such as the Central Hoggar, the knowledge of groundwater flows and their residence time is of prime importance. This is especially the case in the arid zone of Central Sahara where the main town of southernmost Algeria, Tamanrasset, with its rapidly growing population (>200,000 inhabitants extreme South of Algeria), put an important pressure on the local aquifers. Central Hoggar belongs to the LATEA metacraton, which is a Precambrian basement largely fractured and invaded by Cenozoic mostly basaltic volcanic rocks. In addition to superficial alluvial reservoirs, these two contrasted lithologies and large and deep faults determine the geometry of the aquifers and the nature and composition of water. We show here that distinct aquifers exist along faults oriented from NW-SE to NE-SW with no lateral communications. Some waters are in equilibrium with the Cenozoic volcanic system and others with the Precambrian basement although the latter bear often a Cenozoic volcanic signature attributed to volcanic coating along faults at depth. Alluvial, volcanic and Precambrian aquifers display contrasted measured pCO2 and specific conductivity (SC) values, stable (δ18O, δ2H), 87Sr/86Sr, 3H, δ13C and 14C isotopes. A major role is given to the Pan-African Adriane shear zone (ASZ), running just east of Tamanrasset, along which waters with high residence time (0.2<A14C < 45 pMC) are aligned in a 160–180 km long and 15 km wide corridor, including a natural soda spring (Tabahort). The latter have contrasted geochemical and isotopic signatures with respect to the other groundwaters originated from local evaporated precipitations. 87Sr/86Sr ratios vary from 0.70409 in volcanic aquifers to 0.72281 in Precambrian aquifers while C isotopes exhibit value from 0 to 117% pMC for 14C activity and δ13Cvalue from −12.5 to −2.12‰ vs VPDB. Trace elements are lower than the Maximum Admissible Concentration (MAC) except in the ASZ where Rb, Cs and U are found in higher concentrations elsewhere in Hoggar. This study enhances the peculiar status of the Central Hoggar groundwater aligned along the ASZ, close to the Tamanrasset City.

Geochronology and geochemistry of the South Scotia Ridge: Miocene island arc volcanism of the Scotia Sea

The ancestral South Sandwich arc (ASSA) records evidence of Oligocene – Miocene intra-oceanic island arc volcanism in the central Scotia Sea and potentially formed an important topographic barrier to deep ocean currents during the early development of the Antarctic Circumpolar Current. New geochemistry and geochronology of dredged basaltic samples from multiple sites across Discovery Bank, in the southern part of the ASSA, provide key information about this poorly understood volcanic arc in the Scotia Sea. Two new 40 Ar/ 39 Ar ages confirm volcanism was active in the Discovery Bank segment from 14 to 10 Ma, overlapping with the initial phase of spreading along the East Scotia Ridge. These ages are younger than previously determined for the ASSA and the island arc chain would have influenced deep ocean pathways in the southern Scotia Sea during the mid-Miocene. Geochemical analysis indicates that magmatism was derived from a depleted asthenospheric source, modified by subduction, akin to the present day South Sandwich island arc. Evidence from across Discovery Bank suggests that arc volcanism developed on pre-existing basaltic crust potentially related to Weddell Sea subduction, although the submerged bank is dominated by Miocene arc volcanic rocks. Evidence for an intra-oceanic island arc setting is also provided by the identification and imaging of a linear chain of rear-arc seamounts, characteristic of several volcanic centres in the present day South sandwich island arc. Mafic volcanic rocks, including ultramafic lithologies, from the neighbouring Bruce Bank topographic high have also been investigated and are demonstrated to have been generated in a different tectonic setting to the volcanic rocks of Discovery Bank. They are interpreted to be associated with the opening of Scan Basin during the Late Eocene, or potentially distal evidence of the gabbroic Pacific Margin Anomaly. • Discovery Bank forms part of an ancestral intra-oceanic island arc. • Basaltic volcanic rocks derived from a depleted mantle source. • Volcanism has been dated in the interval 14–10 Ma. • Volcanism on the ancestral arc overlaps with initial spreading on the East Scotia Ridge. • The arc volcanoes formed a barrier to deep ocean currents into the Late Miocene.

