Granite Pebbles Research Articles

Operating performance of a Joule-Brayton pumped thermal energy storage system integrated with a concentrated solar power plant

The expected performance of an innovative Pumped Thermal Energy Storage (PTES) system based on a closed-loop Brayton-Joule cycle and integrated with a Concentrated Solar Power (CSP) plant are analysed in this study. The integrated PTES–CSP plant includes five machines (two compressors and three turbines), a central receiver tower system, three water coolers and three Thermal Energy Storage (TES) tanks, while argon and granite pebbles are chosen as working fluid and storage media, respectively. A sizing of the main components of the integrated plant has been firstly carried out for the design of an integrated PTES-CSP plant with a nominal net power of 5 MW and a nominal storage capacity of 6 equivalent hours of operation. Specific mathematical models have been developed in MATLAB-Simulink to simulate the PTES and CSP subsystem in different operating conditions, and to evaluate the thermocline profile evolution within the three storage tanks during/charging and discharging processes. A control strategy has finally been developed to determine the operating modes of the plant based on the grid service request, the solar availability, and the TES levels. The performance of the system during a summer and a winter day have been analysed considering the integration of the PTES subsystem in the Italian energy market for arbitrage. Results have demonstrated the technical feasibility of the hybridization of a PTES system with a CSP plant and the ability of the integrated system to participate to energy arbitrage, although a lower exergy roundtrip efficiency (about 54 %) has been observed with respect to the sole PTES system (about 60 %).

Widespread Cadomian–Pan-African Ediacaran magmatism across the Moroccan Meseta: Implication for the geodynamic evolution of the NW Gondwana margin

The Moroccan Meseta constitutes a key peri-Gondwanan and Variscan terranes linking the branches between the SW European Cadomian and the north West African Craton (WAC), anti-Atlas metacratonic Pan-African terranes. While the Paleozoic sedimentary and tectono-magmatic record of the different blocks of the Moroccan Meseta is well documented, there is still a lack of systematic absolute ages and geochemical isotopic data of putative Precambrian basement rocks from different Meseta blocks. Here we present new U–Pb zircon ages, petrological, and whole-rock major, trace, and Sr–Nd–Pb isotope geochemical data of (meta)igneous rocks from the Bou-Acila, Jbel-Hadid, Goaïda, Midelt and El Jadida, constituting the basement of two main Moroccan Meseta blocks. Basaltic rocks, unconformably overlain by Cambrian platform sediments, in the Western Meseta Bou-Acila basement yield U–Pb zircon age of c. 581 ± 9 Ma that unveils the existence of Ediacaran magmatism in the Moroccan basement of this area. Alleged early Paleozoic mafic sills in the metasedimentary series of the Midelt Sidi-Saïd yield U–Pb zircon ages of c. 554 ± 12 Ma reveals, for the first time, the presence of Ediacaran magmatism in the basement of the Moroccan Eastern Meseta. U–Pb zircon ages in the Jbel-Hadid and El Jadida rhyolitic basement rocks (c. 604–543 Ma and c. 575–559 Ma, respectively), as well as granitic pebbles (c. 573 Ma) in the Goaïda Cambrian limestone series, further attest for coeval Ediacaran magmatism in the basement of Western Meseta. The geochemical affinity of the investigated Moroccan Meseta Ediacaran magmatic rocks is mainly metaluminous, low-K tholeiites for mafic rocks, and peraluminous, high-K calc-alkaline for the felsic rocks, consistent with a back-arc tectonic setting. Geochemical and Sr–Nd–Pb isotopic data indicate that the source of the Moroccan Meseta Ediacaran magmatism involved sources from the depleted mantle and old WAC crustal basement. Altogether, these data show widespread Ediacaran magmatism in the Moroccan Meseta mostly likely formed in a back-arc south of the Cadomian active margin along the NW Gondwana during the waning stages of the Cadomian–Pan-African orogeny, recording a transitional stage between the Ediacaran subduction and early Paleozoic rifting.

