Low TiO2 Contents Research Articles

Late Jurassic Haobugao granites from the southern Great Xing’an Range, NE China: Implications for postcollision extension of the Mongol–Okhotsk Ocean

Abstract The Mongolia-Okhotsk tectonic regime had a significant impact on the tectonic evolution of Northeastern (NE) China. However, there is no consensus on the role of this regime in the geological evolution of the Xing’an Massif during the late Mesozoic. This article presents the results of zircon U–Pb geochronology, whole-rock major and trace-element geochemistry, and zircon Hf isotopic compositions for granites in the Haobugao area of the southern Great Xing’an Range, NE China, to determine their petrogenesis, source, and tectonic setting. The zircon U–Pb ages indicate that the granites crystallized at 152.7 ± 0.5 Ma. The granites exhibit high SiO2 (70.75–73.19 wt%) and K2O + Na2O (8.00–8.65 wt%) contents and extremely low MgO (0.40–0.59 wt%) and TiO2 (0.24–0.33 wt%) contents. They belong to the metaluminous, high-K calc-alkaline, and ferroan series, with mostly right-inclined REE curves, flat heavy rare earth element patterns, high 10,000 Ga/Al ratios, and intensely negative Eu anomalies. The Zr/Hf ratios are 24.2–27.7, Nb/Ta ratios are 6.4–8.9, and Y/NbN ratios are >1.2. These characteristics suggest an A2-type granite affinity. The zircon εHf values of the rocks range from +5.62 to +9.12, corresponding to T DM2 values of 621–906 Ma, indicating that juvenile materials in the Neoproterozoic may be a source of these granites. Geochemically, these Late Jurassic A2-type granites are similar to those from post-collision extension settings. The primary magma was likely derived from the partial melting of a delaminated region of the lower crust.

Titanium dioxide nanoparticles embedded in assembled dipeptide hydrogels for microfluidic photodegradation

Dipeptides can be self-assembled via non-covalent bonds towards functional nanostructures for diverse applications in nanotechnology. Here, we introduce a convenient microfluidics-guided dipeptide design as a platform for photodegradation of contaminants in water. Titanium dioxide (TiO2) nanoparticles (NPs) are chosen as photocatalysts due to their vastly studied properties. By using a well-defined microchannel architecture, the dipeptide N-fluorenylmethoxycarbonyl diphenylalanine (Fmoc-FF) and TiO2 NPs are efficiently mixed leading to a self-assembled Fmoc-FF hydrogel with embedded TiO2. Owing to shear-thinning and rapid self-healing of Fmoc-FF hydrogels, we can transfer and inject Fmoc-FF/TiO2 hydrogels into any other microdevice for specific applications, where these low-molecular-weight-gelator- (LMWG-)based Fmoc-FF hydrogels fill out the microchannel volume. Different morphologies of Fmoc-FF/TiO2 hydrogels are obtained by simple concentration screening of TiO2 NPs and Fmoc-FF. Owing to the density of the three-dimensionally twined Fmoc-FF nanofibers, solutions swelling the dipeptide hydrogel can be exchanged without leaching out TiO2 NPs. By further analysis, our hydrogel-filled flow cell can be employed for continuous-flow photodegradation in water under light irradiation. Especially, compared to the TiO2 NPs suspension, Fmoc-FF/TiO2 hydrogels with relatively low concentrations of TiO2 exhibit enhanced photodegradation capabilities due to better dispersion of nanoparticles. Such strategy provides a versatile platform for embedment of small inorganic catalysts or enzymes for (bio-)chemical conversion of solutes passing through the hydrogel network.

Study of the passivation and repassivation behavior of pure titanium in 3.5 wt% NaCl solution and 6 M HNO3 solution

We reveal differences in composition and structure of passive films and repassivation rate of titanium in 3.5 wt% NaCl and in 6 M HNO3. Titanium in 6 M HNO3 shows worse corrosion resistance than in 3.5 wt% NaCl due to higher defect concentration and lower TiO2 content despite the thicker passive film, which is the result of accelerated cathodic process and promoted dissolution/formation dynamic equilibrium of passive film in 6 M HNO3. Repassivation rate in 3.5 wt% NaCl is higher although film growth rate is lower, as the film exhibits good barrier effect when it is thin. Our results provide insights needed to guide application of titanium in SNFR plants.