Convective-reactive transport of dissolved CO2 in fractured-geological formations

Carbon dioxide (CO2) storage in geologic formations is an attractive means of reducing greenhouse gas emissions. The main processes controlling the migration of CO2 in geological formations are related to convective mixing and geochemical reactions. The effects of heterogeneity on these coupled processes have been widely discussed in the literature. Recently, special attention has been devoted to fractured geological formations that can be found in several storage reservoirs. However, existing studies on the effect of fractures on the fate of CO2 neglect the key processes of geochemical reactions. This work aims at addressing this gap. Based on numerical simulations of a hypothetical reservoir, we explore the effect of fracture properties and topology on the domain's storage capacity at different rates of CO2 mineral dissolution. It is found that the fractures not only can help the mixing convection and reaction process in the domain but also may play a restrictive role in entering dissolved CO2 and hinder the plume fingers from growing. The hypothetical case is relevant in providing preliminary understanding but can show varying degrees of geological realism. For more representative geology, we investigate the migration-dissolution of buoyant CO2 on a large-scale outcrop of a volcanic basalt rock formation. The results show that neglecting thin fractures can significantly affect the predicted amount of trapped CO2. The storage capacity is more sensitive to heterogeneity at low dissolution rates. The findings are useful for the management of CO2 sequestration in fractured domains.

Geochemical and lead isotope compositions of olivine-hosted melt inclusions from the Yaeyama Graben in the southern Okinawa Trough: Implications for slab subduction and magmatic processes

Chemical compositions were measured in olivine-hosted melt inclusions in basaltic volcanic rocks from the Yaeyama Graben in the southern Okinawa Trough to investigate the magmatic processes of erupted lavas in an incipient epicontinental back-arc basin in the western Pacific. Melt inclusions have widely variable element and Pb isotope compositions, while erupted host whole-rock compositions are homogeneous, suggesting that melt inclusions preserve more information about magmatic processes than their host whole rocks. Two groups of melt inclusions can be distinguished by their trace elements and Pb isotopes. Group 1 melt inclusions have geochemical compositions similar to those of their host whole rocks, which have low 207Pb/206Pb ratios (<0.850), and may be attributed to the contributions of recycled continental crust and subducted sediments to magma sources during Philippine Sea Plate subduction. Group 2 melt inclusions have higher 207Pb/206Pb ratios (>0.850) and Li, Rb, and U contents and lower Cu, Zn, and Pb contents than their host whole rocks. High Li, Rb, and U contents may be induced by specific melts generated by possible breakdown reactions of some accessory minerals, such as phengite and cordierite, while low Cu, Zn, and Pb contents are attributed to sulfide precipitation, metal flushing and/or metallic element fractionation during magma evolution. The Pb isotopes of the group 2 melt inclusions are similar to those of the Kuanhsi-Chutung basalts, which are correlated with some intraplate volcanism in the Fujian-Taiwan region. We infer that the group 2 melts were preexisting small volumes of magma that were emplaced in the middle-lower continental crust (~11 km), experienced extensive magma evolution and were entrained by upwelling magma. Our melt inclusion data suggest that magma sources are compositionally heterogeneous and that the mixing of magmas from different sources may be widespread beneath the southern Okinawa Trough because of Philippine Sea Plate subduction and preexisting intraplate magmatism.

Evolution of lithospheric mantle beneath the Maguan region, southwestern margin of the South China block based on mantle xenoliths in Miocene alkaline volcanic rocks