Preliminary progress report on 10Be and 26Al sample preparation at the IHEG, CAGS AMS laboratory

Based on previous experimental methods, this study explored the separation of quartz from other minerals and an extraction protocol for 10Be and 26Al. The results showed that paramagnetic minerals are removed with current multistage physical and chemical purification process. A dowex 50 W × 8 (H+) ion-exchange resin column was used for 10Be and 26Al chromatography. The optimal elution fractions for separating Be using 1.1 M HCl were 40–140 ml with a recovery rate of 83 % and those for separating Al using 6 M HCl were 170–230 ml with a recovery rate of only 33 %. The blank values of 10Be/9Be and 26Al/27Al ratios were 4.59E−15 and 2.49E−14, respectively. Two granite pebbles samples were analyzed using the experimental procedure established in this study, and the 10Be/9Be and 26Al/27Al ratios were (4.72 ± 0.23)E−13, (2.99 ± 0.22)E−13, and (7.28 ± 0.40)E−13, (2.83 ± 0.29)E−13, respectively.

Permian A-type granites of the Western Carpathians and Transdanubian regions: products of the Pangea supercontinent breakup

Permian biotite leucogranites to granite porphyries and rhyolites form small intrusions in several Alpine tectonic units in the Western Carpathians and the Pannonian region (Slovakia and Hungary). Their A-type signature is inferred from main- and trace-element geochemistry, with high K, Rb, Y, REE, Zr, Th, Nb, Fe/Mg and Ga/Al, low Al, Mg, Ca, P, Sr, V and strong negative Eu-anomaly. This geochemical signature is further supported by the mineralogy comprising local hypersolvus alkali feldspars, annitic biotite and the presence and composition of HFSE accessory minerals. The δ18O values measured for zircon (mean value 8.3 ‰ ± 0.36) may be explained by the melting of igneous material of crustal origin and/or mantle basalts which interacted with low-temperature fluids. The in-situ SHRIMP U–Pb isotope dating of zircon from the granites highlights two different periods of magmatic crystallisation and pluton emplacement: the older 281 ± 3 Ma Cisuralian age in the southern part, Velence Hills in the Pannonian region (Transdanubian Unit) and younger Guadalupian ages in the northern part, the West-Carpathian area: 262 ± 4 Ma (Turčok, Gemeric Unit), 267 ± 2 Ma (Hrončok, Veporic Unit) and 264 ± 3 Ma (Upohlav, granitic pebbles in Cretaceous conglomerates of the Pieniny Klippen Belt). The ~ 280 to 260-Ma interval is simultaneous with post-orogenic or anorogenic, rift-related and mainly alkaline (A-type) magmatism on the broader European scale. Our study documents a close relationship between the Permian continental rifting and the Neotethyan Meliatic oceanic basin opening in the Middle Triassic. The A-type granites originated from the partial melting of the ancient lower crustal quartzo-feldspatic rocks with the possible contribution of meta-basic material from the mantle in an extensional tectonic regime consistent with disintegration of the Pangea supercontinent during the Permian–Triassic period.

The Late Triassic Molasse Deposits in Central Jilin Province, NE China: Constraints on the Paleo-Asian Ocean Closure