Petrography and Geochemistry of the Baska Piwaza Ore Mineralization, Halgurd Mountain, Iraqi Kurdistan Region: Insights on the Genesis

This paper is the first attempt to study the mineralogical and geochemical features of mineralization hosted within the volcanic rocks of the Baska Piwaza section, at Halgurd Mountain, which is the highest mountain in Kurdistan and the whole of Iraq. The host lithologies in the studied section represent mostly volcanic rocks (basalts to andesites), and secondary sedimentary lithologies, such as radiolarian chert. There are two main stages of oxide and sulfide mineralization that can be recognized under three-time epochs which are early, middle and late stages that caused the formation of oxide and sulfides ore minerals. The most dominant oxide mineral is hematite, with minor contribution of magnetite, goethite, and rutile. In terms of sulfides, pyrite is the predominant mineral phase with secondary contribution of chalcopyrite. The petrographic study and XRD data of the host volcanic rocks reveal that the most abundant minerals are plagioclase, K-feldspar, pyroxene, and amphibole, while the secondary minerals are quartz, calcite, clinochlore, sericite, prehnite, pumpellyite, and muscovite. Additionally, the radiolarian chert is comprised by quartz, hematite, calcite, ankerite, clay minerals, and apatite which is characterized by low silica content and high iron oxide. Low concentration of TiO2 ,and Fe2O3 are suggesting the quartz vein occurred with the volcanic rocks are formed due to low hydrothermal fluid. Field observation, petrographical and geochemical data indicate that the rocks of the Baska Piwaza section are influenced by hydrothermal alteration, due to the high value of Loss On Ignition (LOI) and the high ratio of alkalis (Na2O+K2O). Moreover, evidences of chloritization and sericitization of the mafic minerals, and feldspar minerals respectively support the hydrothermal impact.

Technological research of process for producing titanium rich slag and complex titanium-containing ferroalloy

This paper demonstrates the results on the experimental smelting of the titanium rich slag and complex titanium-containing ferroalloy under the large-scale laboratory conditions that simulate industrial one. The technological researches of the process were performed on an ore-thermal furnace with 200 kVA transformer power. The titanium rich slag was produced from the low-grade ilmenite concentrate, i.e. the low TiO2 content and the high content of impurities. During the production of the high-grade titanium slag (TiO2 content: 75–80%), the impurity elements are transferred into the associated alloyed metal (cast iron). Thus, it can be used to smelt the steel. As a result, samples of titanium slag have been produced with the content of the main components, %: TiO2 – 80.2; Al2O3 – 4.5; SiO2 – 1.97; Cr2O3 – 1.3 and Fe2O3 – 9.87. Then, in metallurgical practice a complex titanium-containing ferroalloy was first smelted from the previously produced titanium rich slag using a carbothermic approach. The high-ash coal was applied as a carbon-bearing reducing agent. The ash was more 45%. As a result of tests, a pilot batch of the alloy was produced with the following chemical composition, %: Ti - 20–25; Si - 35–45; Al - 10–15; C - 0.2–0.5; P - no more than 0.08; and ferrum. The main component content in the produced alloy suggests that it can serve as an alternative to a mechanical mixture (FeSi45, aluminum shavings, low-percentage ferrotitanium) for steel alloying and deoxidation purposes.

Chronolgy and Geochemistry of the Sijiaying Iron Deposit in Eastern Hebei Province, North China Craton: Implications for the Genesis of High-Grade Iron Ores

The Sijiaying iron deposit is located in the Eastern Hebei area of the southern section of the northern margin of the North China Craton (NCC) and is the largest single iron deposit in China. The deposit contains many banded iron formations (BIFs) and was proven to have more than 3 million tons of high-grade iron ore resources. This study carried out geochemistry and zircon U–Pb analysis of normal-grade iron ore, high-grade iron ore, and wall rock (biotite–leptynite, chlorite–sericite schist) in the Sijiaying deposit and discussed the genesis and metallogenic age of high-grade iron ore. BIFs have low concentrations of Al2O3 and TiO2 and high field strength element (HFSE) depletion, indicating almost no contamination via terrestrial debris. The standardized post-Archean Australian shale (PAAS) rare earth element (REE) distribution pattern indicates that the iron formation exhibits positive Eu, Y, and heavy rare earth element (HREE) anomalies and lacks negative Ce anomalies, indicating that the Sijiaying BIF was enriched with iron sources via high-temperature hydrothermal fluids from the seabed and deposited in an anoxic ancient marine environment. In addition, geological field work identified two types of high-grade iron ore in the mining area: primitive sedimentary and hydrothermally altered high-grade iron ore. Further ore geochemical research showed that the primitive sedimentary-type iron ore is similar in geochemistry to the BIF. In addition to low Eu/Eu* values, the hydrothermally altered high-grade iron ore shows geochemical characteristics similar to those of the BIF, suggesting that they share the same iron source but did not form at the same time. The total large ion lithophile element (LILE) (Sr, Ba, Pb) contents in primitive sedimentary-type high-grade iron ore are higher than those in hydrothermally altered high-grade iron ore, indicating that LILEs are carried away via fluids during the hydrothermal alteration process in normal-grade iron ore. The geochemical characteristics of biotite–leptynite and chlorite–sericite schist include high contents of SiO2 and Al2O3, light rare earth elements (LREEs), LILE enrichment (Rb, Ba, Sr, Zr), and HFSE depletion (Nb, Ta, P, Ti), characteristics that are similar to island arc volcanic rocks. The reconstruction of the original rock indicates that the wall rock is a product of volcanic sedimentary cycles in an island arc setting. Zircon cathodoluminescence images and LA–ICP–MS zircon U–Pb dating can be divided into four age groups (3283 Ma, 2547 Ma, 2500 Ma, and 2407 Ma), which correspond to the earliest volcanic activity in eastern Hebei, the main mineralization age of the Sijiaying BIF (the mineralization age of primitive sedimentary high-grade iron ore), a regional tectonic–metamorphic event, and the occurrence of migmatization (the mineralization age of hydrothermally altered high-grade iron ore), respectively. Therefore, the Sijiaying BIF and primitive sedimentary high-grade iron ores were deposited and mineralized at 2547 Ma, and the iron orebody was later altered via the hydrothermal solution at 2407 Ma, forming large-scale high-grade iron ores.