The Maguan (MG) region in the southwestern part of the South China Block contains many Neogene potassic basaltic volcanic rocks along the Ailao Shan–Red River (ASRR) shear zone. These alkaline volcanic rocks contain abundant peridotite xenoliths which are mostly spinel (Spl)-facies lherzolite. We examined xenoliths in young, ~12 Ma, alkaline basalts. Most contain clinopyroxene (Cpx), >15 vol%, and minor xenoliths contain low Cpx, ~10 vol%. Olivine (Ol) shows forsterite components ranging from 88.6 to 90.1 in most lherzolite and from 90.4 to 90.8 in depleted lherzolite, Spl Cr# (=Cr/(Cr + Al)) between 0.08–0.11 for lherzolite and 0.17–0.22 for depleted lherzolite. Platinum group elements (PGE) show a near flat primitive mantle-normalized pattern; the ratios of IPGE/PPGE are 1.3–1.8 for lherzolite and 2.1 for depleted lherzolite. The xenoliths do not contain metasomatic minerals, but Cpx in depleted lherzolite samples is enriched in light rare earth elements (LREE; (La/Sm)N = 0.97–1.74). Two pyroxene geothermometry gives the temperatures ranging from 1029 °C to 1148 °C (average 1087 °C, n = 13). Spl–Ol geothermobarometry yields the oxidation state ranging from FMQ −1.5 to −0.25 with an average value of FMQ −0.59 (n = 13), which is comparable to those of abyssal peridotite and the asthenospheric mantle. The calculated temperatures and oxidation state are similar among samples independent of mineralogy and mineral chemistry, suggesting that partial melting and the cryptic metasomatism did not change the oxidation conditions. The data suggest that the subcontinental lithospheric mantle (SCLM) beneath the region formed from the asthenosphere mantle. Since the South China Block is generally underlain by Proterozoic SCLM, the data obtained this study suggest that the ancient lithosphere was replaced by the asthenospheric mantle in the local extension along the ASRR shear zone.

Geology, Geochemistry and Re-Os Age of the Qiaoxiahala Deposit in NW China: Evidence of an Overprinted Fe(-Cu/Au) Deposit

Overprinting of an earlier formed deposit may obscure the nature of the deposit and hinder our understanding of regional metallogeny. The Qiaoxiahala Fe(-Cu/Au) deposit in eastern Junggar, NW China, is characterized by magnetite mineralization later replaced by sulfide minerals such as chalcopyrite. To reveal the genesis of Qiaoxiahala, we conducted Re-Os dating on post-magnetite molybdenite separated from chalcopyrite and rare earth elements (REEs) for basaltic volcanic rock, magnetite, chalcopyrite and diorite. An isochron age of 377±7 Ma was obtained together with a weighted mean age of 375±3 Ma, which is indistinguishable from mineralization ages determined in previous studies. Rare earth element (REE) data for basaltic volcanic rocks hosting the ore are comparable to that of the magnetite, while the REE signatures of chalcopyrite from the Cu ore and local intrusive diorite share a similar pattern. These suggest that two distinct fluid sources are responsible for the deposition of Fe and Cu in the Qiaoxiahala deposit. According to these experimental results, we consider that the iron mineralization in Qiaoxiahala is the result of fluid exsolution from basaltic volcanism which was further overprinted by fluids that deposited copper and gold, which may have been sourced from nearby dioritic intrusions.

Studies of Concrete Mechanical Properties with Basalt Fibers

Current situation of construction industry demands competency in inventing new materials to enhance the mechanical properties of concrete in its strength point of view as well as durability. Basalt fibers are formed due to melting crushed volcanic basalt rock in a single stage phase. These are non-toxic and environmentally safe. Basalt fibers (BF) are highly resistant to heat, and possess insulating properties apart from having an elastic structure. In this context, the present study has been taken up to study the performance of concrete blended with basalt fibers and their influence on mechanical properties of concrete. The Basalt fibers of different proportions 0%, 0.1%, 0.3% and 0.5% in volume of concrete added to M40-grade concrete (BFRC)and tested for compressive strength, tensile strength and bending strengths. The results showed that concrete with 0.3% fibers exhibited maximum strength values.

Evidence from Late Cretaceous-Paleogene volcanic rocks of the Kyrenia Range, northern Cyprus for the northern, active continental margin of the Southern Neotethys