This paper presents a new detailed study including zircon U-Pb-Hf isotopic, whole-rock geochemical and Sr-Nd isotopic analyses of conglomerate and granitic pebbles from the molasse deposits in central Jilin Province, NE China. These data are used to better constrain the Late Permian–Triassic tectonic evolution regarding particularly the final closure of the Paleo-Asian Ocean (PAO) along the Changhun-Yanji suture (CYS). Zircon U-Pb data indicate that the granitic pebbles formed in the end-Permian (254–253 Ma). The youngest detrital zircon age of 231 Ma from the conglomerate, and presence of the overlying Upper Triassic Sihetun Formation suggests that the molasse deposits on the Jin′gui Island formed during the Late Triassic. The end-Permian granitic rocks display high SiO2 (66.07–74.77 wt %), with low MgO (0.55–2.05 wt %) and Mg# (31.61–43.64) values, together with depleted Hf and Nd isotopic values (εHf(t) = +1.61 to +11.62; εNd(t) = +3.3 to +4.2; (87Sr/86Sr)i = 0.706458–0.706842) and juvenile second-stage Hf model ages (1148–512 Ma), suggesting that they were probably generated by the partial melting of a Meso-Neoproterozoic juvenile metabasaltic lower crust. They are characterized by enrichments in large ion lithophile elements (LILEs) and depletions in high field strength elements (HFSEs), with affinities to igneous rocks forming in a subduction-related setting. This, combined with regional coeval subduction-related magmatic rocks, indicates that the PAO still existed along the CYS. In addition, the identification of Late Triassic molasse deposits on the Jin′gui Island in this study, coupled with occurrences of many Early Triassic syn-collisional granitoids along the CYS, indicates that the final closure of the PAO took place prior to the Late Triassic.

U–Pb isotopic ages and provenance of some far-travelled exotic pebbles from glaciogenic sediments of the Polonez Cove Formation (Oligocene, King George Island)

Zircon grains from nine erratic pebbles of granite, granodiorite–tonalite and quartzite from the Polonez Cove Formation (southern King George Island) were studied for their U–Pb isotope ages and provenance. The calculated concordia ages of the studied pebbles are 108.79 ± 0.89, 119.7 ± 2.2, 178.6 ± 2.8, 180.7 ± 1.9, 207.4 ± 3.1, 231.1 ± 1.9, 1087.5 ± 4 and 1833 ± 4 Ma. The source area of individual pebbles was analysed and defined. Pebbles of crystalline rocks were derived from the Antarctic Peninsula, as well as from the Antarctic mainland. The erratic made of quartzite was eroded from the southernmost part of the Ellsworth Mountains (Linder Peak Member of Howard Nunatak Formation). Our isotope data analytically support the earlier thesis that the Oligocene ice-sheet covered a substantial part of Antarctica and its nucleus was located in its central part. Supplementary material: The U–Pb isotope data (Table S1) are available at https://doi.org/10.6084/m9.figshare.c.5233335

Provenance of upper Permian-lowermost Triassic sandstones, Wutonggou low-order cycle, Bogda Mountains, NW China: implications on the unroofing history of the Eastern North Tianshan Suture

This study investigates the provenance of sedimentary rocks in Bogda Mountains, NW China, and reconstructs the lithology and unroofing history of the Eastern North Tianshan Suture. Petrographic point counting data of sandstones and compositions of conglomerates of upper Permian-lowermost Triassic Wutonggou low-order cycle from Zhaobishan, North Tarlong, Taodonggou, and Dalongkou sections in the southern and northern foothills of Bogda Mountains were used to interpret the temporal and spatial variations of lithology of the Eastern North Tianshan Suture, which is the sediment source area. Three compositional trends were identified. A trend of upward-increasing quartz content and granitic pebbles in Zhaobishan section suggests a change from the undissected volcanic arc, accretionary wedge and trench setting to predominantly transitional volcanic arc and subordinate accretionary wedge and trench, in the eastern part of the Eastern North Tianshan Suture. In North Tarlong and Taodonggou sections, however, the lithic content decreases and the contents of quartz and granitic pebbles increase up sections. These trends indicate that the western part of the Eastern North Tianshan Suture changed from an undissected volcanic arc to the transitional volcanic arc, accretionary wedge and trench. No clear trend in the lithic-rich sandstones of the Dalongkou section indicates that sediments were derived from the undissected volcanic arc in the Eastern North Tianshan Suture and local rift shoulders. Compositional variations of studied rocks suggest that the Eastern North Tianshan Suture was an amalgamated complex with great spatial and temporal heterogeneities in lithology and experienced persistent unroofing during late Permian-earliest Triassic. This study reconstructs a key element of the Chinese Tianshan Suture and serves as an example to understand the unroofing processes of ancient sutures.