Lattice-preferred orientation (LPO) of olivine and amphibole in amphibole peridotites and neighboring hornblendites from Gapyeong, South Korea and implications for seismic anisotropy

Amphibole peridotites and neighboring hornblendites are often found in subduction zones. To understand the effect of amphibole-rich rocks on seismic anisotropy in subduction zones, we studied the lattice-preferred orientation (LPO) of olivine and amphibole in amphibole peridotites and neighboring hornblendites in Gapyeong, South Korea. The major minerals of amphibole peridotites were olivine (31–51% in volume), amphibole (28–47%), and orthopyroxene (7–16%). Amphibole in amphibole peridotites showed relatively high SiO2 and low TiO2 and Na2O contents (S-type amphibole), indicating that it was formed under supra-subduction conditions. Amphibole in amphibole peridotites showed the type-I, type-II, and type-IV LPO, whereas amphibole in neighboring hornblendites showed the type-III and type-IV LPO. In the case of olivine, most samples showed a mixture of A- and B-type LPO, and one sample showed a mixture of B- and C-type LPO. Many serpentine inclusions were found in olivines. Fourier-transform infrared (FTIR) analysis of the samples showed that the olivines contained a large amount of water (∼29000–45000 ppm H/Si). We also found many dislocations in olivines. These observations indicate that samples showing a mixture of A- and B-type LPO and a mixture of B- and C-type LPO of olivine were deformed under water-rich conditions by dislocation creep. In amphibole peridotites, the P-wave anisotropy of olivine was relatively low (0.9–4.8%), whereas the P-wave anisotropy of amphibole was high (6.5–17.7%). The maximum S-wave anisotropy of olivine was also relatively low (0.87–2.89%), whereas the maximum S-wave anisotropy of amphibole was high (3.81–15.19%). In hornblendites, the P-wave anisotropy and maximum S-wave anisotropy of amphibole were high (6.9–13.6% and 4.27–10.61%, respectively). The P-wave anisotropy and maximum S-wave anisotropy of the amphibole peridotites were in the range of 2.6–8.4% and 1.73–7.30%, respectively. The seismic velocity and anisotropy pattern of amphibole peridotites were more similar to those of amphibole than those of olivine, indicating that the seismic properties of amphibole peridotites were more strongly affected by amphibole than by olivine. Furthermore, the seismic anisotropy of the mixture of amphibole peridotite and hornblendite in subduction zones was also found to be significantly affected by the amphibole LPO in hornblendite.

Fe-Si-C isotope constraints on the genesis of iron ores in Gongchangling iron deposit in northeastern China

The Gongchangling iron deposit is an oxide-facies Algoma-type banded iron formation (BIF) and one of the most representative iron deposits in northeastern China. We present new data from petrological, whole-rock geochemical, and Fe-Si-O isotope compositional data from the Gongchangling BIFs to constrain the origin of ore-forming materials and mineralization processes. The low Al2O3 and TiO2 contents in iron ores indicate that the sources of the BIFs were not contaminated by terrigenous clastic sediments. The Gongchangling BIFs are characterized by depletions in LREEs and 30Si and enrichments in HREEs, with positive Eu and Y anomalies. Given these and the Fe isotope results, we conclude that both high-temperature hydrothermal fluid and seawater contributed to the formation of the BIFs and that a mixture of seawater and ~ 0.1 % hydrothermal fluid, which percolated and dissolved the submarine volcanic rocks, provided the ore-forming materials. Combining the Ce anomalies, enrichments in heavy Fe isotopes and low δ13C compositions, we conclude that the fO2 of Archean seawater was limited. Integrated petrographic and geochemical evidence indicates that the high-grade iron ores from the Gongchangling BIFs experienced incomplete oxidation and low amounts of Fe precipitation in a marine environment and that dissimilatory iron reduction and metamorphic hydrothermal fluid played important roles.