Late Cretaceous felsic and latest Cretaceous-Paleogene basaltic volcanic rocks are exposed throughout the Kyrenia Range, N Cyprus. Field mapping of the key, well-exposed western range indicates that the felsic volcanics mainly crop out in the southerly, frontal part of the range, separated from the latest Cretaceous-Paleogene basaltic volcanics farther north by a thrust. New U-Pb zircon dating of the felsic volcanics indicates a primary age of c. 74.0 Ma (Late Campanian). The felsic volcanics are characterised by evolved compositions that were probably generated in an extensional subduction-related setting. Their relatively low Nb and Y but high Rb concentrations, together with characteristic Th/Ta ratios (6–20), suggest a mature continental arc setting. The latest Cretaceous-Paleogene basaltic volcanics have mainly within-plate chemical characteristics (in the east), although some have a subordinate subduction influence; e.g. negative Nb (in the west). Sr-Nd-Hf isotopic signatures (i.e. high positive εNd(t) and εHf(t) values) suggest derivation of the basalts from several OIB-like mantle sources, with probable involvement of a crustal (recycled) component (i.e. elevated Nb/Y ratios). Comparisons with SE Turkey, where Late Cretaceous arc-related granitic rocks are widely developed, suggest that the Kyrenia Range igneous rocks may have originated to the south of the Alanya metamorphic massif (N of Cyprus) and correlative continental units in SE Turkey. The latest Cretaceous-Paleogene basaltic volcanics in N Cyprus and SE Turkey (Maden Complex) are interpreted to represent incipient marginal basin formation, possibly in an oblique-convergent setting, prior to Miocene suturing with Arabia. In the light of alternatives, we infer genesis of the N Cyprus Late Cretaceous and Paleogene volcanic rocks related to stages in the development of the northerly active continental margin of the Southern Neotethys.

Magnetic Signature of Serpentinization at Zedang in the South Tibetan Ophiolite Belt

AbstractMagnetic signature of serpentinized mantle peridotite has crucial importance in understanding the serpentinization process and interpreting the origin of strong magnetization anomalies at ultramafic‐hosted hydrothermal settings. However, different groups of serpentinized peridotites from both ocean drillings and ophiolite complexes have shown considerable variations in the abundance of magnetite (Oufi et al., 2002; Bonnemains et al., 2016; Li et al., 2017). We examined the magnetic properties, petrography and mineral chemistry of variably serpentinized peridotites from Zedang ophiolite in the eastern Yarlung‐Zangbo suture in south Tibet to evaluate the conditions of serpentinization and magnetite formation as well as magnetic sources in suture zones.The studied samples were 0–90% serpentinized with densities from 3.316 to 2.593 g cm–3 and show typical mesh textures of olivine replaced by serpentine on thin sections of core specimen. Serpentines were divided into type‐1 Fe‐poor serpentine mesh (1.84–2.88 wt% FeO) associated with magnetite in the early stage and type‐2 Fe‐rich serpentine cores (3.92–5.12 wt% FeO) with no formation of magnetite in the late serpentinization. Brucite vein appeared in central serpentine veins and show Mg/(Mg+Fe) values of 0.74–0.87 at ∼50–70% of serpentinization. Pure magnetite was identified as the main magnetic carrier by thermomagnetic analyses, but minor Cr‐magnetite (∼0.8 mole fractions of Fe3O4) was also detected due to oxidation of early spinel.All the peridotite samples show a rapid increase of magnetic susceptibility from ∼0.001 to ∼0.03 SI before 40–50% of serpentinization and a following flat trend in values 0.02–0.03 SI at &gt; 50% of serpentinization. This density–susceptibility relationship differs from the rapid production of magnetite above 60–70% of serpentinization for many abyssal peridotites (Oufi et al., 2002; Bach et al., 2006) and suggests that magnetite formation was coupled with hydration of olivine in the early serpentinization but the two decoupled at ∼ 40–50% of serpentinization. This transition is consistent with the petrographic observation that magnetite‐free serpentinization was developed in higher degrees (&gt; 50%) of serpentinization.Prior studies suggested that serpentinization of &lt; 200°C would generate Fe‐rich brucite, serpentine and little magnetite, whereas magnetite‐rich serpentinization was associated with Fe‐poor brucite and occurred at higher temperatures of 200–300°C (Klein et al., 2014). The petromagnetic features of serpentinized peridotites from the Zedang ophiolite indicate that the serpentinization process took place initially above 250°C (estimate from brucite composition) and continued to lower temperatures of &lt; 200°C, probably during the mantle lithosphere cooling down in forearc settings (Xiong et al., 2017). These serpentinized peridotites have higher magnetization intensities (average 2.26 Am–1) than mafic dolerite dykes and basaltic volcanic rocks (mostly &lt; 1 Am–1) and should be significant sources of aeromagnetic highs in the Yarlung‐Zangbo suture.