Experimental Investigation on PCC for Workability within Partial Replacement of M-Sand by Ecosand

In whole nation, concrete production events are enchanting abode on vast scale. Natural sand (river sand) is unique of the main requirements of concrete and it is pretty demand and exclusive. Manufactured sand (M-sand) is a standby of river sand for concrete assembly which is produced from rigid granite pebble by devastating. Eco-sand is fine particles which is outgrowth from cement trade. Effective use of this waste material should be done for cost efficiency. The present study is about the compressive strength of concrete block with limited surrogating of M-sand by Eco-sand. The conventional river sand is replaced with M sand and partial amount of silica sand Replacement of M-sand by Eco-sand at various percentages 0%, 6%, 12% 18%, 24%&30% in PCC.It is verified that the finest spare percentage of M-sand by Eco-sand and the properties of fresh concrete and hard concrete in PCC with eco-sand. The comparison of economic advantages of m sand and eco sand. The main objective of this project is to reduce the air pollution and eco-friendly. The various proportions is carried out and tested.

Experimental analyses of sensible heat thermal energy storage systems during discharging

The discharging performance of a sunflower oil TES tank is compared with two sunflower oil/rock-bed TES tanks with two different granite rock pebble sizes. The average particle diameters of the rock pebbles are 10.5 mm and 31.9 mm respectively, with respective void fractions of 0.39 and 0.43 in the TES tanks. The TES systems were initially charged before the commencement of the discharging experiments. The temperature profiles, energy rates, exergy rates, exergy recovery efficiency and stratification number profiles are evaluated during discharging cycles at flow rates of 4 mls−1, 8 mls−1 and 12 mls−1, respectively. The results obtained show that the discharging times, discharging energy rate, exergy rates, exergy recovery efficiency and the TES tanks’ de-stratification characteristics were all dependent on the HTF flow rates. The big pebbles have greater exergy rates than the small pebbles at 4 mls−1. The discharging energy rates and discharging exergy rates of the small pebbles are greater at the higher flow rates of 8 mls−1 and 12 mls−1 due to its larger thermal energy content. The TES tanks showed better stratification with the lowest flow rate of 4 mls−1 than at the higher flow rates. The increase in de-stratification is due to the faster thermal mixing effect at the higher flow rates. The small pebbles TES experiences the greatest thermal de-stratification followed by the oil-only TES and finally by the big pebbles TES at the higher flow rates (8 mls−1 and 12 mls−1). The greatest thermal exergy recovery was obtained with the TES tank filled with the large granite pebbles and at all the flow rates. Lower heat losses therefore, occur from the TES with the larger granite pebbles to the environment when compared to the other storage tanks. The greatest losses occurred with the oil-only TES system. The results show that the discharging performance of the oil-only TES was enhanced by the addition of the granite pebble bed particularly with the pebbles of average size of 31.9 mm.

Bioleaching of arsenopyrite from Janggun mine tailings (South Korea) using an adapted mixed mesophilic culture