Effect of TiO2 on mechanical and thermal properties of Al2O3-based coating via atmospheric plasma spraying

ABSTRACT In this study, Al2O3-based coatings with varying TiO2 contents (0, 3, 13, and 40%) were fabricated using atmospheric plasma spraying technique. To compare the superiority of the samples, their mechanical (Vickers hardness and adhesion strength) and thermal properties (thermal conductivity and thermal shock resistance) were characterized. As observed, Al2O3-40%TiO2 (A-40T) coating exhibited relatively inferior mechanical properties but superior thermal insulation and thermal shock resistance at 600°C. According to the microstructure and phase analysis, this finding is attributed to the special phase, Al2TiO5, and preexisting microcracks inside the coating. Thus, A-40T manifested excellent characteristics for thermal insulation application compared with pure Al2O3 and low-TiO2 content coatings.

Origin of high-Cr podiform chromitites from Kabaena Island, Southeast Sulawesi, Indonesia: constraints from mineralogy and geochemistry

ABSTRACT The East Sulawesi Ophiolite, one of the three largest ophiolites in the world, contains important podiform chromitites. However, the origin of these chromite deposits is not well constrained. Here, we present the detailed mineralogy and in situ chemistry of chromite and solid inclusions within chromite for podiform chromitites from the Kabaena Island, Southeast Sulawesi. Chromite grains have low TiO2 (0.17–0.27 wt%) and Al2O3 (13.4–15.1 wt%) contents and high Cr# [Cr/(Cr+Al), molar] of 0.70–0.74 and Mg# [Mg/(Mg+Fe2+), molar] of 0.69–0.75, which resemble those of other high-Cr podiform chromitites worldwide. The MORB-normalized patterns for some selected major-trace elements of chromite show slightly positive slopes from Al2O3 to Mn. Chromite-hosted silicate inclusions include olivine, clinopyroxene, orthopyroxene and amphibole and are characterized by higher Mg/Fe ratios than those of host peridotites. The geothermobarometry of chromite-hosted clinopyroxene-orthopyroxene pairs indicates that the estimated T-P conditions of the parental magma of the Kabaena chromitites are 950–1010°C and 7.0–8.4 Kbar. The extreme-Mg-rich olivine inclusions (Fo >96) with extremely high Ni (5300–8200 ppm) and Cr (1500–6700 ppm) contents are interpreted to have crystallized from high-Mg and Cr boninitic melts, and the Fo contents were then elevated by subsolidus re-equilibration (Fe–Mg and Fe–Ni exchange) with chromite. Sulfide inclusions contain base metal minerals containing millerite with rare pentlandite and chalcopyrite, and platinum-group minerals that include the laurite-erlichmanite series, Ir–Ni monosulfide, irarsite and cuproiridsite. This sulfide assemblage reveals that their parental magmas experienced the evolution of high T and low f(S2) to low T and high f(S2) from the early to late stage. Finally, combined with the palaeogeographic reconstruction in Sulawesi, we propose that the high-Cr chromitites in this region were formed by the reaction of depleted mantle and boninitic magma beneath a juvenile island arc, implying the initiation of a new subduction in the Miocene.

Geochemical constraints on the multistage evolution of the Yilashan ophiolite, central Tibet