Concentración de la solución nutritiva y su relación con la producción y calidad de arándano azul

La producción, calidad y concentración nutrimental foliar del arándano azul (Vaccinium corymbosum L.) cv. Biloxi de bajo requerimiento de frío fue evaluada en cultivo hidropónico, empleando diferentes concentraciones de solución nutritiva. El ensayo se realizó en un invernadero tipo semitúnel, con cubierta de plástico, sistema de ventilación pasivo con apertura cenital y lateral, y sin control climático. Se emplearon plantas de arándano de un año de edad, provenientes de cultivo in vitro, y fueron colocadas en contenedores de plástico flexible de 15 L de capacidad con roca basáltica volcánica roja como sustrato, con un marco de plantación de 2 m entre hileras y 0,5 m entre plantas. El diseño experimental fue completamente al azar, con cuatro tratamientos y cinco repeticiones, y cada repetición tuvo cuatro plantas, lo que dio un total de ochenta plantas. Se evaluaron cuatro concentraciones de solución Steiner modificada (0,5; 1,0; 1,5 y 2,0 dS/m). Las variables evaluadas fueron producción y calidad de fruto, y se consideró tamaño, pH, sólidos solubles totales y firmeza, así como la concentración foliar de macronutrimentos en cada etapa fenológica. Se concluyó que el arándano azul cv. Biloxi es sensible a la salinidad del medio de crecimiento. Se determinó que, cuando el valor de conductividad eléctrica (CE) es mayor a 1,0 dS/m, afecta el crecimiento, producción y calidad del arándano; sin embargo, se puede utilizar una solución nutritiva con CE entre 0,5 y 1,0 dS/m sin afectar el rendimiento y la calidad de fruto, ni los niveles de concentración nutrimental foliar en cultivo hidropónico.

The age and geochemistry of the mid-Cretaceous volcanic rocks in the Jinan Basin: Implications for the mid-Cretaceous tectonic environments of the Korean Peninsula and Northeast Asia

Most of the mid to late Cretaceous igneous rocks in the southeastern margin of the Northeast Asian continent are interpreted to be formed due to upwelling of asthenospheric mantle caused by slab rollback and associated back-arc extension. However, the tectonic environments for the mid-Cretaceous igneous rocks in the Korean Peninsula is uncertain. The Jinan Basin is one of the Cretaceous pull-part basins in the southern Korean Peninsula. The mid-Cretaceous volcanic rocks occur in association with the Jinan Basin. In this study, we investigated whole-rock major and trace element geochemistry and Sr-Nd-Pb isotope compositions of the mid-Cretaceous volcanic rocks in the Jinan Basin to understand their petrogenesis and tectonic environments. Also, U-Pb zircon age of sedimentary and volcanic rocks in the Jinan Basin was determined to constrain the age of sedimentation and igneous activities. The results show that sedimentation started at least from 97.7 Ma and continued until 89.5 Ma. The sedimentary sequences were intermittently extruded by rhyolitic and andesitic magma 90–89 Ma, and later intruded by basaltic trachyandesite 84 Ma. The volcanic rocks in the Jinan Basin show geochemical features of alkaline to high-K calc-alkaline magma series with strong enrichment in large ion lithophile elements and light rare earth elements relative to high field strength elements. The mafic and intermediate volcanic rocks are distinguished from the typical continental arc magmas by enrichment in incompatible elements such as Y and Zr with high Zr/Y, suggesting that they originated from an enriched source. The basaltic trachyandesites and andesite have Sr isotope ratios (87Sr/86Sri) of 0.708769–0.709484 and Nd isotope ratios (143Nd/144Ndi) of 0.511782–0.511886, which indicate that they formed from mantle which was contaminated with crustal component in their petrogenesis. The Pb isotope data (206Pb/204Pb = 17.572–18.158, 207Pb/204Pb = 15.535–15.640 and 208Pb/204Pb = 38.366–38.921) suggest that the crustal component should have experienced a prolonged evolution with a low μ value. The Mg# (46–57) and Cr contents (40–180 ppm) in the mafic to intermediate rocks higher than typical crustal melts at a given range of SiO2, showing that they evolved from a mantle-derived primary magma. We attribute the crust-like geochemical and isotopic signature of the Jinan mafic and intermediate igneous rocks to the partial melting of enriched lithospheric mantle metasomatized by subduction components and subsequent crustal assimilation during magma ascent and pooling at the mid-crustal depth of ~9–10 km. The geochemical and isotopic features of the Jinan volcanic rocks are similar to those of the mid-Cretaceous basaltic volcanic rocks in the Yeongdong and Gyeongsang Basins, South Korea and the southeastern margin of South China Craton (SCC). This may suggest that the partial melting of the enriched lithospheric mantle, induced by slab rollback of the paleo-Pacific plate and upwelling of the asthenospheric mantle, was widespread underneath the southeastern Korean Peninsular as well as the southeastern margin of SCC.