This article explores a heap bioleaching technology for the removal of arsenic (As) from mine tailings using the GEOCOAT™ technique. Small-scale columns were operated at fixed temperatures of 20 °C, 30 °C, and 45 °C and at ramped-up temperatures from 25 °C to 45 °C using a mixed mesophilic acidophilic iron and sulfur oxidizing microbial culture, adapted to high As concentration (20 g/L). The packed-bed columns were filled with inert granite pebbles coated with Janggun Mine tailings, irrigated with a 1 g/L ferrous-enriched 0 K medium and aerated with 200 mL/min compressed air. To study the microbial colonization at various stages of the leaching process relative to the initial inoculum, the ramped-up-temperature experiment was conducted in triplicate and the columns were sacrificed after different leaching periods. The fixed-temperature column samples were sampled upon the termination of each experiment, for microbial speciation of the culture attached to the mineral during the leaching of the ore. The As that was released into the solution, the iron oxidation rates, the pH and the redox potential were used to assess the leaching performance of each column. A triangulation of the results between the fixed and the ramped-up temperatures allowed determination of the influence of temperature on As leaching kinetics and microbial distribution. 94–97% As removal was achieved among the various column experiments, 88 days after inoculation. The results showed that increased temperature induced an increased lag in the As leaching phase. Temperature also affected the abundance of acidophilic microorganisms present in the combined bulk volume of the column and on the mine tailings. The mesophilic bacterial species Acidithiobacillus caldus and Leptospirillum ferriphilum were the dominant biooxidation species (> 60%) in both the inoculum applied to the columns and in Col. A operated at a fixed 20 °C. Increased incubation temperature resulted in a decrease in the number of bacterial cells; however, the number of archaeal cells remained similar with a resulting increase in the archaeal dominance at 45 °C. The ramped-up temperature study showed similar results with an increase in both cell numbers and archaeal dominance between day 42 and 84. Overall, this study demonstrated the feasibility of As detoxification from the Janggun Mine tailings using microbial heap leaching.

Cryptic climatic signatures and tectonic controls on Cryogenian diamictites in the NW Tarim Craton, China

Unravelling the origins of Cryogenian diamictites is vital in determining their significance in a snowball Earth context and their relationship to environmental processes. Here, we present new sedimentological and geochemical data for the Cryogenian sedimentary rocks from the Tarim Craton, NW China. The diamictite member of the East Qiaoenbrak Formation contains (1) granitic pebbles with high sphericity, (2) well-developed stratification and (3) bed-scale grain-size changes suggesting cyclicity; also, (4) ice-rafted debris is conspicuously absent. Rather than deposits of direct glacial origin, the succession is instead interpreted as a subaqueous fan complex. The major and trace element ratios and REE patterns are consistent throughout 22 sampled intervals in the Qiaoenbrak Group, suggesting a uniformly felsic source area, probably from an island arc. Chemical index of alteration (CIA) analysis indicates low CIA values (49.5–54.3, average 51.6) throughout the Qiaoenbrak Group. We suggest that both the Qiaoenbrak Group and Yuermeinak Formation were deposited during the Marinoan glaciation, in a long-lasting cold and dry interval. It is likely that the Qiaoenbrak Group was deposited in a fault-controlled basin adjacent to an active continental margin, although the material may ultimately have derived from a glacial source (e.g. outwash).

Early Permian age of granite pebbles from an Eocene or Oligocene conglomerate of the Internal Rif belt (Alboran domain, Morocco): hypothesis on their origin

Granite pebbles from an Eocene or Oligocene conglomerate lying on a Ghomaride nappe of the Internal Zones of the Rif belt (Alboran domain, Morocco) have been dated by U/Pb on zircon at 281 Ma. No granite pluton being known in the Rif belt nor in the neighbouring Betic Cordillera, the origin of these calc-alkaline Kungurian (end of the Early Permian) granites is discussed. A provenance from a nearby unit presently drowned in the Alboran sea is likely. Comparisons with other circum-Mediterranean domains show that this late plutonism characterizes an original domain in the Variscan orogen.

Nd, Pb, Hf isotope characteristics and provenance of glacial granitic pebbles from Late Ordovician diamictites in the Taurides, S Turkey