The Yilashan ophiolite in the southern part of the central Bangong-Nujiang suture zone comprises variably deformed harzburgite, dunite, and less abundant gabbro and pyroxenite pods and crosscutting veins. Cr-spinels in podiform chromitite bodies are characterized by high Cr# (64.3–74.3), high Mg# (58.2–67.5), and consistently low contents of TiO2 (≤0.12 wt%). Primary melt calculations designate parental boninitic magmas with Al2O3(liquid) contents of 11.67–13.49 wt%, and (FeO/MgO)liquid values of 0.92–1.12.Whole-rock geochemical data of fresh pyroxenite samples are characterized by negative K, Ta, Nb and Zr anomalies, no Eu anomaly, and chondrite-normalized REE patterns comparable to the N-MORB melts. The gabbro samples, in contrast, are high-K calc-alkaline, with elevated contents of LILE (Rb, K, Th) and depleted HFSE (i.e., Nb, Ta, P, Ti), consistent with subduction-related magmas. The fractionated chondrite-normalized REE patterns, high LREE/HREE values, and negative Eu anomalies of these gabbroic rocks are similar to the island arc basalts. Pyroxenite shows high PPGE/IPGE values, variable Pd/Ir (55.7–316.7), and left-leaning primitive mantle-normalized PGE pattern, whereas massive chromitite is enriched in IPGE relative to PPGE. The PGE patterns of pyroxenite and chromitite, though distinct, depict significant fractionation and partial melting in their formation. The elevated contents of PPGEs in pyroxenite suggest derivation from sulfur-saturated magmas as chromitite crystallization scavenged the compatible IPGEs from the parental melt. This assumption is supported by clinopyroxene in pyroxenite with variable Al2O3 contents and variable Cr2O3 contents (0.32 to 0.73 wt%). For the fractionated gabbro unit, zircons yielding a concordia U-Pb age of 162.8 ± 3.0 Ma and widely variable εHf(t) values (−9.2 to +12.0) suggest formation from heterogenous or reworked source materials during a Middle Jurassic subduction increment in the Neo-Tethyan Ocean.

Gabbroic Rocks in Mawat Ophiolite Complex, NE Iraq: Geochemical Constraints on their Tectonogenesis

The Mawat Ophiolite Complex located in north-eastern Iraq represents part of the Iraqi Zagros Suture Zone, located at the border between the Arabian-Iranian plates. It consists of peridotite, gabbro, subvolcanic sheeted dykes and volcanic pillow lava. The geochemical signatures of the gabbro show a significant variation in major elements concentration, low concentrations of TiO2 (0.06-0.36 wt.%), Na2O (0.44-0.98 wt.%), K2O (0.024-0.48 wt.%), P2O5 (0.002-0.009 wt.%) and moderate variations in SiO2 (46.13-53.77 wt.%) with wide ranges and high concentration of Al2O3 (13.87-22.18 wt.%), Fe2O3 (0.04-2.95 wt.%), FeO (2.68-8.76 wt.%), MgO (8.09-14.28 wt.%) and CaO (11.08-17.04 wt.%). The flat REE patterns of the present rocks represent island arc tholeiite (IAT) tectonics and a subduction-related environment. The main features of the magma generated in the supra subduction zone are the enrichment of LILEs and depletion of the HFSEs and the strong negative Nb anomaly. Geochemical evidence indicates that the tholeiitic gabbros were generated in an arc-related tectonic setting. The tectonomagmatic diagrams for gabbros and the very low Ti content propose that the gabbroic rocks of Mawat Ophiolite have island arc tholeiitic (IAT) and possibly boninitic affinities which have a related to the supra-subduction zone (SSZ).

Petrography and geochemistry of the iron-rich rocks in the banded iron formation of the Chilpi Group, Central India: Implications on the level of oxygen in the Paleoproterozoic atmosphere before the “Proterozoic iron ore gap”

The Chilpi Group (2050–1850 Ma) in the Bastar Craton contains Banded Iron Formation (BIF) deposited immediately after the Great Oxidation Event but before the “Proterozoic iron ore gap”. Baseline geochemical data generated from this crucial period of Earth's history representing the transition from an initial high productivity period followed by productivity collapse, thereby delaying the evolution of biota, are interpreted in terms of the redox state of the ocean and atmospheric oxygen content. Presence of chamosite, greenalite and siderite in the ironstones of the Chilpi Group, identified during present analysis, provide valuable information regarding the redox state of the shallow sea. Geochemical analyses reveal high concentrations of Fe2O3total and SiO2 (average ~ 87.85 wt%) in iron-rich bands. Trace elements commonly enriched in detrital phases (e.g. Sc, Hf, Nb, Th and Zr) show good correlation with total REE concentration, but these have concentration below the cut-off limit defined for detrital sediments (except 3 samples). Higher concentration of these elements in greenalite/chamosite-rich samples indicates accumulation of these elements in greenalite/chamosite during primary precipitation. Most of the samples have low concentrations of Al2O3 (<5 wt%) and TiO2 (<0.5 wt%), but some chamosite-bearing samples show enrichments of Al2O3 (up to ~20 wt%). Post-Archean Australian Shale normalised rare earth elements with Y (REEY) patterns, showing a superchondritic Y/Ho ratio (average 32.15) and positive La, Gd and Y anomalies, indicate the preservation of seawater like signatures. Though a low positive Eu-anomaly, and Al/(Al + Fe + Mn) versus Fe/Ti plot suggest seawater signature with possible mixing of hydrothermal fluids and/or <10 % detrital components, preservation of seawater signatures and no involvement of high-temperature hydrothermal fluids are deduced from Eu/Sm versus Sm/Yb and Eu/Sm versus Y/Ho patterns. The Eu/Sm and Y/Ho ratios lower than the seawater and a mixing trend away from oceanic hydrothermal solution indicate possible mixing of freshwater with seawater for the observed REEY patterns. Redox-sensitive trace element ratios indicate a dysoxic to suboxic-anoxic condition in the depositional basin. Presence of oolitic textures and occurrence of chamosite support the shallow water (<60 m water depth) and anoxic condition in the depositional basin. The oxygen content of 10−3–10−5 times the present atmospheric level in the atmosphere is inferred for the period during the deposition of the BIF.