Testing of Permian – Lower Triassic stratigraphic data in a half-graben/tilt-block system: evidence for the initial rifting phase in Antalya Nappes

Testing of Middle Permian – Lower Triassic stratigraphic data from the Antalya Nappes in a half-graben/tilt-block system has revealed the presence of episodic rifting events separated by periods of tectonic quiescence. Following a period of uplift during the Permian (Late Artinskian to Roadian), the basement rocks have been activated by displacement faults and several depocenters in half-graben-like asymmetrical basins began to be filled with Roadian to Wordian continental clastic deposits intercalated with coal and marine rocks. The Early Capitanian time was a period of tectonic quiescence. The second event occurred in Middle to Late Capitanian times and produced basaltic volcanic rocks intercalated in the shallow marine fossiliferous carbonate successions. Following the Lopingian (Wuchiapingian and Changhsingian) and Permian–Triassic boundary interval representing a long tectonic quiescence, the last rifting episode started with an abrupt facies change in the late Griesbachian. Variegated shales, limestones, volcanics, talus breccia, and debris flow deposits were laid down in a half-graben/tilt-block system. As normal faulting has become active, the deposition continued on the subsiding hanging wall side. The stratigraphic gap increased in magnitude as the erosional truncation has incised deeply the footwall side. This initial rifting phase in the Antalya Nappes is prior to the onset of a stronger and more continuous rifting event that occurred in the Anisian–Carnian interval including a variety of deepwater clastic and carbonate deposits, radiolarites containing sometimes blocks and clasts derived from the basin margins, and volcanic rocks carrying intraoceanic setting character.

Structural analysis and dielectric relaxation mechanism of conducting polymer/volcanic basalt rock composites

Abstract In this work, polypyrrole and polythiophene conducting polymers (CPs) have been synthesized and doped with volcanic basalt rock (VBR) in order to improve their dielectric properties for technological applications. The structure and morphology of the composites with different VBR doping concentrations were characterized by FT-IR and SEM analyses. The best charge storage ability was achieved for maximum VBR doping concentration (50.0 wt.%) for both CPs. Dielectric relaxation types of the composites were determined as non-Debye type due to non-zero absorption coefficient and observation of semicircles whose centers were below Z′ axis at the Nyquist plots. It was also ascertained that VBR doping makes the molecular orientation easier than for non-doped samples and reduced energy requirement of molecular orientation. In addition, AC conductivity was totally masked by DC conductivity for all samples at low frequency.