Outcrops of the Late Ordovician glacio-marine deposits in Tauride Anatolide Platform contain rare rounded/sub-rounded glacially transported granitic pebbles. Recently determined crystallization ages of the granitic fragments by LA-ICP-MS U-Pb zircon dating fall in two groups, 575 to 600Ma and 700 to 965Ma. Crystallization ages are in the range of juvenile magmatic rocks in the Arabian Nubian Shield except one sample implying pre-0.87Ga magmatic activity. All dated granitic pebbles geochemically show arc-related compositions and juvenile isotopic systematics (whole rock ƐNd(T), Pb-Pb and zircon ƐHf(T) isotopic data). Marginal arc type sources fit well with the geochemical and isotopic data of the granitic pebbles of 700 and 800Ma that have juvenile Hf-TDM and older Nd-TCR modal ages. However, A-type affinity of three samples, ranging from 575 to 600Ma show that they might have been derived from mixing of juvenile mantle and older crustal sources having older Hf-TDM and Nd-TCR modal ages. A 965Ma granitic fragment has the oldest Hf-TDM and Nd-TCR model age(s) implying involvement of pre-Neoproterozoic crustal source(s) in its genesis. These results collectively suggest that the glacio-marine successions in the Tauride Anatolide Platform were eroded from Neoproterozoic granitic/meta-granitic/meta-granodioritic rocks in the northern Nubian Shield (Egypt) and were then transported to the Tauride-Anatolide Platform by the glacial sheets during Late Ordovician time.

Composition and geodynamic setting of Late Paleozoic magmatism of Chukotka

The paper reports the results of petrogeochemical and isotope (Sr-Nd-Pb-Hf) study of the Late Paleozoic granitoids of the Anyui–Chukotka fold system by the example of the Kibera and Kuekvun massifs. The age of the granitoids from these massifs and granite pebble from conglomerates at the base of the overlying Lower Carboniferous rocks is within 351–363 Ma (U-Pb, TIMS, SIMS, LA-MC-ICP-MS, zircon) (Katkov et al., 2013; Luchitskaya et al., 2015; Lane et al., 2015) and corresponds to the time of tectonic events of the Ellesmere orogeny in the Arctic region. It is shown that the granitoids of both the massifs and granite pebble are ascribed to the I-type granite, including their highly differentiated varieties. Sr-Nd-Pb-Hf isotope compositions of the granitoids indicate a contribution of both mantle and crustal sources in the formation of their parental melts. The granitic rocks of the Kibera and Kuekvun massifs were likely formed in an Andean-type continental margin setting, which is consistent with the inferred presence of the Late Devonian–Early Carboniferous marginal-continental magmatic arc on the southern Arctida margin (Natal’in et al., 1999). Isotope data on these rocks also support the idea that the granitoid magmatism was formed in a continental margin setting, when melts derived by a suprasubduction wedge melting interacted with continental crust.

Investigating the Bioleaching of an Arsenic Mine Tailing Using a Mixed Mesophilic Culture

The aim of this study was to investigate the microbial colonization and arsenic leaching kinetics of South Korean mine tailings containing arsenopyrite at fixed temperatures (20°C, 30°C and 45°C) and at ramped up temperatures (25 to 45°C, with a 2°C daily increase). The experiments were conducted in a packed bed of inert granite pebbles coated with the tailings material and leached with a mesophilic culture dominated by Acidithiobacillus caldus (56%), a lesser percentage of Leptospirillum ferriphilum (29%) and Archaea (15%), using 1 g/L ferrous-enriched 0K medium. The ramped-up temperature experiment was conducted in triplicate and columns were sacrificed after different leach periods to study the evolution of microbial species dominating the colonization. The leaching performance was evaluated using the arsenic released into solution, the iron oxidation rates, the pH and the redox potential. The microbial speciation of the culture attached to the solids during the leach experiment was determined upon completion of each experiment. A steady arsenic solubilisation of between 94 and 97% was observed among the various column experiment after 88 days post inoculation. Microbial speciation performed following the leaching of the mineral indicated a shift of microbial communities in the columns when compared to the initial inoculum.