The earliest Neoproterozoic Nb-enriched mafic magmatism indicates subduction tectonics in the southwestern Yangtze Block, South China

To better reveal the early Neoproterozoic tectonic process of South China with respect to the assembly of the Rodinia supercontinent, an integrated dataset of geochronology, whole-rock geochemistry, and Sr-Nd-Hf isotopic compositions for diabases that intruded the Kunyang Group in the southwestern Yangtze Block is herein presented. Zircon U-Pb dating gives four weighted mean 206Pb/238U ages of 946 ± 4 Ma, 948 ± 6 Ma, 939 ± 4 Ma, and 918 ± 7 Ma, suggesting mafic magmatism in the earliest Neoproterozoic. The diabases possess Nb = 12.3–30.5 ppm, Nb/U = 19.99–37.06, Nb/La = 0.78–1.05, (Nb/Th)PM = 0.44–0.80, and (Nb/La)PM = 0.75–1.02, geochemically resembling those of typical Nb-enriched basalts. They are tholeiitic in composition with low SiO2 (49.49–51.95 wt%), high TiO2 (2.03–4.65 wt%), MgO (2.50–6.14 wt%), and Fe2O3T (15.38–18.84 wt%) contents. They are enriched in light rare earth elements (LREEs) with weak negative Eu anomalies (Eu/Eu* = 0.75–0.96) and show E-MORB-like characteristics with slight to moderate Nb-Ta depletion. The samples show zircon εHf(t) values ranging from + 5.8 to + 10.3 and whole-rock εNd(t) values from + 0.5 to + 0.9. These elemental and isotopic characteristics suggest that the 0.95–0.92 Ga diabases may have derived from an E-MORB-like magma source with the injection of metasomatized slab melts. Integrating previous studies with our results, we propose that the southwestern Yangtze Block evolved from an intracontinental rift to a passive continental margin in the late Mesoproterozoic, followed by the development of an earliest Neoproterozoic continental arc-back-arc basin system analogous to the Northern Okinawa Trough. The distinct tectonic processes between the southern and northern parts of the Yangtze Block at ca. 1.0–0.9 Ga favour the hypothesis that the final cratonization of the present-day Yangtze Block occurred slightly later than ∼ 0.9 Ga in response to the Rodinia supercontinent assembly.

Investigation of toxicity of TiO2 nanoparticles on glioblastoma and neuroblastoma as the most widely used nanoparticles in photocatalytic processes

Background: Titanium dioxide (TiO2 ) nanoparticles (NPs) are among the most important and usable photocatalysts. Recently, the biological properties of these NPs, particularly, its anticancer activity, have been considered. Glioblastoma and neuroblastoma are two fatal brain tumors with a high mortality rate in humans, the hope for treatment of which is weak by the common methods. Methods: In this study, the cytotoxicity effects of TiO2 alone and in combination with ultraviolet A (UVA) irradiation on two different cell lines, neuroblastoma (SH-SY5Y) and glioblastoma U87, were investigated. After administration of 10, 50, 100, and 500 μg/mL TiO2 , 0.043 and 1.4 mW/cm2 UVA irradiation, cell viability was investigated after 4, 24, and 48 hours by 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assay. Results: MTT assay and light microscope demonstrated that the effect of TiO2 NPs varied based on the dose of the substance, the impact time, the cell type, and the amount of radiation. In this study, for NPs alone, both toxicity and non-toxicity of the substance were observed. For NPs in the presence of UV, based on the comparison with its status alone and the difference in the viability assay of the two groups, both the photocatalytic and the coating effect of the NPs were observed. Conclusion: According to the results, different concentrations of TiO2 can be used for different purposes. Low concentrations of TiO2 can be used to increase the efficiency of photodynamic therapy and high concentrations of TiO2 can be used to protect the normal cell. This strategy improves the photodynamic therapy and reduces the harmful effects.