Pacific Lithosphere Evolution Inferred from Aitutaki Mantle Xenoliths

Abstract Highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, Re), major and trace element abundances, and 187Re–187Os systematics are reported for xenoliths and lavas from Aitutaki (Cook Islands), to investigate the composition of Pacific lithosphere. The xenolith suite comprises spinel-bearing lherzolites, dunite, and harzburgite, along with olivine websterite and pyroxenite. The xenoliths are hosted within nephelinite and alkali basalt volcanic rocks (187Os/188Os ∼0·1363 ± 13; 2SD; ΣHSE = 3–4 ppb). The volcanic host rocks are low-degree (2–5%) partial melts from the garnet stability field and an enriched mantle (EM) source. Pyroxenites have similar HSE abundances and Os isotope compositions (Al2O3 = 5·7–8·3 wt %; ΣHSE = 2–4 ppb; 187Os/187Os = 0·1263–0·1469) to the lavas. The pyroxenite and olivine websterite xenoliths directly formed from—or experienced extensive melt–rock interaction with—melts similar in composition to the volcanic rocks that host the xenoliths. Conversely, the Aitutaki lherzolites, harzburgites and dunites are similar in composition to abyssal peridotites with respect to their 187Os/188Os ratios (0·1264 ± 82), total HSE abundances (ΣHSE = 8–28 ppb) and major element abundances, forsterite contents (Fo89·9±1·2), and estimated extents of melt depletion (&amp;lt;10 to &amp;gt;15%). These peridotites are interpreted to sample relatively shallow Pacific mantle lithosphere that experienced limited melt–rock reaction and melting during ridge processes at ∼90 Ma. A survey of maximum time of rhenium depletion ages of Pacific mantle lithosphere from the Cook (Aitutaki ∼1·5 Ga), Austral (Tubuai’i ∼1·8 Ga), Samoan (Savai’i ∼1·5 Ga) and Hawaiian (Oa’hu ∼2 Ga) island groups shows that Mesoproterozoic to Neoproterozoic depletion ages are preserved in the xenolith suites. The variable timing and extent of mantle depletion preserved by the peridotites is, in some instances, superimposed by extensive and recent melt depletion as well as melt refertilization. Collectively, Pacific Ocean island mantle xenolith suites have similar distributions and variations of 187Os/188Os and HSE abundances to global abyssal peridotites. These observations indicate that Pacific mantle lithosphere is typical of oceanic lithosphere in general, and that this lithosphere is composed of peridotites that have experienced both recent melt depletion at ridges and prior and sometimes extensive melt depletion across several Wilson cycles spanning periods in excess of two billion years.

Does the metavolcanic-sedimentary Rio do Coco Group, Araguaia Belt, Brazil, represent a continuity of the Quatipuru ophiolitic complex? – Constraints from U-Pb and Sm-Nd isotope data

Serpentinized peridotites and basaltic volcanic rocks from the Quatipuru, Serra do Tapa, and Morro do Agostinho complexes are part of dismembered ophiolite bodies hosted by metasedimentary units of the Neoproterozoic Araguaia Belt, Tocantins Province, central Brazil. Approximately 10 lenticular ultramafic bodies, which contain primitive (serpentinite) and more evolved (actinolite schist, actinolite-talc schist, actinolite-serpentinite schist, talc schist, talc-serpentine schist, actinolitite, cloritite) rocks, were identified in the Rio do Coco Group (RCG), a metavolcanic-sedimentary sequence in the southern portion of the belt. These bodies are intercalated with metasedimentary rocks. All lithologies are metamorphosed to upper greenschist and lower amphibolite facies. The sequence was initially characterized as a classic Archean greenstone belt, but the present study suggests that it should be considered an ophiolite suite. On the basis of the ƐNd(t) values the RCG rocks can be subdivided into two groups: Group 1, with positive ƐNd(t) values, neodymium model ages (TDM) of ca. 1.0 to 1.1 Ga, with ocean-island-basalt (OIB) affinity, and being less contaminated with metasedimentary rocks of the Baixo Araguaia Supergroup; and Group 2, with negative ƐNd(t) values, TDM ranging from 1.2 to 1.7 Ga, with a variable ocean island basalt (OIB), plume or enriched mid-ocean-ridge basalt (P- and E-MORB) affinity, and being more contaminated with metasedimentary rocks. Two samples were analyzed by the U-Pb method on zircon (LA-MC-ICPMS). The weighted average age from a serpentinite (715 ± 26 Ma) and an actinolite schist (702 ± 24) indicates a maximum emplacement age for this sequence at 708 ± 35 Ma, which is similar to the previously published age for the Quatipuru Complex (Sm-Nd isochron age of 757 ± 49 Ma). This may suggest that the metavolcanic-sedimentary sequence of the Rio do Coco Group and the Quatipuru ophiolite system could be part of the same dismembered oceanic lithosphere.