Laser Ablation Inductively Coupled Plasma Mass Spectrometry U-Pb Dating of Detrital and Magmatic Zircons of Glacial Diamictites and Pebbles in Late Ordovician Sediments of the Taurides and Southeast Anatolian Autochthon Belt, Turkey: Indications for Their Arabian-Nubian Provenance

Late Ordovician (Hirnantian) glacio-marine deposits in the Central and Eastern Taurides and Southeast Anatolian Autochthon Belt (SAAB) in Turkey are mainly composed of diamictites, subrounded granitic pebbles, and rounded/subrounded lonestone pebbles. The granitic pebbles are dated as 576.5 ± 3.3, 576.7 ± 5.7, 598.4 ± 7.5, 717.5 ± 8.0, 789.5 ± 3.7, and 964.6 ± 4.6 Ma. The geochemical signatures and dated granitic pebbles in the Central and Eastern Taurides are interpreted to have been derived from the Late Neoproterozoic granitoids/metagranitic rocks of the Arabian-Nubian Shield (ANS; the Sinai Peninsula and the Eastern Desert of Egypt). The youngest 206Pb/238U ages in the diamictites (499.1 ± 4.2 Ma in the SAAB, 530.5 ± 5.3 Ma in the Eastern Taurides, and 562.5 ± 5.4 Ma in the Central Taurides) and in the lonestones (528.2 ± 4.5 Ma in the Central Taurides, 530.8 ± 5.2 Ma in the Eastern Taurides) indicate that detrital zircons were directly transported mainly from the northern margin of Gondwana and/or Arabia during the Late Ordovician, not from peri-Gondwanan parts of the European margin. Kernel/probability density diagrams of zircon ages from the lonestone pebbles in the Eastern and Central Taurides are interpreted as evidence for their derivation from Late/Middle Cambrian siliciclastic rocks in the Israeli part of the Sinai Peninsula. The provenance of detrital zircon populations in the diamictites in the Central and Eastern Taurides is directly correlated with magmatic activity of the Elat (Taba)–Feiran island arc, the Sa’al island arc, and the postcollisional magmatic suites in the Sinai Peninsula (Egypt). However, the corresponding successions in the SAAB have more abundant Late Cryogenian age components, suggesting the Ha’il/Afif/Ad Dawadimi/Ar-Rayn terranes of the eastern Arabian Shield as their provenance. These distinctive age patterns indicate that glacio-marine successions in the SAAB had different paleogeographic positions than their equivalent units in the Central and Eastern Taurides during deposition of the Late Ordovician glacio-marine units.

Evidence for multi-cycle sedimentation and provenance constraints from detrital zircon U–Pb ages: Triassic strata of the Lusitanian basin (western Iberia)

Laser ablation ICP-MS U–Pb analyses were conducted on detrital zircons of Triassic sandstone and conglomerate from the Lusitanian basin in order to: i) document the age spectra of detrital zircon; ii) compare U–Pb detrital zircon ages with previous published data obtained from Upper Carboniferous, Ordovician, Cambrian and Ediacaran sedimentary rocks of the pre-Mesozoic basement of western Iberia; iii) discuss potential sources; and iv) test the hypothesis of sedimentary recycling. U–Pb dating of zircons established a maximum depositional age for this deposit as Permian (ca. 296Ma), which is about sixty million years older compared to the fossil content recognized in previous studies (Upper Triassic). The distribution of detrital zircon ages obtained points to common source areas: the Ossa–Morena and Central Iberian zones that outcrop in and close to the Porto–Tomar fault zone. The high degree of immaturity and evidence of little transport of the Triassic sediment suggests that granite may constitute primary crystalline sources. The Carboniferous age of ca. 330Ma for the best estimate of crystallization for a granite pebble in a Triassic conglomerate and the Permian–Carboniferous ages (<ca. 315Ma) found in detrital zircons provide evidence of the denudation of Variscan and Cimmerian granites during the infilling of continental rift basins in western Iberia. The zircon age spectra found in Triassic strata are also the result of recycling from the Upper Carboniferous Buçaco basin, which probably acted as an intermediate sediment repository. U–Pb data in this study suggest that the detritus from the Triassic sandstone and conglomerate of the Lusitanian basin is derived from local source areas with features typical of Gondwana, with no sediment from external sources from Laurussia or southwestern Iberia.