Some Mineralogical Characteristics of the Egyptian Black Sand Beach Ilmenite Part I: Homogeneous Ilmenite and Titanhematite-Ferriilmenite Grains

The high-grade Egyptian beach ilmenite concentrate contains various mineral textures in addition to the main homogeneous ilmenite grains (63%), which may contain solid solutions of geikielite (MgTiO3) and pyrophanite (MnTiO3) mineral components. Few homogeneous ferrilmenite grains (2%) associated with the concentrated ilmenite grains are detected. The contents of Fe2O3, MgO, Al2O3, and Cr2O3 in the ferrilmenite grains range between 7.3% and 22.8%, 3.4% and 6.6%, 0.2% and 0.7%, and 0% and 1.2% respectively. The detected hematite-ilmenite exsolved intergrowths (21.4%) have titanhematite exsolutions of different shapes, sizes, and orientations. They occupy 5%-40% of the whole intergrowth and may show one or two distinct generations. In some ferrilmenite components, MnO ranges between 1.5% and 8.6%. The Cr2O3 and Al2O3 contents range between 0% and 1.2% and 0% and 3.2% respectively. They are mostly between 0% and 0.1% for either of the ferrilmenite components, while relatively greater content is present in the titanhematite components. In some grains, the titanhematite exsolution bodies are replaced by goethite or hydrated iron oxides. In others, the ferrilmenite intergrowth may be partially or completely altered into leucoxene. Some minor composite grains are detected in the concentrate, where each grain consists of two parts, one part is titanhematite-ferrimenite and the other is ferrilmenite-titanhematite. The titanhematite exsolved components have relatively lower TiO2 content (5.8%-23.8%). Both MgO and MnO are positively correlated with FeO rather than Fe2O3. The presence of sphenes in the obtained ilmenite concentrate may be responsible for the recorded amounts of SiO2 (30.1%-30.8%) and CaO (28.1% and 28.8%). The Cr2O3 content is relatively much higher in sphene spots than in ilmenite spots, ensuring that Cr2O3 neither follows TiO2 nor FeO. The nature of the problem of the relatively lower Ti content and the relatively higher Fe and Cr contents of the obtained ilmenite concentrates is the target of the article. The problem is related to the mineralogy of ilmenite or to the used physical concentration flowsheet of the separated concentrate and the ability to improve the ilmenite concentrate’s specifications. It is concluded that although the homogeneous ilmenite is characterized by low Cr2O3 content, some of the other exsolved texture components, e.g. titanhematite and sphenes, have relatively higher Cr2O3, in addition to Fe2O3, SiO2, or CaO. They can negatively affect the marketable specifications of the separated Egyptian black sand ilmenite concentrate.

An Effusive Lunar Dome Near Fracastorius Crater: Spectral and Morphometric Properties

We examine a dome within the boundary between Fracastorius crater and Mare Nectaris. The dome has a noticeable vent structure and appears to be perpendicular to wrinkle ridges in the southern Mare Nectaris basin. The spectral signature of this dome, derived from Clementine UVVIS and Chandrayaan-1 M3 reflectance data, revealed that Fracastorius has low TiO2 content and primarily basaltic material. Using altimeter data, we measured the dome diameter to be 28.6 km, with a dome height of 241.5 m, and a flank slope of 1°. Based on rheological modeling of the dome and a viscoelastic model of the presumed feeder dike, we obtained a magma viscosity of 3.1 × 105 Pa s, an effusion rate of 5.9 m3 s−1, a duration of multiple effusion processes of 4.15 years, and a magma rise speed of 2.1 × 10−4 m s−1. From these measurements, we estimate the feeder dike geometry to have a horizontal dike length of 234 km and a width of 11.8 m. A comparison of the Fracastorius dome with other noted lunar domes with similar morphometric properties reveal similar magma viscosities to domes found near craters Mee, Milichius and Petavius.

Ordovician continental arc magmatism in the Tam Ky‐Phuoc Son Suture Zone, Central Indochina Block, Southeast Asia

The Indochina Block is considered as a part of the Indian and Australian margins of Gondwana, and the Tam Ky‐Phuoc Son Suture Zone (TPSZ) lies in its central region as the boundary between the Truong Son Belt and Kon Tum Massif (KTM). However, the early Palaeozoic tectonic nature and timing of magmatism within the TPSZ are still controversial. To tackle the issue, we present herein the zircon U–Pb ages with their trace‐element compositions of five dioritic–granitic granitoids in the TPSZ. U–Pb age dating of magmatic zircons from them suggests emplacement ages of ca. 447–450 Ma. Whole‐rock geochemistry of the samples shows low TiO2 contents (0.36–1.18 wt%) and Mg# (42.04–53.07). They display enrichment in light rare earth elements ([La/Yb]N = 4.10–15.19), pronounced negative Nb, Ta and Ti anomalies relative to the chondrite‐normalized rare earth element patterns and primitive mantle‐normalized trace‐element distribution diagrams. The whole‐rock geochemical characteristics together with zircon trace‐element compositions from the same samples revealed their petrogenesis of a continental arc tectonic setting. Combining the results from this study together with available data from the TPSZ and its neighbouring units, we suggest accretionary orogenesis was responsible for generation of the Ordovician magmatic arc in the KTM, which will provide better understanding of the Early Palaeozoic evolution of the eastern Indochina Block.

Petrogenesis of the Triassic Sihaiping granite in the South Qinling orogen, central China: Implications for Mo-W mineralization

Late Triassic granites and related magmatic-hydrothermal Mo-W mineralization are common in the South Qinling orogen of central China, for which the Sihaiping granite pluton is a typical example. However, the petrogenesis of the Sihaiping granite remains enigmatic. Unraveling its petrogenesis can aid in our understanding of the Mo-W metallogeny in the South Qinling orogen. In this study, we present in situ zircon U-Pb ages, whole-rock geochemistry, and Sr-Nd-Hf isotopes of the Sihaiping granite. Zircon U-Pb dating by laser ablation inductively coupled plasma mass spectroscopy yielded Late Triassic ages of 206.6 ± 0.94, 206.5 ± 0.96, and 205.9 ± 0.75 Ma. The granite displayed high SiO2, K2O, and Rb contents, but low MgO, P2O5, TiO2, Sr, Ba, and Eu contents, indicating highly fractionated I-type granite affinity. The magma was interpreted to have been derived from Proterozoic crystalline basement in the South Qinling given its relatively low (87Sr/86Sr)i (0.704006 to 0.705039), negative εNd(t) (–4.9 to –3.5), and zircon εHf(t) (–6.2 to +1.6) values, with Nd model ages ranging from 1.39 to 1.27 Ga and two-stage Hf model ages ranging from 1.36 to 1.04 Ga. The strong fractional crystallization and suitable oxygen fugacity (ΔFMQ values mainly concentrated between +2 to +8) in the magmatic system played a major role in the Mo-W mineralization, indicating that the pluton has significant Mo(-W) metallogenic potential. Overall, the findings suggest that the Triassic Sihaiping granite and its related Mo-W mineralization likely formed in the transitional stage from syn- to post-collision between the South China Block and South Qinling along the Mianlue suture.

Geochemistry and geochronology of multi-generation garnet: New insights on the genesis and fluid evolution of prograde skarn formation

Origin of garnet in skarn (magmatic vs. hydrothermal) and the prograde skarn fluid evolution are still controversial. Two generations of garnet (Grt1, Grt2) were identified at the Tongshankou deposit: Grt1 is anisotropic with oscillatory zoning and resorbed boundary, whilst Grt2 grew around Grt1 and formed oscillatory rims. In-situ LA-ICP-MS U-Pb dating of Grt1 and Grt2 yielded a lower intercept 206Pb/238U age of 142.4 ± 2.8 Ma (n = 57; MSWD = 1.16) and 142.3 ± 9.6 Ma (n = 60; MSWD = 1.06), respectively, coeval with the ore formation and ore-related granodiorite emplacement. Positive Eu anomaly, non-CHARAC Y/Ho value and low TiO2 content, together with the mineral assemblages indicate that both Grt1 and Grt2 have a hydrothermal origin. The existence of melt and melt-fluid inclusions in Grt1, together with similar LREE-enriched patterns to the granodiorite, further indicate that Grt1 may have formed in the magmatic-hydrothermal transition. Higher U contents and LREE-enriched patterns of Grt1 indicate that fluid I is mildly acidic pH and low fO2. The inner gray Grt2 rims (Grt2A) is HREE-enriched with low U contents, indicating that fluid II has nearly neutral pH and high fO2. The wider Y/Ho range and LREE-enriched patterns of the outer light-gray Grt2 rims (Grt2B) show that the evolved magmatic fluid II had mixed with an external fluid, characterized by being mildly acidic pH and with high fO2. Our results suggest that the prograde skarn-forming fluids can be multistage at Tongshankou, and the mixing of meteoric water may have been prominent in the prograde skarn stage.