Numerical modelling of multi-pass solar dryer filled with granite pebbles for thermal storage enhancement

In this paper, a theoretical modelling of a cheap solar thermal dryer for small and medium scale farmers with multi-pass approach has been investigated. Comsol Multiphysics modelling tool was employed using numerical technique. The rock particles were used to enhance the thermal storage of the drying system. The local weather data were used during the simulation while parameters and coefficients were sourced from literature. An improvement on efficiency of up to 7% was recorded with error of 10-5 when compared with the reported double pass solar collector. A fair distribution of hot air within the cabinets was also achieved. Though the modelling tool used was robust but the characterization of the system materials need to be done to improve the system accuracy and better prediction.

Zircon provenance in meta-sandstones of the São Roque Domain: Implications for the Proterozoic evolution of the Ribeira Belt, SE Brazil

Detrital zircons from quartzites of the São Roque Domain were subject of studies of crystal growth and stratigraphy, using in situ LA-ICPMS trace element geochemistry and U–Pb dating to deduce their provenance and contribute to understand the tectonic evolution of the Proterozoic metasedimentary successions of southeast Brazil. Trace element chemistry of most detrital cores indicates derivation from plagioclase-rich felsic rocks (e.g., tonalites to granodiorites); however, a small proportion may derive from gabbroic sources, as indicated by a combination of features (strong positive Ce anomaly, high LuN/SmN, low U/Yb; concave-down shape of the intermediate REE patterns). Thin metamorphic overgrowths are chemically distinct (e.g., enriched in several trace elements, especially the LREE), and were dated at 584±47Ma, reflecting the Ediacaran metamorphism and granite magmatism that affected the São Roque Domain. The detrital zircon U–Pb ages for five quartzite samples from different stratigraphic positions within the São Roque Domain are restricted to the Paleoproterozoic and Archean (∼1730–3440Ma). A striking feature of the dataset is a main peak at ∼2.2Ga which is characteristic of all samples; the age and abundance of Archean peaks allow distinguish two groups of samples: Jaraguá and Japi, with 41–43% Archean zircons and a peak at 2.6–2.7Ga; and Voturuna, Pirucaia and Serra da Viúva, with 16–21% Archean zircons and a peak close to the Archean-Paleoproterozoic boundary (2.4–2.5Ga). A limited contribution of late Paleoproterozoic (Statherian) sources places an upper limit for the deposition of the sedimentary successions that is consistent with the estimated age of the metaconglomerate-metarkose rift sequence of the São Roque Group (Boturuna Formation), based on U–Pb dating of interlayered meta-trachydacites (1.75Ga). Our data demonstrate that the different sedimentary successions of the São Roque Domain have an essentially continental (cratonic) provenance which is very similar to those of other sequences in the Ribeira Belt (Açungui and possibly also Embu Domain). The ∼2.2Ga age of the volumetrically most important sources, also indicated by the age of granite pebbles in metaconglomerates, is a diagnostic signature, consistent with the age of regional basement (e.g., orthogneisses from few basement nuclei in the Açungui Domain). Similarities in provenance and tectonic evolution of the metasedimentary sequences are consistent with the interpretation that the Ribeira Belt is part of the reworked border of the São Francisco Paleoplate, displaced southwestward as a result of significant dextral orogen-parallel tectonics during the Neoproterozoic collision, and may imply that a suture zone between this paleoplate and another stable continental area to the SW lies below the Phanerozoic sediments of the Paraná Basin.

Cryogenic energy storage characteristics of a packed bed at different pressures

A packed bed cryogenic energy regenerator is investigated for use in a cryogenic energy storage (CES) system. With liquid nitrogen used as the working fluid, the cryogenic energy storage characteristics of the packed bed are investigated at pressures of 0.1 MPa and 6.5 MPa. The packed column is 1500 mm in height with a 345 mm inner diameter, and is made of 16 mm thick stainless steel. Granite pebbles about 9 mm in size are used as the medium for energy storage. The transient axial and radial temperature distributions of the packed bed were measured, and the results show that the transient temperature axial distribution exhibits a typical thermocline behavior at both low and high pressures. The temperature distribution does however vary significantly at the different pressures.